DISCRIMINATION PROHIBITED-Under the provisions of applicable f)ubliclaws enacted by Congress since 1964, no person in the United Statesshall, on the grounds of race, color, national origin, handicap, or age, beexcluded from participation in, be denied the benefits of, or be subjectedto discrimination under any program or activity (or, on the basis of sex,with respect to any educationaT program or activity) receiving Federalfinancial assistance. In addition, Executive Order 1J J41 prohibits discrimi­nation on the basis of age by contractors and subcontractors in the perfor­mance of Federal contracts, and Executive Order J 1246 states that nofederally funded contractor may discriminate against any employee orapplicant for employment because of race, color, religion, sex, or nationalorigin. Therefore, the National Institute of Environmental Health Sciencesmust be operated in compliance with these laws and Executive Orders.

Volume 103, Number 11, November 1995

980 In This Issue

PerspectivesEditorial

982 Ramazzini: Father of Environmental HealthGary E. R. Hook

984 CorrespondenceScience Funding . .. Oxygen Radicals . .. MTBE . .. Chemical Synergism

Commentary988 Chelation ofToxic Metals: Current Interests

Robert A. Goyer

Environews990 Forum

NIEHS News996 Modeling Macromolecules

Focus998 The Cancer Conundrum1006 Rethinking Recycling

Spheres of Influence1010 What Cost Environmental Health?

Innovations1014 In Vitro Innovations

Research

Review1018 The Risk of Childhood Cancer from Intrauterine and Preconceptional

Exposure to Ionizing RadiationRichard Wakeford

Articles1026 Sidestream Tobacco Smoke Exposure Acutely Alters Human Nasal Mucociliary Clearance

Rebecca Bascom, Jana Kesavanathan, Thomas K Fitzgerald, Kuo-Hsi Cheng, and David L. Swift

1032 Biological Monitoring of Iodine, a Water Disinfectant for Long-term Space MissionsGrazyna Zareba, Elsa Cernichiari, LowellA. Goldsmith, and Thomas W Clarkson

1036 Environmental Urban Lead Exposure and Blood Lead Levels in Children ofMexico CityIsabelle Romieu, Tania Carreon, Lizbeth Lopez, Eduardo Palazuelos, Camilo Rios, Yves Manuel, andMauricio Hernandez-Avila

1042 Potential for Bias in Epidemiologic Studies That Rely on Glass-based RetrospectiveAssessment of RadonC.R. Weinberg

Meeting Report1048 Role ofChelating Agents for Prevention, Intervention, and Treatment ofExposures to Toxic Metals

R.A. Goyer, MG. Cherian, MMJones, andJR. Reigart

1054 New Books1056 CalendarJ058 Fellowships, Grants & AwardsJ060 Position Announcements1064 Editorial Policy and Instructions to Authors

Environmental Health _

Qers~etl\/E=SJournal of the NatiOna'::I~ln=st=itut:':.~O::;fE~nV~ir":on~m~.n-ta;1H~"=lth:::;:Sc=i.=nce~s~-------------

Kenneth Olden, PhD

EDrr1JlIHl-CH& Gary E. R Hook, PhD, DSc

IloAIII Of AssoaAn EDr10lIs EuIa Bingham, PhDProfessor ofEnvironrnenal Health, University ofCincinnati Medical CollegeCincinnati, Ohio, USA

Patricia A. Buffier, PhDDean, Professor ofEpidemiologyUniversity ofCalifOrniaBerkeley, CalifOrnia, USA

John Cairns, Jr., PhDDistinguished Professor ofEnvironrnenal BiologyVuginia Polyrechnic Instimre aod State UniversityBlacksburg, Vuginia, USA

Molly J. Coye, MD, MPHSenior Vice President, Health Dimensions CorporationSao Jose, CalifOrnia, USA

Patricia K. Donohoe, MDDirector, Pediatric Surgical Research LaboratotiesMassachusetts Geneal Hospial, Boston,Massachusetts, USA

Jacobo Finkelman, MD, MPHDirector, Public Health Research DepartmentPan Ameticaa Center for Humao Ecology and HealthMexiro City, Mexiro

Bernard D. Goldstein, MDDirector, Environrnenal and OccupationalHealth Sciences InstimrePiscataway, New Jersey, USA

Philip C. Hanawalt, PhDProfessor of Biology, Stanfotd UniversityStanford, California, USA

Margaret L. Kripke, PhDPtofessor and Chair ofImmunologyM. D. Anderson Caoeer CentetUniversity ofTexasHouston, Texas, USA

Mortimer Mendelsohn, MD, PhDVice Chair, IUdiation EffectsResearch FoundationHiroshima, Japan

Michd Mercier, PhDDirector, International Programme on Chemical SafetyWorld Health OrganizationGeneva, Switzerlaod

George W. Lucier, PhD

Kenneth Olden, PhDDirector, National Instimte ofEnvironrnenalHealth SciencesResearch Triaogle Park, North Carolina, USA

Frederica P. Perera, DrPHAssociate Professor, Columbia University School ofPublic HealthNew York, New York, USA

Caodace B. Pen, PhDVISiting Professot, Center for Molecular aodBehavioal NeuroscienceRutgers University, Newark, New Jersey, USA

David P. Rall, MD, PhDAssistant Surgeon General, Retired USPHSWashington, DC, USA

Martin Rodbdl, PhDNational Instimte ofEnvironrnenal Health SciencesResearch Triaogle Park, North Carolina, USA

RadimJ. Stirn, MD, DScPrague Instimte ofAdvanced SmdiesPrague, Czech Republic

Takashi Sugimura, MDPresident EmerilUS, National Caocer CenterTokyo, Japan

Andrew Szczeklik, MD, PhDChairman, Department of MedicineUniversity School of Medicine in KrakowKrakow, Poland

Lorenzo Tomaris, MDEcully, France

Masaaki Terada, MDDirectorNational Caocer Center Research InstimteToykyo, Japao

Arthur C. Upton, MDClinical Professor of Pathology and RadiologyUniversity of New Mexiro School ofMedicineSanca Fe, New MexiOl, USA

Eliz.abeth K. Weisburger, PhD, DScBethesda, Maryland, USA

Mary Vore, PhDProfessot of Pharmarology and ToxirologyUniversity of Kenmcky, Lexington, Kenmcky, USA

EoITORlAl.IlmEW BOARD Philip W. AlbroJ. Carl BarrettLinda S. BirnbaumJames A. BondGary A. BoormanJoseph D. BrainDouglas W. BristolJohn R. BucherLeo T. BurkaRobett E. ChapinRajendra R. ChhabraColin F. ChignellEllis B. CowlingJames D. CrapoTerri DamstraTheodora R. DevereuxRichard T. Di GiulioRichard P. DiAugustineDarlene DixonJohn W. DrakeJune K DunnickDavid L. EatonEdward M. EddyMichael R. ElwellLinda E. FisherThorsten A. FjeUstedtW. James FlemingJames R. FoursBruce A. FowlerThomas J. GoehlJoyce A. GoldsteinThomas Goldswotthy

Roben A. GoyerPhilip E. HamrickJoseph K. HasemanJerrold J. HeindelErnest HodgsonDavid G. HoelJau-Shyong HongJames HuffHarvey JeffriesAnton M. JettenMarian Johnson-ThompsonBurke H. JuddNorman L. KaplanDavid G. KaufmanKenneth S. KorachThomas A. KunkelRobett LangenbachJoellen LewtasRobett E. LondonMichael I. LusterPenelope K. ManascoRobett MaronpotRonald P. MasonH. B. MatthewsRoger O. McClellanJames D. McKinneyJohn A. MclachlanDonald I. McReeMichelle A. MedinskyRonald L. MelnickScott E. MerkleElizabeth Murphy

Richard M. PhilpotWalter W. PiegnrschJames A. PoppChristopher J. PottierJohn B. PritchardJames W. PurneyJennifer M. RatcliffeJerry A. RobinsonWalter J. RoganVuginia M. SandersDale P. SandlerAnne P. SassamanDavid A. SavitzJames K. SelkirkMichael D. ShelbyCarol A. ShreffierJohn G. StanleyWilliam S. StokesWilliam A. SukJames A. SwenbergJackA. TaylorRaymond W. TennantClaudia ThompsonHugh TilsonKenneth R. TindallGregory S. TravlosUsha VaranasiClarice R. WeinbergMolly R. WhitwotthErrol Zeiger

On The Co.er: Ramazzini(1633-17141, recognized as thefather of occupational medi·cine through the publication, in1700, of his book De MorbisArtificum Distribs, is a strongcontender for the title of fatherof environmental health IseeEditorial, p. 982).

Environmental Health Perspectives

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publishing the most important developments in the environmental healthsciences arising from conferences, symposia, and workshops.

For subscription information, see p. 1058.

In This IssueWhat's Causing Cancer?In the war against cancer, incidence andmonality cates of some cancers continue to

increase. and scientists continue to searchfor answers abour causarion. Integral ro rhisdebare is rhe quesrion of whar role environ­mental facrors play in rhe cancer crisis. Inrhe first Focus anic1e (p. 998), experts onboth sides commenr on the currenr stare ofrhe knowledge and rhe possible impacr ofpesricides. air pollurion. environmenraltobacco smoke, metals, and radioactivity onrhe development ofcancer.

Sorting out Recycling

Every day Americans durifully sorr theirtrash and fill rheir separare bins wirh glass,plasric, paper, and other reusable wasres,with the assumprion that recycling is eco­nomically sound and environmenrallyfriendly. Alrhough advocares poinr ro rhedecreased need for landfills and rhe conser­varion of foresrs as evidence of recycling'sbenefits, critics emphasize thar recylingsometimes requires more energy, and is lesseconomical, than using virigin materials.The second Focus arricle (p. 1006) rakes acrirical look at the advantages and disad­vanrages of recyling ro assess irs true value.

Better Toxicity Tests

The quesr for alrernarives ro animal tesringconrinues. Recently developed skin and eyeanalogs. discussed in Innovations (p.1014), allow a variety of soluble and non­soluble materials ro be rested withour usinganimals. An added benefit is that rhese invitro systems provide information ahommechanisms of action of roxic responses.These sysrems take on additional impor­rance as 1998 approaches, the year theEuropean Commission expects all cosmer­ics companies to test their products usingin vitro methods when possible.

Childhood Cancer andRadiation

Wakeford (p. 1018) reviews the risk ofchildhood cancer from exposure of preg­nant women to ionizing radiation andrepom rhat epidemiolngists nnw conrendthar intrauterine irradiarion and childhoodleukemia are causally relared. alrhough rhesame relarionship wirh respecr ro solid(UIDQes remains questionable. However, hecomends there is no associadon betweenchildhood leukemia and paternal precon­ceprional irradiation and states that a causalinterpretation of this association has beenabandoned by scienrific experts.

Toxicity of Second-HandSmoke

Bascom er al. (p. 1026) show thar acureexposure to siclesrream tobacco smoke iscapable of alrering clearance of foreignmarerial inhaled through the nose, reducingthe normal clearance fate of nasal mucous.However. rhere was a high degree of vari­ability among human subjects exposed tocigaretre smoke for one hour in inhalationchambers, tesulring in 6/12 subjecrsexhibiring a fasrer rare of clearance, 3/12showing no change after exposure. and3/12 displaying subsranrial decreases inclearing rates. In two subjects the toxiceffects persisted for rwo hours afi:er smokeexposure. More studies are needed toexplain the basis for the extreme biologicvariability and ro advance knowledge of rheparhogenesis of the chronic effects of envi­ronmemal robacco smoke.

Iodine in the Space Capsule

Astronauts experiencing extended spacetravel will use iodine ro disinfect rheirdrinking warer. There is paten rial foriodine toxicity. and the levels must bemonitored to ensure safety as well as effica­cy of rhe disinfectanr. Zareba er al. (p.1032) examined rhe urility of hair. saliva.and urine as sources for biological monirorsof iodine exposure. They found that hairwas unsuitable as a medium for monitor­ing, saliva was a good possibility because ircan be collected noninvasively, but urinelevels of iodine adjusted ro creatinine werethe most useful media for biological moni­toring of iodine in astronauts.

Lead in Mexican Children

Children living in Mexico Ciry exhibitblood lead levels ranging up ro 31 ~g/dl,

with 44% exceeding 10 ~g1dl, levels knownto cause developmental neurotoxicity.Romieu er al. (p. 1036) looked ar 200 chil­dren younger than 5 years old and deter­mined that lead-conraminated pottery andlead in dirt from children's hands, alongwirh rhe use of leaded gasoline, were themajor sources of lead exposure. Theauthors recommend education and infor­mation programs to reduce the use of lead­comaminated cookware and ro reinforcethe use of unleaded gasoline.

Accurate RadonMeasurements

Weinberg (p. 1042) reports that particulateindoor air pollution can affect rhe accuracyof radon measurements. The amount ofradon that has accrued can be measured byexamining decay products deposited onglass objects thar were continually presenrin occupant's homes. Uncertainties thatarise about such measurements can distortinferences from epidemiological srudies.such as the risk of lung cancer from radonexposure nr potenrial synergism berweenradon exposure and cigarette smoking.More methodological work is needed, butin the meantime, houses with excessive riskof radon exposure could be identified andremediation started.

Chelation for Toxic Metals

A Commentary by Goyer on chelariontherapies for toxic metals (p. 988) remindsus rhat there there is an incomplere under­standing of chelarion therapy, and its effec­tiveness is unproven. In a related MeetingRepon (p. 1048). Goyer et al. summarizethe results from a conference held at theNIEHS on rhe role of chelating agents forthe prevention, intervention, and uearmemof exposures to roxic metals. Lead chelarionusing EDTA, succi mer. and o-penicil­lamine are discussed, as are copies coveringchelation rherapy for mercury, cadmium,copper, and the radioacrive actinide ele­ments. Some of the research recommenda­rions include determinarion of optimalroures of administtarion for chelatingagents. poremial advantages for rhe simul­taneous administrarion of multiple chelar­ing agems, and designs for novel method­ological and experimental approaches rostudying lhe potenrial side effects associaredwith chelation.

980 Volume 103, Number 11, November 1995. Environmental Health Perspectives

NIEHS Superfund Basic ResearchWorld Wide Web Page

URL: http://www.niehs.nih.gov/sbrp/home.htm

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forced through legislarion or rhrough the humanirarian dispositionof a few enlightened individuals like Roberr Owen. Perhaps this isrhe lesson of history.

The systematic study of industrial medicine also began in GreatBritain during the indusrrial revolurion. Charles Turner Thackrah(1795-1833) was a physician who, in 1831, published a bookcalled The Effiro ofthe Principal Arts, Trades and Professions, and ofCivic States and Habits ofLiving, on Health and Longevity, withSuggestions fOr the Removal ofMany of the Agents which ProduceDisease and Shorten the Duration ofLift, a title that indicates thelove of scientists for lengthy titles has not changed, but whichcould have come straight from the pages of Environmental HealthPerspectives. This book was extremely important in stimulating fac­rory and healrh legislarion that mitigared some of rhe worsr featuresof the industrial revolurion. Among the mosr impotlant issues dis­cussed by Thackrah were those concerned with chronic lead poi­soning among house painters and potrers making glazed ware.Thackrah made specific recommendations for rhe elimination oflead poisoning from the glazing and pottery industry. However, theissue has not gone away in spite of the intervening 164 yearsbetween then and now. In this issue of EHP, Romieu et al. (p.1036) document contaminated pottery as a source of lead in chil­dren from Mexico Ciry.

While many have contributed to the foundarions of environ­mental health, there seems little doubr that rhe most valid claim toparenthood is that of Ramazzini. Ramazzini was the firsr physicianro systematically examine the effects of workplace on humanhealth, and his book De Morbis Artificum, published in 1700 (4),was the first treatise on the subject.

De Morbis Artificum is delightful to read. Considering rhe srateof medical knowledge ar rhe beginning of the 18rh century, theinsighr of Ramazzini is truly amazing. Some of his comments

Editorial

reflect not only rhe srate of medical understanding of the day butalso reflect some of his own personal beliefs. His eurocentriciry,normal for the time, is amusing, such as the comment found in thepreface of the book: "How much the mechanical arts have con­tribured to the enjoyment ofa more civilised life, anyone can calcu­late by observing what a vast difference there is between Europeansand Americans or the other barbarous races of the New World." Iwas particularly impressed by his insight into the pains and Stressesof being a scientific editor, which I gleaned by combining insightsfrom several sections of his book. The relevant chapters are"Diseases of Scribes and Notaries," "Diseases of Learned Men,"and a little from the chapter "Diseases of Cleaners of Privies andCesspits." Ramazzini also noted that scribes and notaries "wereusually slaves or freedmen," to which I add, with only a slighttouch of self-piry, might also account for the origins of scientificeditors. The aggravations of being an editor are summed up thus:"The diseases brought on by sitting continually are easily under­stood; they are obstructions of the viscera, e.g., the liver and thespleen, indigestion in the stomache, numbness of the legs, a consid­erable hindrance of the circulation of the blood, and an unhealthyhabit."

Gary E. R. HookEditor-in-Chief

REFERENCES

1. Paracelsus. Von dec Bergsuchr und anderen Bergkrankheiten. 1567.2. Agricola G. De Re M«a1lica. 1556.3. Humer D. The diseases of occupations, 4th ed. The English Universities

Press Ltd., 1969, p. 28.4. Ramamni, B. De Motbis Arrificum Diarriba. 1700.

Environmental Health Perspectives. Volume 103, Number 11, November 1995 983

Correspo.;;;...;;n...::.:.d....;:::;cen:....;;.c=..;e~ _

Science Funding(Editorj Note Following is a "printofa kt­ter sent to Donna Shalala, secretary of theDepartment ofHealth and Human Services,on 9 June 1995.)The budget now under consideration in theCongress for the National Institute ofEnvironmental Health Sciences wouldindefensibly threaten environmental healthprotection for America. For millions ofAmericans the environment is a majordeterminant of their health, and for thequarter-century that it has existed, theNational Institute ofEnvironmental HealthSciences has been the first line of defenseagainst these threats. Its record of success isunsurpassed among the National Institutesof Health. Now, as an increasing numberof disorders ranging from premature birthsro a wide variety of cancers, appear to havean environmental cause or component, afully funded NIEHS is essential.

NIEHS is unique among the institutes.By focusing its research efforts on thehealth impacts of environmental exposures,ranging from air pollution ro food addi­tives, NIEHS provides cross-cutting sup­port ro the other instirutes and a wide rangeof regulatoty agencies. There is no questionthat NIEHS-supported research hasimproved the quality oflife in response to adeep and abiding commitment by the pub­lic to environmental protection. Moreover,NIEHS programs have been instrumentalin making the United States the world'sleader in biomedical research, providing afoundation for the nation's expanding,highly profitable biotechnology industry.One of the more prominent NIEHSresearchers is a Nobel laureate, and mOSt

are world leaders in their field of inquiry.NIEHS-sponsored research is opening

the door to an understanding of the molec­ular and cellular-level mechanisms bywhich diseases and disorders are caused,making it possible to develop methods ofptevention and treatment for all illnesses,not just those with environmental causes.For example. within the last year alone,NIEHS researchers have discovered rhegene that causes breast cancer and anotherthat is associated with metastasis of cancerof the prostate.

WHAT'S YOUR PERSPECI1VE?

EHP welcomes letters abour articles ortopics appearing in the journal. Send let­ters ro: Editor-in-Chief, EnvironmentalHealth Perspective~ National Institute ofEnvironmental Health Sciences, PO Box12233, Research Triangle Park, NC,27709 USA.

Most importanrly, literally everyAmerican, especially our children and elder­ly, is roday safer and healthier because ofresearch supported by the National Insrituteof Environmental Health Sciences.Collectively, this reduction in the nation'sburden of illness due ro environmentalexposures has been cost effective by virtuallyany measure. Consider, for example, that:

• NIEHS research on the effects of leadon children's nervous systems caused it tobe removed from gasoline, safeguardingthe intelligence of American children.Other research associating lead with elevat­ed blood pressure, and therefore increasedrisk of heart artack and stroke in men, wasinstrumemal in eliminating this ubiquitousmetal from a variety of othet uses, rangingfrom plumbing solder to paints.

• NIEHS studies of pesticides-aldrin,dieldrin, and heptachlor, ro name butthree-helped demonsttate the dangers ofpesticides generally, supporting tegulationsthat have made food safer for consumetsand work less threatening for farm families.

• Research on air pollutants such asowne, sulfur dioxide, and carbon monoxidedemonstrating, for example, that particulatepollution is associated with roughly 60,000deaths per year, has laid the groundwork forthe national effort to lower the levels ofthese compounds. There can be little doubtthat tens of millions of Americans arehealthier because of these efforts. Othersare, quite literally, alive because of them.

Due to its expertise, NIEHS has beenassigned responsibility for programs fund­ed through other laws. For example, theinstitute has provided health and safetytraining and education to more than100,000 workers involved in the cleanupof hazardous waste sites or responses (Q

toxic chemical releases.The list of NIEHS successes could con­

tinue for pages, but despite these achieve­ments much remains to be done.Environmental agents, including not only airand water pollutants, but food contami­nants, tobacco smoke, and wotkplace chemi­cals, are implicated as a cause or componentin a wide range of diseasesThese includecancers of the brain, breast, pancreas,prostate, testicle, and a variety of otherorgans. Some serious diseases in which envi­ronmental exposures are implicated areincreasing at an alarming rate. These include,for example, asthma, especially in children.Environmental causes have been implicatedin all these, as well as Alzheimet andParkinson diseases, premarure births, sponta­neous abortions, liver and kidney disordets,as well as a wide range ofother illnesses.

The proposed budget threatens bothcurrent and future research at a time when

both the Congress and rhe administrationwill require more and better informationbecause of legislation designed ro compelthe application of science through riskassessments and cost-benefit analysis.Adopting that budget will cripple the effortto assure that sound science underliesnational regulatory decisions. It also willrequire drastic, immediate revisions thatwill threaten the nation's ability ro main­tain a viable biomedical research establish­ment which, in rum, will reduce our abilityto cure disease and, especially, ptevent it.

We urge you to share our views withMembers of Congtess and ro spare noeffort to assure that the National Instituteof Environmental Health Sciences is fund­ed at least to the level propsed by the presi­dent. Further, we urge you and your col­leagues in the administration to speak out,and vigorously defend not only the budgetof the National Institute of EnvironmentalHealth Sciences, bur those of the otherinstitutes as well.

The National Advisory EnvironmentalHealth Sciences Council

Norma C. BarfieldAnn Arbor, Michigan

Patricia A. BulBerUniversiry of California

Berkeley, California

Doyle G. GrahamDuke University Medical Center

Durham, North Carolina

Bernadette Gray-LittleUniversity of North CarolinaChapd Hill, North Carolina

Phylis GreenbergerThe Society for the Advancement of

Women's Health ResearchWashington, DC

Philip S. GuzelianUniversity ofColoradoHealth Sciences Center

Denver, Colorado

Maureen HendersonFred Hutchinson Cancer

Research CenrerSeattle, Washington

Rogene HendersonLovdace Inhalarion Toxicology

Research InstitureAlbuquerque, New Mexico

LoveUJonesThe University of Texas

Houston, Texas

Michael LiebermanBaylor College of Medicine

Housron, Texas

Curtis A. MooreMcLean, Virginia

984 Volume 103, Number 11, November 1995. Environmental Health Perspectives

Rafael MoureUniversity of Lowell

Lowell, MassachusettS

Thomas E. NorrisSchool of Medicine

University of North DakoraGrand Fotks, North Dakora

Cecil B. PikerrSchering Plough Research Insrirure

Kenilworth, New Jersey

Macolm C. PikeUniversity of Southern California

Los Angeles, California

George ProvenzanoUniversity of Maryland

Baltimote, Maryland

Donald J. ReedOrgeon Stare University

Corvallis, Oregon

Mary VoreCollege of Medicine

University of KentuckyLexington, Kentucky

I. Bernard WeinsteinColumbia-Presbyterian Cancer Center

New York, New York

Inflammation: More Than OneExplanation

I read with interest the EHP supplementon oxygen radicals and lung injury (vol.102, supplement 10). I would like totake this opportunity to comment aboutthis supplement and raise a key issueconcerning the major concepts regardingthe mechanisms of cellular injury ininflammatory diseases.

AI. an active investigator in this fieldof research, I cannot fully understandwhy there was no mention in the supple­ment about the basic undetstanding thatcellular damage in inflammation is multi­factorial. The nonexpert reader of thissupplement might receive an erroneousimpression that oxygen radicals, per se,are rhe exclusive toxic agonists thatinduce cellular injury. Many in this fieldshare the view that cellular damage ininflammatory diseases might be causedby a "cootdinated cross-talk" among oxi­dants, membrane-damaging agents, pro­teinases, atachidonic acid metabolites,phospholipases, cationic proteins, andcyrokines. All these agents are likely to bepresent in sites of infection and inflam­mation. But sadly, none of the publica­tions elaborating on this multifactorialview ate quoted in modern textbooks orin symposia on inflammation andinflammatory diseases. Instead, the liteta­tute is filled with publications that insiston a single agonist, be it an oxidant, a

protease, a cytokine, etc., in expetimentalmodels. No attempt ro integrate the vari­ous agonists into the full picture is made.

Sevetal of Out publications (1-1) dealwith synergistic interactions among mul­tiple proinflammatory agonists in cellularinjury during inflammation. I believethat this issue is important, timely, andmight conttibute to an understanding ofhow drugs, chemicals, and xenobioticsfunction in vivo.

Isaac GinsburgHadassah School of Dental Medicine

Hebrew UniversityJerusalem

REFERENCES

1. Ginsburg 1, Kohen R. Synergistic effectsamong oxidants, membrane-damaging agents,fatty acids, proteinases, and xenobiotics:killing of epithelial cells and release of arachi­donic acid. Inflammarion 19:101-118 (1995)

2. Ginsburg I, Kohen R, Ligumsky M. Ethanolsynergizes with hydrogen peroxide, peroxylradical, and trypsin to kill epithelial cells inculture. Free Rad Bioi Med 16:263-269(1994).

3. Ginsburg I. Can hemolytic streptococci beconsidered "forefathers" of modern phago­cytes? Comp Biochem Physiol C109,147-158 (1994).

4. Ginsburg I, Mi", RS, Gibbs DF, Varani J,Kohen R. Killing of endothelial cells andrelease of arachidonic acid: synergistic effectsamong hydrogen peroxide, membrane-dam­aging agems, cationic substances, and pro­teinases and their modulation by inhibitors.Inflammalion 17:295-319 (1993).

5. Ginsburg I, Misgav R, Pinson A, Varani j,Ward PA. Kohen R. Synergism among oxi­dants, proreinases, phospholipases, microbialhemolysins, cationic proteins. and cytokines.Inflammarion 16:519-538 (1992).

6. Ginsburg I, Gibbs DF, Schuger L, JohnsonKj, Ryan US. Ward PA, Varani j. Vascularendothelial cell killing by combinations ofmembrane-active agents and hydrogen perox­ide. Free Rad Bioi Med 7:369-376 (1969).

7. Varani j, Ginsburg I, Schuger L, Gibbs OF,BrombergJ,Johnson KJ, Ryan US, Ward PA.Endothelial cell killing by neutrophils: syner­gistic interaction of oxygen products and pro­reases. Am J Pathol 135:435-438 (1989).

ResponseWe appreciate rhe interest shown by Dr.Ginsburg in our recent conference proceed­ings (EHP 102, supplement 10). As sratedin the preface of those proceedings, TheOxygen Radicals and Lung InjuryConference was the first of its kind dedicat­ed to pulmonary science. Therefore, in thisconference, the primary attempt was rofocus on oxygen radicals and their involve­ment in roxic insults and the ensuing patho­physiological processes in the lung. We did

Correspondence

not ignore the importance of multifacrorialrelationships of other cellular reactions andproducts involved in cellular damage andinjuty. In fact, these issues were addressed inthe presentations of Ward (1), Holian et al.(2), Repine (3), Torphy et al. (4), andDemers and Kuhn (5). The complex net­work of micromolecular reactions have notbeen fully defined ro understand the coordi­nation, modulation, and integration of cel­lular functions. In many pulmonary diseases(e.g., cancer, emphysema, pneumoconiosis)in which oxygen radicals are implicated, thedisease becomes evident only after severalyears. Subtle damage or changes to biomole­cules and their relationships to the coordi­nation and interactions of oxygen radicalgeneration and degradation are importantissues to be dealt with in greater detail rounderstand the synergistic concepts of lungdieases. We hope that future conferenceswill address these and other issues.

V. VallythanV. Castranova

K. WeberNarional Institute of Occupational

Safety and HealrhMorgantown, West Virginia

REFERENCES

I. Ward PA. Oxygen radicals, cytokines. adhe~

sion molecules, and lung injury. EnvironHealth Perspecl 102(SuppllO),13--16 (1994).

2. Holian A, Kelley K, Hamilron RF Jr.Mechanisms associated with human alveolarmacrophage slimulation by parriculates.Environ Health Perspect I02(Suppl10):69-74 (1994).

3. Repine jE. Interleukin-I-mediated acute lunginjury and tolerance co oxidative injury.Environ Healrh Perspecr 102(Suppl 10):75-78 (1994).

4. Torphy TJ, Barnette MS, Hay DWP,Underwood DC. Phophodiesterase IVinhibitors as therapy for eosinophil-inducedlung injury in asthma. Enviton HealthPerspecr 102(Suppl 10):79--84 (1994).

5. Demers LM, Kuhn DC. Influence of mineraldusts on metabolism of arachidonic acid byalveolar macrophage. Environ Health Perspect102(SuppI10):97-100 (1994).

MTBE: Not CarcinogenicSubsequent ro publicarion of EHP'stimely article on the toxicological poten­tial of methyl-tert-buryl ether (MTBE;vol. 103, pp. 666-670), the long-await­ed srudy from the Ramazzini Foun­dation of Oncology and EnvironmentalSciences appeared in print (1). This wasa landmark publication because formonths we in the scientific communityhad been advised that the data predicreddire health hazards for humans exposed

Environmental Health Perspectives. Volume 103, Number 11, November 1995 985

Correspondence

to MTBE. According to the EHP aniele,several scientisrs held the hope thar the"Maltoni' work would clarifY questionsabout MTBE's carcinogenic potential.

Despite rhe enthusiasm ofsome scien­tisrs for Belpoggi's resulrs, the most curso­ry examination of the paper reveals criticalissues that show the data have been gross­ly overinterpreted. Rather thao predictinga health hazard, the dara indicate that rarstoletate enormous daily oral doses ofMTBE without exhibiting evidence ofeither tumor or nontumor pathology.

Leydig ceO trmtON in high-dose millerats. According to Belpoggi et aI., theadministration of MTBE as ao olive oilgavage to male rars (1.0 glkg, 4 days perweek) was associated with a significantincrease in the incidence of Leydig celltumors. But examination of the totalinformation in the paper shows that thereported effect cannot be attributed toMTBE. The apparent association was dueto a survival differential between controlaod dosed aoimals. Male rars administeredthe highest dose of MTBE survived longerthan the control group. It is well knownthat Leydig cell tumor incidence is agerelated. The longer a rat survives, the morelikely it is to have Leydig cell tumors.Claiming this survival-related effect to beindicative of a human health hazardstrains the bounds of scientific logic. Thisis particularly true since Leydig cell neo­plasms are most likely unique to rats aodappear to have no predictive utiliry forhumao carcinogenic responses (2).

LymphomilanJ leukemia (combined)in femllie rats. Belpoggi et al. reportedthat MTBE increased the incidence oflymphomas and leukemias (combined)in female rats. Since no mention wasmade of the incidences of these neo­plasms individually, one can only assumethat neither was significantly elevated.

The scientific validiry of combininglymphomas aod leukemias for statisticalpurposes is highly questionable. ANational Toxicology Program workingcommittee reviewed scientific guidelinesand criteria for the combination of neo­plasms during the interpretation ofrodent carcinogenesis studies (3).According to rhar group of experiencedpathologisrs, combining certain tumorsfor sratistical purposes is appropriate aodmight afford enhaoced insighrs into rhebiological effecrs of the test chemical. Inother cases, however, combinations areunjustifiable and can lead to overesti­mates ofcarcinogenic potential.

According to the NTP panel, it isreasonable to combine different rypes ofleukemias and to combine different

rypes of lymphomas. But it is not appro­priare ro combine leukemias with lym­phomas. Treatment-associated increasesin the incidence of one or the other ofthese tumors of diverse cellular originmay be suggestive of an oncogenic effect.But, since the incidence of neither wassignificantly and independently elevated,the authors' interpretation of this por­tion of the study represents an overesri­mation of carcinogenic potential.

The science of carcinogenic hazardidentification and tisk assessment hasprogressed well beyond the days of sim­ply counting tumors and rhen makinggrand leaps ro unfounded and insup­porrable conclusions. As we expand ourunderstanding of chemical carcinogene­sis and the predictive validity of ourexperimental models, we must employcritical and scientific thought processesthat incorporate the total knowledgeabout the chemical. The total of perti­nent knowledge about the carcinogeniceffects of MTBE in laboratory animalsshows that:

• The oral administration of up to Ig/kg of MTBE four days a week pro­duced neither neoplastic nor non-neo­plastic chaoges in male and female rats,

• The chronic inhalational adminis­tration of grossly toxic concentrations ofMTBE produced an increased incidenceof hepatocellular adenomas in female(but not male) mice and an increasedincidence of tenal tubular cell adenomasand carcinomas (combined) in male (butnor female) rats,

• Neither MTBE nor its metabolite,tertiary buryl alcohol, possess genotoxicpotential in eirher in vitro or in vivomodels,

• A potential metabolite of MTBE,formaldehyde, possesses equivocal geno­toxic potential in mammaliao models, but

·Even when administered ar inhala­tional doses thar are lerhal to rats andcytotoxic to mice, MTBE possesses nogenotoxic potential in in vivo mam­malian models.

These scientific facts lead to the con­clusions that supramaximal inhalarionaldoses of MTBE cause increased inci­dences of liver neoplasms in female miceand renal neoplasms in male rats. Butsince MTBE and its metabolites possessno genotoxic potential, the proliferativechanges in response to toxic doses aremediated through nongenotoxic mecha­nisms that tequire cytotoxicity to precip­itate prolifetation. Because of the intenseodor (and taste) of MTBE, humans willnot colerate either air or water concemra­tions sufficient to produce the cytotoxic

precursors required to promote cellularproliferation. In short, the carcinogenichazard associated with MTBE has beenidentified and defined. The human risk,however, appears to be so small rhat it isessentially nonexistent.

John H. MennearSchool of Pharmacy

Campbell UniversityBuies Creek, North Carolina

REFERENCES

I. Belpoggi F, Soffrirti M, Maltoni C. Methyl­tertiary-butyl ethet (MTBE)-a gasoline addi­tive-causes testicular and lympho-haematO­poietic cancers in rous. Toxicollnd Health 11:119-149 (1995).

2. Prentice DE. Meikle AW. A review of drug­induced Leydig cell hyperplasia and neoplasiain the rat and some comparisons with man.Hum Exp ToxicoI14:562-572 (1995).

3. McConnell EE, Solleveld HA, Swenberg JA,Boorman GA. Guidelines for combining neo­plasms for evaluation of rodent carcinogenesisstudies. JNad Cancer Inst 76:283-289 (1986).

Clarification: ChemicalSyngergism

In a recent EHP Forum article ("Menacein the Mix," vol. 103, pp. 792-793)concerning Dr. Mohammed Abou­Donia's work related to the Gulf Warsyndrome, I am quored as saying first"Irs a plausible hyporhesis that syner­gism occurred" and second "That's notto say [the hyporhesis] is an appropriatelead for furrher investigation." Clearlythese two sratements are contradictoty,and rhe second rends ro place me in aadversarial position relative to Abou­Donia. All of this arose from a back­ground discussion of synergism, of thenature of hyporheses and how scienceproceeds, not from a specific discussionof Abou-Donia's work, since rhe larrerwas not available to me.

My position, based on the prelimi­nary statements that have appeared con­cerning this work, is that it is interesting,that it provides a plausible hypothesis,and that it does indeed provide a basisfor further studies. I hope, and believe,that nothing I said in the interview wascritical of the authors of this work anddid not go beyond what I would havediscussed with them in a friendly discus­sion between fellow toxicologists.

Ernest HodgsonDepartment ofToxicology

Norrh Carolina State UniversityRaleigh, North Carolina

986 Volume 103, Number 11, Novenber 1995· Environmental Health Perspectives

Finnish Institute of Occupation Health sponsors an

International Symposium onWork in the Information Society

20-22 May 1996Marina Congress Center, Helsinki, Finland

Theme ITechnology development il)O¥l_~1

occupational health and sa• workplace design• ergonomics• optimizing human-technolog

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Theme IIOccupational health and s

aspects in the information• job contents• work organizations• working times• support to psychological

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Additional Information:

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Tel: 358 0 47471Fax: 358 0 4747548

e-mail: sleh@occuphealth.fi

Commentary

Chelation of Toxic Metals: Current InterestsRobert A. Goyer

National Institute of Environmental Health Sciences, Research Triangle Park. NC 27709 USA

Chelation thetapy has long been tegatded asa suitable apptoach to the therapeutic andeven ptophylactic removal of potentiallytoxic metals ftom body tissues. And thetehave been apparent successes in some areas,but there are also needs for a better under­sranding of the underlying pharmacologyaod for the development of safer and moreeffecrive agents.

There are currently three areas of inter­est in the clinical use of chelating drugs:treatment of heavy metal toxicity, removalof metals accumulated in body tissuesbecause of genetic disorders, and chelariontherapy of degenerative diseases of theblood vessels. An NIEHS symposiumfocused primarily on mechanisms, effective­ness, and potential adverse effects of tradi­rional as well as new chelating agents (seeMeeting Report in this issue). While mostof the presentations concerned treatment oflow-level lead exposures, the conferencetopics and discussions extended into thecurrent status of chelation therapy for otherdisorders. There were also discussions ofrarionales for designing appropriate chelat­ing agents. Experimental results of the labo­rarory testing of ptomising new drugs sug­gest thar the development of more specificand effective agents is possible. None of thenew drugs have been subjecred to humanclinical trials.

Much of the current interest in chelat­ing agents srems ftom concerns abour thepossible beneficial effects of removal oftoxic metals in people wirh low-level expo­sures without overt symptoms of toxicity.This interesr is ptompted by emerging evi­dence that toxic effecrs from exposures tolead, cadmium, and mercury may occur atlevels previously thought to be harmless andar levels that do not ptoduce overt clinicalsymptoms. It is now well established thatlow-level exposures to lead in early child­hood may impair cognitive and behavioraldevelopment (1), while lifetime accumula­tions of cadmium in liver and kidney areassociated with renal tubular dysfunctionand hypercalciuria in larer life (2). Morerecenrly, there have been assertions thatmercury vapor released from dental amal­gams might be responsible for a spectrumof chtonic health ptoblems (3,4). Althoughit may be debated as to what the lowest lev­els for concern might be for each of thesemetals, it is clear that the margin betweenthe levels of exposure for petsons living inthe industrialized narions of the world and

levels of exposure currently recognized asptoducing the lowest adverse effect levels issmall. While effons to reduce exposure tothese metals are being implemented, thereare large populations of children and adultsthat mighr have exposures thar exceed rec­ommended levels or have some slight,though measurable, adverse effect.

In spite of the substanrial decline inblood lead levels (BPb) for children in theUnired Stares over the lasr 10 years asdetermined by the mosr recent NationalHealth and Nutrition Evaluation Survey,35% of non-Hispanic, black children haveBPb 2:10 fIg/dl, in contrast to an overallaverage of abour 4% (5). It may be arguedthat the best treatment for the overexposedchildren is removal from porential sourcesof exposure, but it is unlikely rhat rhemajor risk factors, homes containing lead­based paint, can be correcred in rhe nearfurure. From this perspecrive chelationbecomes an appealing alternarive.However, there are a number of unan­swered questions regarding rhe effective­ness of available chelating agents. There iscurrently no conclusive evidence thatreduction of blood lead levels by chelationwill reverse neurological effects already pre­sent. Also, historically, the drug of choicefor treatment of lead poisoning isCaNa2EDTA, which is administered byinfusion, is relatively nonspecific and pto­motes loss of essential cations. Therefore,the use of EDTA has been reserved forinstances ofclinical lead toxicity. However,with the recent availabiliry of DMSA (suc­cimer), an orally administered drug, theenthusiasm for therapy of children withlow-level exposure to lead is gtowing (6).But this alternative drug only has FDAapproval for reduction of BPb levels >45fIg/dl.

The adverse effects of excess cadmiumexposure become evident in older adulrpopulations: renal rubular dysfunction andhypercalciuria, which is a factor in thedevelopment of osteoporosis (7). Dailyinrake of cadmium from food in mostindustrialized countries is abour 10-50fig/day; the upper limit recommended bythe U.S. EPA Integrated Risk InformationSystem is 70 fig day, similar to the permis­sible weekly intake recommendation of theJoint Food and Agriculture Organi­zation/World Health Otganization ExpertCommittee (8). Renal tubular dysfunctionattributable to excess cadmium exposure

affects large populations of adults in Japan,The Netherlands, and Belgium (2,9).Because of the long retention time in soft­tissue (half-life of 30 yeats), the tenal effectsare not reversible within 10 or 15 years orlonger, and may be progtessive. It seemsappropriate therefore to look to a chelatingagent to reduce the problem, at least insevere cases, but none is available at present.

Concern about mercury exposure islargely from consumption of fish contain­ing methylmercury, which may be a hazardto the developing fetus. The EPA and FDAhave monitored fish consumption andexposures to high-risk popularions in theUnited States. Again, thete is only a smallmargin of safety for large groups of chil­dren, and, as discussed at the conference,methylmercury is probably not chelatable.A second exposure to mercury for personsin the general population is elemental met­cury or mercury vapor from denral amal­gams. Although mercury-containing amal­gams have been used in dentistry for morethan 100 years without demonstratedadverse effects, it has how been shown thatmercury in· tissues can be related to thenumber of mercury-containing dental fill­ings and that there is a relationship betweennumbers of metcury amalgams and mercurycontent of tissues, including the nervoussystem, of newborn infants (JO). Thechelating agents DMSA and DMPS canenhance urinary excretion of elementalmercury, which, in turn, can be related tothe number of mercury-containing dentalfillings. While there is no substantiatedhealth effect from tissue levels of mercuryattributable to dental amalgams, it is allegedthat a number of nonspecific, chronic con­ditions can be ameliorated by removal ofthe amalgams or by chelation. None of thishas been supported by confirmed peer­reviewed research, but it has amacted thepublic interest in removal of amalgam fill­ings and chelation therapy for removal ofmercury.

Chelation therapy has long been theonly method for teducing body burdens ofmetals resulting from genetic disorders ofmetal metabolism such as copper accumula­tion in Wilson's disease, cystine crystal for­mation in cystinuria, and removal of tissueiron in hemochromatosis. For these disor-

Address correspondence to R.A. Goyer, NIEHS,PO Box 12233, Research Triangle Park, NC 27709USA.

988 Volume 103, Number 11, November 1995 • Environmental Health Perspectives

Commentary' Chelation of toxic metals

ders the rationale for chelation therapy issupported to some degree by clinical experi­ence and there are, at present. no alterna­tives. However, there is an expanding inter­est in chelation therapy for the treatment ofdegenerative vascular disease due to arte­riosclerosis. The initial assumption was thatchelation with EDTA worked by chelatingcalcium from atherosclerotic plaques andhence improved blood flow in narrowedvessels. While this hypothesis has lost favor,practitoners of chelation therapy believethat EDTA works by chelating iron andcopper, reducing the generation offree radi­cals and subsequent lipid peroxidation(11,12). Literature aimed at the lay readerand widely available in health food storesfavors chelation therapy for treatment of"narrowing of the arteries" rather thanestablished techniques of angioplasty andbypass surgery (13,14). The effectiveness ofchelation therapy for treatment of peripher­al vascular disease is being debated (15);double-blind, randomized srudies do notsupport clinical efficacy (16,17). On theother hand, one might see the appeal of therelacively low cost. noninvasive nature ofthis approach. Lay literarure provides con­siderable anecdotal support for effectivenessand even endorsements by some physicians.

All of these interests and needs arguefor increased research effeorrs to provide abetter understanding of what chelationtherapy does and does not do and to iden­tify its risks. In most cases it is not difficultto demonstrate increased excretion of themetal, bur in few instances has the clinicalefficacy of the treatment been demonstrat­ed with any scientific rigor (18). Althoughthere may be evidence for the abiliry of aparticular agent to enhance excretion of ametal in question, there is a paucity of evi­dence that any of the uses of chelationtherapy reverses toxiciry at the cellular levelor ptevents progression of the pathology

produced by the accumulated metal.It is apparent that there are serious defi­

ciencies in the understanding and effective­ness of chelating agents for the removal ofroxic metals and treatment of metal toxici­ties. There are many reasons for this stateof the science. There has not been suffi­cient basic research to elucidate the celleffects and mechanisms of action andeffects of chelating agents on the biokinet­ics of toxic metals. Investment in researchin these topics has lagged because of theview that need for chelation therapy is sec­ondary to reduction in exposure. Anmhermajor reason is the large costs associatedwith drug development for a small and spe­cialized market. The clinical testing of achelating agent involves identification of anappropriate cohorr, a random double-blinddesign that incorporates scientifically credi­ble measures of clinical outcome, and alarge financial outlay. Added to these diffi­culties is ethical acceptance of the use ofplacebos essential for the conduct of a dou­ble-blind study. These considerations donot foster confidence that the scientificallydesired ideal for these therapies will beimminent. However, awareness of the defi­ciencies of knowledge should be reason forcaution not [Q do harm and not to generatefalse expectations.

REFERENCES

I. CDC. Preveming lead poisoning in young chil­dren: a statement by the Centers for DieaseControl. Atianta,GA:Cenrers for DiseaseControl, 1991.

2. WHO. Cadmium. IPeS environmental healthcriteria J34. Geneva:World Health Organi­zation, 1992.

3. Skare I, Engqvisr A. Human exposure to mer­cury and silver released from dental amalgamrestorations. Arch Environ Health 49:384-394(1994).

4. Basu MK. Wilson HJ, Krishnan G. Mercury,;sk [<om teeth. Nature 349,109 (1991).

5. P;dde JL, B<ody DJ, Gumer EW, Kramer RA,Paschal DC, Flegal KM, Marte TD. Thedecline in blood lead levels in the UnitedStates. J Am Me<! Assoc 2n284-29 I (1994).

6. Mortensen ME. Succimer chelation: what isknown. J Ped;arr 125,233-234 (1994).

7. Goyer RA, Epstein S, Bharracharyya M, KorachKS, Pounds J. Environmental risk factors forosteoporosis. Environ Health Perspect102J90-394 (1994).

8. WHO. Forty.first report of the JointFAO/WHO Expert Committee on FoodAdditives. WHO technical report series 837.Geneva:Worid Health Organization, 1993;28-30.

9. Buchet JP, Lauwerys R, Rods H, et aI. Renaleffects of cadmium body burden of the generalpopularion. Lancet 336,699-702 (1990).

10. Drasch G, Schupp I, Hon H, Reinke R, Ro;de<G. Mercury burden of human fetal and infanttissues. Eur J Ped;arr 15%07-610 (1994).

11. Babu AN, Gomzalez·Penna H. Iron chdatingagents are not useful in treating atherosclerosis.Ann 1m Med 12U84-385 (1994).

12. Vom EE, Vreugdenhil G, M"x JJ. Iron­chelating agents in non·iron overload condi·tions. Ann 1m Med 120,490-499 (1994).

13. Walker M. The chelation way. Garden City,NY,Avel)' Publish;ng Gmup, 1990.

14. Brecher H, Brecher A. Forry something forever:a consumer's guide to chelation therapy.Herndon,VA:Health Savers Press, 1992.

15. Chappell LT, M;randa R, Hancke C,Frackelton JP, Carter JP. EDTA chelationtreatment for peripheral vascular disease. Ann1m Med 231 ,429-430 (1992).

16. Guldage< B, Jelnes R, Jorgensen SJ, N;elsen JS,Klaerke A, Mogensen K, Larsen KE, Reimer E,Holm J, Ottesen S. EDTA treatment of inter­mittent claudication-a double blind placebo·controlled study. J Int Med 23U61-267(1992).

17. van Rij AM, Solomon C, Packer SGK,Hopkins WG. Chelation therapy for intermit­tent claudication: a double blind, randomized,controlled trial. Circulation 90: 1194-1199(1994).

18. Kosnett MJ. Unanswered questions in metalchelation. Clin Toxico130,529-547 (1992).

American Occupational Health ConferenceAnnual Conference of The American Assocation of Occupational Health Nurses, Inc. &the American

College of Occupational and Environmental MedicineApril 26-May 3, 1996

San Antonio Convention CenterSan Antonio, Texas

For information:Nancy Kay Olson

Director of Conference & MeetingsAmerican Occupational Health Conference 55 W. Seegers Road

Arlington Heights, IL 60005

Environmental Health Perspectives. Volume 103, Number 11, November 1995 989

Environews\~ .

Waste is a terrible Ihing to min~ecycle.

Bumper slicker

Forum

Little people, big effects. The children of Belarus may bear the biggest brunt of adverse health effectsfrom the accident al Chernobyl.

Children of ChernobylIn the aftermath of the April 1986 explosionof the Chernobyl nuclear power planr in theUkraine, incidence rates of childhood can­cers, especially of the thyroid, have been dra­marically increasing. The United Staresagreed rhis past May to join wirh theUkraine to study the effecrs of radiarionexposure on childhood thytoid cancer.

The accident at Chernobyl is rhe onlyfull-scale meltdown of a graphire core in anuclear energy station that has ever occurred.Ir released radioactive material over parrs ofthe former Soviet Union, Eastern Europe,Scandinavia, and later, Western Europe.killing 31 and hospitalizing 300. Scientistspredicted that it would lead to an undeter­mined number of future cancer deaths ovet alarge area.

In particular, the independent nation ofBelarus, northwest of Ukraine, where morethan two million people were exposed totadiation from Chernobyl, has recordedsteadily increasing numbers of cancer inci­dences and congenital malformations and ill­nesses. "At first people did not want to linkthese medical problems with Chernobyl, andmany accused us of radiation phobia:Yevgeny Konoplya, director of theRadiobiology Institute of Belarus's Academyof Sciences and an expert on post-Chernobyleffecrs, told the Washingwn Post. "But nowthey know. All the problems they faced in

agasaki we face here. There was no place ashard hit by Chernobyl as Belarus."

In 1986, there were 2 cases of thyroidcancer in childsen under 14 in Belarus, burby 1994 there were 82 registered cases.According to the Washington Post article, atthe Borovlyani cancer insricu(e outsideMinsk, more than 50 children are now beingtreated for brain tumors, bone rumors, kid­ney tumors, and orner cancers.

Since the collapse of the Soviet Union,independent nations have lacked funding tosuppOrt such widespread public health prob­lems. Therefore, the United States has agreedto step in and help. The U.S. Department ofEnergy announced this past spring that itwill work with the government of Ukraine toestablish an international nuclear safety andenvironmental research cemer at Siavurichnear Chernobyl.

Efforts to establish the center are a resultof a collaboration between the State De­parrment, the DOE, the Nuclear RegulatOl)'Commission, and Ukrainian nuclear andenvironmental agencies and organizations."This action is a significant step towardestablishing a Center of Excellence toimprove the safety of nuclear energy genera­tion in Ukraine, and reduce the risks posedby Chernobyl reactor operation, Secretary ofEnergy Hazel R. O'Leary said in a pressrelease. "The center will also serve as a focalpoint for international environmental

research in the areas ofenvironmemal coma­minarion and site reswrarion." The DOEwill spend about $3 million over the nextrwo years to establish the cemer. These fundsare part of a $38 million international effortto clean up Chernobyl.

In addition to establishing the center, theDOE and the NRC plan to provide fundingfor the National Cancer Institute to leadstudies on the effects of radiation exposureon childhood thyroid cancer. Over the next15 years, the DOE and the NRC will pro­vide $1 million annually for researchers toregularly test about 70,000 childsen exposedto radiation from the accident. Theresearchers will compare their findings todata gathered from childsen in the weeks fol­lowing the accident. They hope to determinethe extent to which radioiodine, especiallyiodine-13l, causes thyroid cancer and therole of possible cofactors such as iodine defi­ciency, according to the DOE.

Health Effects of DOEIn one of those serendipitous evems thatsometimes lead to scientific breakthroughs,researchers attending a lecture late last yearby University of Florida biologist LouisGuilette on developmental problems in malealligators realized they were seeing similareffecrs in laboratory rars recently exposed to afungicide. The ensuing discussion spurredresearch that may illuminate how environ­mental agents act like hormones to distuptdevelopment and possibly cause cancers.

Guilette reported that the alligators hadbeen exposed to DDT, a hazardous pesticidethar he said acrs as an environmental estro­gen. Too much emogen, Guilette stated,resulted in an imbalance of andsogen in thealligators, causing developmental defects.William Kelce and L. Earl Gtay, biologisrs atthe EPA's Health Effects Research labora­tory, guessed, however, that DDT was reallyacting as an ami-androgen.

Kelce and Gray had just published apaper in the June 1994 issue of Toxicologyand Applied Pharmacology detailing how thefungicide vinclozolin demasculinized ratpups by altering the action of the male hor­mone testosterone. Vinclowlin blocked nor­mal hormonal function by binding to theandrogen receptor. The fungicide boundloosely enough that the receptor was not acti-

990 Volume 103, Number II, November 1995 • Environmental Health Perspectives

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EHPnet

The Immortality EnzymeTelomerase, an enzyme that gives some cellsa permanent stay of execution, appears toplaya role in lung cancer progression,according to a study in the June 25 issue ofrhe Journal of the National Cancer lmtitute.Jerry Shay and his colleagues at theUniversiry of Texas Southwestern MedicalCenter at Dallas and at the HiroshimaUniversiry School of Medicine found telom­erase acriviry in approximarely 80% of the136 primary lung cancer tissues they tested,versus only about 4% of 68 adjacent normalrissue samples. Of rhe 136 primary lung can­cer samples, all I I of rhe small cell lung can-

for hormonally acrive compounds. "Pasr reg­ulatory testing was insensitive to these kindsof problems," says Ke1ce. "We are only nowbeginning to appreciare whar tesrs need to beconducred."

Guilette also wonders about the effecrof an anti-androgen on females: "If ir mod­ifies the esrrogen-androgen rario inwomen, increasing their estrogen, it couldresult in increased breast cancer and likediseases." Kelce says he has idenrified 20other chemicals that have anti-androgeniceffects. Although he says he can'r releasethe list yet, he indicated thar none of themis currenrly banned.

In war and football, it's often said that the best defense is a good offense. This same philoso­phy is the basis for a World Wide Web site aimed at improving the environment throughpollution prevention. Enviro$en$e (URL:http://wasrenor.inel.gov:80/envirosensel), whichis maintained at the Idaho National Engineering Laboratory, is funded by the EPA and theStraregic Environmental Research and Development Program (SERDP), a joint effort of theDepartment of Defense, rhe Departmentof Energy, and the EPA that supportsenvironmental qualiry research, develop­ment, demonstration, and applicationsprograms.

Eight hyperlinks on the Enviro$en$ehomepage offer a vast array of informa­tion in caregories such as news andresources, pollution prevention programsfrom rhe local to the federal level, internarional programs, rechnical research and develop­ment, compliance and enforcement, and more.

For example, the news hyperlink connects users to information such as a PollutionPrevention Direcrory, several hodines and clearinghouses, rhe National Consortium forEnvironmental Education and Training's Environmental Education Link (a gopher site thatoffers access to reaching resources including instrucrional marerials, articles, darabases, andgrant information), and the National Pollution Prevention Center for Higher Education.

Federal laws, regularions, environmental acriviries, and presidential executive ordets, andboth srare and local pollurion prevention servers may be accessed through another hyper­link. The international resources hyperlink provides information on pollution preventionprograms around rhe world by connecring to organizations such as rhe U.S. Agency forInternational Development's Environmental Prevention Prorection Project, the MontrealProtocol (protecrion of ozone layer), the North American Free Trade Agreement, rheOrganizarion for Economic Cooperarion and Development, and rhe Unired NarionsEnvironment Program.

The technical research and development hyperlink provides access to case studies andfact sheets on EPA studies of commercial companies, as well as environmental researchbriefs, project summaries, and pollution prevention assessments. This link also connecrsto rhe EPA Office of Research and Development and a pollution prevention publicationsbibliography. .

Perhaps rhe most innovative element of the site is an interactive search function rhatallows users to query the Solvent Alternatives Guide (SAGE), rhe Hazardous SolventSubsrirution Data System (HSSDS), and the Department of Defense Pollution PreventionTechnical Library. SAGE is a logic-rree sysrem rhat evaluates a manufacturer's current oper­aring scenario and then identifies possible alternative surface-cleaning solvent chemistriesand processes that best suir the operating and material requirements. HSSDS is an on-linesystem of information on alternatives to hazardous solvents that contains product informa­tion, material safery dara sheers, and other relared informarion. Also available on this sire isaccess to the Department of Defense Ozone Depleting Chemical! Substance Information.

vated, however, and therefore could nor sig­nal rranscriprion of androgen-dependentgenes, which disrupted sexual development.Vinclozolin was the firsr chemical reportedro have an anti-androgenic effect.

The EPA investigarors and molecularbiologists from rhe Universiry of NorthCarolina at Chapel Hill began ro comparerheir dara with Guilette's and months laterinvited Guilette ro the EPA ro examine theresults. The team found that DDE, the pri­mary metabolire of DDT, shrunk sex organsin male rats by up ro 20% in four days. Andpregnant rats exposed ro DDE gave birth romale rats with female sexual characteristics.

Guilerre and the rest of the scientificworld were surprised by the resulrs, pub­lished in Nature on June 15. "There wasquite significant binding rhar helps explainwhat we saw in the a1ligarors," says Guilette."]'m rethinking the whole concept of hor­mone receptor specificiry. Jr's much morecomplex than we realized." Guilette notedthat because some minor isomers of DDTare clearly esrrogenic, DDT and its metabo­lites are now known ro affect both estrogenicand androgenic hormone acrion.

DDE's anti-androgenic effects may helpexplain recent adverse changes in male repro­ductive health, such as decreasing spermcounts in various parts of rhe world, andincreases in testicular cancer and cases ofabnormal development of rhe penis andtestis. The work also raises the quesrion ofhow chemicals can act simultaneously as ago­nists and antagonists for both estrogen andandrogen, says Kenneth Korach, an NIEHSresearcher who was involved in creating anestrogen knock-out mouse. ElizaberhWilson, a Universiry of North Carolina atChapel Hill investigaror working with Ke1ce,is researching whether the androgen receptorforms a heterodimer, binding both DDEand androgen. The dose response of DDEwould be critical in this case, she says.

Although DDT was banned in rheUnited States in 1973, DDT and its mera­bolites persist in rhe environment (it has ahalf-life of up ro 100 years), and it is srillused ro control malaria in some countriessuch as Mexico and Brazil, and in some areasofMrica.

The EPNUNC team repotted that theconcentration of DDE needed ro inhibitandrogen receptor transcriprional activiry incell culrure or to affect newborn rar pups isanalogous to levels found in orher instancesof DDT contaminarion including Guilette'sFlorida alligator eggs and in kidneys of srill­born babies in the United Srates in the mid­1960s, when DDT was still being used.

Scientifically, the srudy offers more ques­rions rhan answers. It raises the issue of theadequacy of resting manufactured chemicals

Environmental Health Perspectives. Volume 103, Number 11, November 1995 991

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What a WasteIt may seem unusual for U.S. scien­tists and medical researchers to lobbystrongly against a government pro­gram to clean up the contaminatedFernald nuclear plant in Ohio, butthat's exactly what's happening. TheFernald plant, which processed ura­nium for nuclear weapons from1951 to 1989, now has about10,000 rons of radioactive wastecontained in two special silos.Within this waste, however, is amedically priceless stockpile of radi­um as well as millions of dollarsworth of gold and other pteciousmetals. Sciemists are arguing that

this radium, which is scheduled to be dis­posed of starting in early 1996, may be criti­cal to saving the lives of cancer patients if aclinical trial that attempts to cure cancer witha radium-based monoclonal antibody is suc­cessful.

David Scheinberg, a medical oncologistat the Memorial Sloan Kettering CancerCenter, is enrolling patients in a clinical trialto test a new methodology that links a radi­um-based isotope, bismuth-213, to a mono­clonal antibody to target cancer cells. Thetreatment is being tested on 10-20 patientswho have acute myeloid leukemia (AML) orchronic myeloid leukemia (CML). In a pre­liminary experiment using a leukemia mousemodel, the bismuth-213 antibody treatmentled to remission of the diseases and longersurvival rates. If the phase I trial scheduledfor November is successful, it will be fol­lowed by a slightly larger study within a yearof the phase I results. If further clinical trialsshow positive results and the treatment isapproved by the FDA, it could potentially be

are other immortalization mechanisms.According to molecular epidemiologist CurtisHarris of the National Cancer Institute, amechanism that enabled cells to escape senes­cence would be one that bypasses the problemofshrinking telomeres, such as DNA recombi­nation, probably a vety inefficient mechanism.If drugs were developed to target telomerase,these alternate mechanisms of immonalizationmight come into play to allow tumor cells to

escape senescence, says Harris. Even in thosecells where telomerase inhibitors successfullyprevented immortalization, any remainingsupply of telomeric repeats would allow thecell to continue to divide for a finite period oftime, with possible adverse consequences tothe patient. In addition, other cells in the

body, such as stem cells and stomach~ cells, might be sensitive to telomerase~ inhibitors, leading to serious side

effects.

types oflung cancer diagnostic tests.Researchers are already searching for a

drug that inhibits telomerase, in hopes of Cut­ting short the lives of the most proliferativelung cancer cells. In the August 3I issue ofScience, researcher Calvin B. Harley of GeronCorporation and his colleagues at Cold SpringHarbor Laboratory repotted that they wereable to ptoduce teverse RNA that blocked theaction of telomerase and caused HeLa cells, anexperimental cancer cell line, to begin dyingafter 23-26 cell divisions. While Harleyemphasizes that a drug able ro mimic thiseffect may take years to find and develop, sucha drug could prevent the spread of cancerwithout harming normal cells. In an interviewwith the Associated Press, Shay said, "This isthe first laboratoty proof that inhibiting oftelomerase RNA will result in limiting celldivision. ... This is the most important nextstep in telomerase research."

In an earlier AP interview Shay pointedout that the existence of metastatic tumorslacking telomerase activity implies that there

tumors may indicate that they consist entirelyof mortal cells. A ptevious study, published inScience, found that benign fibroid tumors didnot have telomerase activity. According toShay's study, "If cancers that have mortal cellsexist, their growth might be self-limiting incontrast to those that consist of immonal cells,"a possible reason why SCLCs are the most diffi­cult lung cancers ro treat. This distinctionbetween cell populations with telomerase activi­ty and those without it may serve as the basisfor tests to predict the cells' capacity for contin­ued proliferation and, therefore, the disease'sseverity. Te10merase activity might even befound in cells obtained from a patient's lungwash, a procedure Shay used in his study andone which is already commonly used for other

Solid gold silos? Two containers at the Fernald nuclear plant, slated for clean­up, hold medically priceless amounts of radium.

cers (SCLC) showed telomerase activity,while telomerase activity varied in non-smallcell lung cancers (NSCLC).

Normally, telomerase is inactive in somat­ic cells, which die natutally after a number ofcell divisions. Each time a chromosome isreproduced, the telomere, a small part at theend of the chromosome, is lost. In otder tocounter these losses, each of the chromo­some's re10meres carries repeating nucleotidesequences. However, once those sequences areused up, the cell StopS dividing and dies. Cellsthat need to continue to reproduce, such asgetm line reproductive cells, carty tdomerase,a DNA polymerase which adds repearingnucleotide sequences to the shortened tdom­eres. Previous studies have also found tdom­erase activity in malignanttumors of numerous cell typesincluding breast, prostate,colon, skin, and brain, suggest­ing that the enzyme allows can­cet cells to continue to divide.

The reactivation of tdom­erase may occur at either oftwo stages of cell death, mor­tality stage I (M I) or mortali­ty stage 2 (M2). During MI,cells lose theit ability to divide,a state known as senescence.The malfunction of a tumor­suppressor gene or the muta­tion of an oncogene mighttransform a cell, allowing it toavoid senescence. However,although such defects extendthe cell's life span, it will even­tually die. During M2, cellsreach a point known as crisis,in which most cells die; how­ever, the survivors are immortal and capableof unlimited prolifetation.

The presence of NSCLC tumors contain­ing both mortal and immortal cells suggeststhat the immortalization of an existing tumorcell is rare, requiring two separate events andoccurring after many cell divisions. In SCLCs,cells show signs of having already undergonethe number of divisions and chromosomalchanges necessary for the reactivation oftdomerase before becoming cancerous.

Shay and his colleagues observed varia­tions in relomerase activity that may reflectcharacteristics of the cells or the ratio of mor­tal to immortal cells within the tumors.However, although levels of telomerase activi­ty varied dramatically among some of thesamples tested, immortalized lung cancer celllines all showed similar activity, whetherSCLC or NSCLC. The study's authors cau­tiously suggest that once a lung cell is immor­talized, it achieves a set level of relomeraseactivity no maner what its type.

The absence of tdomerase activity in some

992 Volume 103. Number II, November 1995 • Environmental Health Perspectives

used to treat approximately 30,000 people inthe United States who have CML and AML.Experiments are also underway to test thisisoto!'" thetapy in other types ofcancers.

Radium is a very rare element. Thestockpile of radium-containing waste at theFernald plant is the largest cache in theworld. The 4,500 grams of radium present atthe site could provide thousands of doses ofthe new cancer treatment and has been esti­mated to be worth about $68 million. TheCOSt of extracting the radium has not beenestimated, and it has not been determinedwho would pay for it.

The waste has been scheduled to bemelted into a g1asslike substance through aprocess called vitrification in a joint cleanupeffort by the Depanment of Energy and theEPA. The DOE has contracted with theFernald Environmental RestorationManagement Company (FERMCO) tomanage the cleanup. "A pilot vitrificationrun is scheduled to begin in November" saidPerry Richardson, spokesperson for FERM­CO. "Depending on the pilot run, a full­scale cleanup could begin in mid-1996 andmay last rwo to three years."

Both the DOE and FERMCO opposedelaying the cleanup to remove the radium.Mike Jacobs, a public affairs officer at theDOE in Cincinnati, explains one reasonwhy: "The DOE gets a certain budget foreach site per year. If the radium extractionprocess is cosdy, it may deplete a majoriry ofthe cleanup funds." Jacobs asserts that theDOE "is open to any suggestions from themedical communiry" but says they have notreceived any formal requests to temporarilyhalt the cleanup to extract the radium.

The residents of the towns surroundingthe Fernald plant are excited that the cleanupis about to begin. "They, along with theDOE, EPA, and other groups, have wantedthe site cleaned up for years," said Jacobs.Although residents understand the potentialgood that the waste can contribute, theywonder why this issue did nOt surface earlier.Residents also have many questions regard­ing the logistics and the implications of radi­um extraction, few of which can be answeredsarisfacrorily, as no group has prepared anextraction plan.

Manoranjan Misra, a professor of chemi­cal engineering at the University of Nevada,Reno, is an expert in separation processes. Heestimates that radium extraction at Fernaldmay COst $5 to $6 million, not includingadditional COStS to refine and putifr the radi­um to be used as a medical therapy. Misraexplained a possible radium recovery processwhich uses physical separation and othertechniques: "Special chemicals are added tothe vast waste pile to dissolve barium and ura­nium and float them to the top. This tOP

layer will contain most of the radium[atrached to the barium) and will weigh in atabout five to ten tons. It can be removed andsubsequently processed into pure radiumwithout slowing the waste cleanup." TheDOE and FERMCO want the scientists toextract the radium from the vitrified material,although, according to Misra, there is noknown ptocess for doing this.

All parties involved in the Fernaldcleanup have Stated they would like to savethe radium if it is economically and logistical­ly possible. If Scheinbetg and other scientistsobtain positive clinical trial results with med­ical isotopes, the loss of the Fernald radium tothe cleanup process will really be a waste.

AT Gene IsolatedA gene that when mutated causes a rare andfatal hereditary disorder has been isolated bya team led by YosefShiloh, a geneticist ar TelAviv University in Israel. "This is a turningpoint in our understanding of AT [ataxiatelangiecsrasia], bur also in our understand­ing of cell growth and cancer," said Shiloh ata news conference announcing the discoveryof the gene. The research suggests that thegene may also be a major contributor tohereditary forms ofbreasr cancer.

Researchers hope the gene will aid indeciphering how cells wotk, as well as providenew understanding of how cancers develop."It's a biologically complex area [that wehave] very liede way of unraveling. By havingthe gene, we've broken the logjam," saidRichard Gatti, a member of the tearn at theUniversiry ofCalifornia at Los Angeles. "This.is a Rosetra stone gene," he said.

Scientists believe the gene encodes a pro­tein that recognizes DNA damage and haltscell growth and division until the damage isrepaired. In patients with AT, damaged cellscontinue to replicate and divide withoutbeing repaired. "The molecule ttansmits themessage [to hair cell division] to the cell, andsomewhere the telephone lines were down,"said Gatti.

The gene was located as the result of ahunt by four laboratories-Shiloh's, Galli's,one led by Malcolm Taylor at the Universityof Birmingham, U.K., and one led by PatConcannon at the Virginia Mason ResearchCenter in Seattle, Washington-using posi­tional cloning. "First we do linkage analysis,and then go in and pluck our the gene. It isdone purely mathematically," Galli said.

AT affects children, who inherit rwodefective copies of this gene (one from eachparent), at an early age, causing the deterio­ration of muscle coordinarion and defects inthe immune system. AT also causes extremesensitivity {Q radiation. sometimes to thepoint of futality. Patients with AT frequently

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develop cancers, usually leukemia and lym­phomas, and most patients succumb to thedisease by their 20s due to infection or can­cer. The disease affects about I in every40,000 people worldwide. About 500American children have AT, and an estimat­ed 2.5 million Ameticans are carriers of onecopy of the AT mutation.

Researchers are now studying the possi­biliry that carriers have increased risks ofcan­cer. It has been estimated that carriers arefour times more likely to develop cancer andthat female caniers have a fivefold increasedrisk ofdeveloping breast cancer.

A possibiliry is that the very proceduresused to decea breast cancer in women maybe increasing the risk of developing cancer infemale carriers because of its link to radiationsensitiviry. In 1991, Michael Swifr of NewYork Medical College in Valhalla proposedthat diagnostic X-rays might cause breastcancer in certain women. He showed thatwomen from AT families who have breastcancer were more likely to have been exposedto high-dose diagnostic or therapeutic X-raysthan fumily members without breasr cancer.This finding was consistent with data indi­cating that cultured cells containing themurated gene suffer more DNA damage andhave a higher death rate than do normal cellswhen exposed to X-rays.

Swift's theory is controversial because theamounts of radiation used in current diag­nostic X-rays are lower than an individual'snormal annual exposure to natural radiationand lower than the doses given to the cul­tured cells. Now that the gene has beencloned, theories such as Swifr's can be tested.The National Center for Human GenomeResearch, the National Cancer Institute, andthe Danish Cancer Registry in Copenhagenare initiating srudies to research this possibili­ty. Meanwhile, the NCI has said that womenshould continue 10 follow the recommendedmammography screening for breast cancer."We hope to flOd [the gene's) role in radia­tion sensitivity, so that we can find our howto protecr and who to protect," said Galli."We can now do the experiments that with­out the gene we had no handle on."

Richard Paules, head of the GrowthControl and Cancer Group in the Labor­atory of Environmental Carcinogenesis andMutagenesis at the NIEHS says, "a betterunderstanding of this imporrant pathwaycon tolling cell proliferation holds thepromise of developing new diagnostic plOCe­dures and offers hope that scientisrs may beable to design beller therapies for cancers."

Environmental Health Perspectives • Volume 103, Number 11, November 1995 993

Blue Planct Prizc

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Outstanding in the Field

The pursuit of excellence in environmental health and science continues. Severalorganizations have recently acknowledged the success of individuals and

organizations in improving the environment.

General Motors Cancer Research Foundation AwardsIn a ceremony June 20 at rhe National Institutes of Health at Bethesda, Maryland, three $100,000 prizes wereawarded to scientists "who have made oursranding contributions in the fight against cancer."'1995 Charles F. Kettering Prize for Outstanding Contributions to the Treatment of Cancer-Norbert Brock, for­

mer chief of the Department of Cancer Research ASTA-Werke in Bielefeld, Germany. Brock made a break­through discovery of the synthesis and delivery of the chemotherapeutic agents cyclophosphamide and ifos­famide and continues research on making these agents safer and more effective.

•I995 Alfred P. Sloan, Jr., Prize for Outstanding Basic Science Contributions to Cancer Research-Edward E.Harlow, American Cancer Society Research Professor, Massachusetts General Hospital Cancer Center, HarvardMedical School. Harlow followed EIA, an oncoprotein produced by an adenovirus, to its cellular target, the

retinoblastoma susceptibility protein, and found that other viral oncoproreins disrupt cell cycle regulation. .• 1995 Charles S. Mott Prize for Outstanding Research in Cancer Causation and Prevention-Frederick P. Li, chief of the Division ofCancer

Epidemiology and Control, Dana-Farber Cancer Institutes, and Joseph F Fraumeni, Jr., director of the Epidemiology and BiostatisticsProgram, National Cancer Institute. Li and Fraumeni discovered an inherited cancer syndrome predisposing family members to severalcancers including sofr~tissue sarcomas, early breast cancer, osteosarcoma, acute leukemia, adrenocortical carcinoma, brain tumors, andtumors induced by radiation therapy. After connecting the newly named Li-Fraumeni syndrome with an inherited p53 gene alteration, theresearchers formulated recommendations for genetic testing.

Blue Planet PrizesOn November 2, the Asahi Glass Foundation of Tokyo, which was founded to further study the applied sciences,commended individuals or groups who have made major contributions [Q solving global environmental problems.Each winner received a ptize of 50 million yen (about $500,000).• Academic Award-Bert Bolin, professor emeritus at Stockholm University. Bolin was awarded for his groundbreak­

iog research on the carbon cycle and generating a model of me influences of oceans, atmosphere, and the bios­phere on global warming. Bolin has led numerous international scientific committees dedicated to the study ofclimate change and since 1988 has been head of the Intergovernmental Panel on Climate Change, an internation­al group of experts who suggest policies to halt global warming.

• Development and Implementation Award- Maurice Strong. Strong brought conservation and environmental issuesto the attention of political and business leaders as secretary-general of the 1972 UN Conference on the Human Environment and as the firsrhead of the UN Environment Program. Strong also served as secretary general to 1992 UN Conference on Environmenr and Development(rhe Earth Summit) in Rio de Janeiro, the largest environmental conference in history.

Global 500 Roll of HonourIn a June 5 ceremony in Pretoria, South Mrica, the United Nations Environment Program named 27 individualsand organizations, in youth and adult categories, Gobal 500 laureates for "outstanding achievements in the protec­tion and improvement of the environment." The following summaries represent the types of activities for which thelaureates were awarded.• George Monbiot, an investigative journalist from the United Kingdom. Monbior has worked to expose perpetra­

tors of environmental destruction and abuses of the rights of indigenous peoples. Monbiot wrote of his investiga­tion of rainforest destruction and wetland habitats and the dispossession of indigenous people in Irain Jaya (for~

merly part of New Guinea) in his book. PoisonedArrows.• Father Balernans, a priest from The Netherlands. BaJemans founded the Association pour Ie Developpement de la

Region de Kaya to teach rural communities natural resource management and sound agricultural practices to avoid desertification.Twenry-five villages in Butkina Faso have successfully implemented Baleman's model.

• Sajina Z Siddiqi of Pakistan. Siddigi founded the Karachi Administration Women's Welfare Sociery as part of a campaign to improve localliving conditions. The women established a garbage collection system and eight parks, planted saplings, and pressured rhe local authorities to

help them make road and sewer repairs.• Yokkaichi City, Japan and Mayor Kamhi Kato. Notorious for its smog in rhe I970s, the Yokkaichi Pollution Control Board instituted a suc­

cessful pollution control project integrating environment and development that resulted in cleaner air. They also pioneered public medicalcare programs to help patients wirh pollution-related respiratory diseases.

• The Green Machine Nature Conservation Club of Sunridge Primary Schoo!' This student group, in one of the mosr underprivileged sections ofSouth Mrica, ran soup kitchens, organized workshops for narcotic addicts, cleaned up J squattet settlement, created a park, instituted a pro­gram to exchange reeyc1ables for food packers, and initiated an environmental awareness campaign.

994 Volume 103. Number 11. November 1995 • EnVIronmental Health Perspectives

The Coastal Society

Seeking Balance:Conflict, Resolution and Partnership

15th International ConferenceJuly 14-17, 1996

Seattle, Washington

~-o;:::;-~-.....::Abstracts -~ ~~----= iJ.~

Abstracts should be no longer than one single-spiilc 1-2 Ige and include the name,

title, affiliation, mailing address, phone and fax numbers, and email address (if available) of

each author, and the broad topical area where the paper might best fit in the program.

Abstracts and proposals for special topic session must be received no later than November 1,

1995. Please send to:Megan D. Bailiff, Conference Chair

The Coastal Society 15th International Conferencec/o Washington Sea Grant Program

3716 Brooklyn Ave. NESeattle, WA 98105

Phone: (206) 685-1108 Fax: (206) 685-0380mbailiff@u.washington.edu

NIEHS News

In 1993. researchers at Rutgers Uni­versiry successfully produced an X-ray crys­tallography structure of the HIV RTbound to DNA. Although this was a majorbreakthrough, it did not answer all thequestions. Kunkel has since turned to theNIEHS's computer modelers to take thislow resolution information and build apredictive model of the RT ro suggest fur­ther areas of experimentation. "The crys­tallographic information basically providedme with a bunch of isolated poinrs inspace," says Darden. "Using a computer, Ihunted through the database of knownproteins to find fragments to fit thesepoinrs. and ended up with a model of whatthe structure might look like."

According to Kunkel. the model sug­gested changes that could be made in theregion of interest that will help researchersunderstand precisely how the enzymebinds irs substrates. "With such under­standing," Kunkel says, "there is a betterchance of being able to design more effec­tive drugs."

Making Sense of MetabolismComputer modeling is also aidingMasahiko Negishi. head of the pharmaco-

Thomas Kunkel and Kasia Bebenek

AZT by rapidly mutating. Designing adtug ro suppress the virus depends onunderstanding exactly how it mutates.

In 1988. Kunkel demonstrated thatreverse transcriptase (Rn, the enzyme thatHIV-1 uses to replicate the genome.exhibirs a high rate of mutations that resultfrom slippage of the template with respectto the primer strand of DNA. Researchersthen set out to understand what parts ofthe enzyme were responsible for this phe­nomenon. Kunkel's team chose a region ofthe RT protein and began making a seriesof mutant RT proteins, replacing variousamino acids and analyzing their effect onDNA replication. The team identified sev­eral residues that lead to slippage of theDNA strands. but because they lackedhigh-resolution structural data. they werenot able to rationalize how this occurred.

the force fields that determine howatoms interact with each other.With this information, scientistscan use Newton's equations of

motion to study the dynamics of themolecules. Because of the enormous

number of equations that must be solvedto simulate the motion of a macromoleculefor even a billionth of a second. this canonly be done by high-speed computers.

Not only is the computational speedoffered by computers essential to under­standing molecular form and hlOction, sotoO is graphical representation. Computergraphics provide highly detailed informa­tion about the arrangement of molecules inspace the only way humans can readilycomprehend it-visually.

In the typical representation. called awireframe, lines depict bonds betweenatoms with each endpoint representing anatom. These lines can be colored based onatom type for easy identification. Because amacromolecule may consist of more than3.000 aroms. the ability to isolate andenlarge details is important. With a singleclick of the computer mouse, researcherscan magnify a small portion of a moleculeor view just the backbone StruCture.Another command allows the researcher toinstantly measure the distance betweenatoms. The structure can even be rotatedto observe how the atoms are arranged inspace. "The important thing about a com­puter representation is that you can ask alot of questions that are not answerableexperimentally," says Darden, such as"What's the relationship between twOatoms over time? Do they ever cometogether?"

Computer VirusesUnderstanding molecular dynamics is espe­cially crucial in drug design. In their searchfor the discovery of substrates or inhibitorsthat will bind ro a key enzyme. researchersmust know the precise shape of anenzyme's binding site and the dynamics ofthe enzyme and drug. Computer modelingoffers a technique for characterizing sub­strate-enzyme binding that can assistresearchers in identifying and synthesizingclinically effective compounds. Likewise.researchers seeking to understand theeffects of environmental toxicants mustidentify rhe cellular receptors with whichthe compounds interact.

Research geneticist Thomas Kunkelheads a project that seeks to understand thefideliry of DNA replication. particularly asit relates to the HIV-l virus that causesAIDS. HIV-l escapes an individual'simmune system and resists drugs such asTom Darden

Bodies in MotionComputer modeling offers distinctivecapabilities for deciphering resulrs of otherStructural modeling techniques. Crystal­lography, for example. provides high-reso­lution snapshots of molecular structures inthe solid state. However, molecules in solu­tion are in constant motion, and a morecomplete picture requires a knowledge oftheir molecular dynamics. Quantum chem­ical calculations and various experimentaltechniqu.es enable researchers to describe

ModelingMacromoleculesSince 1953, when JamesWatson and Francis Crickpresented their double helixmodel of DNA, the field ofstructural biology has exploded.New technologies have led to rapid break­throughs in understanding the form andfunction of a wide range of macromole­cules.Indeed, most studies of life at themolecular level are now considered incom­plete without three-dimensional structuresto guide further research.

Structural biologists today use tech­nologies such as nuclear magnetic reso­nance (NMR) spectroscopy, X-ray difftac­tion crystallography, electron microscopy,and computet modeling to discovet anddefine the form of macromolecules. Usedtogether, these technologies often provide amore complete picture of biological phe­nomena than any single technique.

Researchers at the NIEHS have empha­sized computer modeling and NMR. Theinstitute was one of the first in the nationto purchase silicon graphics workstationsthat are now considered essential to model­ing and visually displaying molecules.Today, using far more advanced systems,the NIEHS maintains a computer model­ing group led by mathematical statisticianTom Darden that provides institute scien­tists with computational approaches tocomplex research questions. Several othergroups at the NIEHS also use computermodeling in their research.

996 Volume 103, Number 11, November 1995. Environmental Health Perspectives

NIEHS News· Modeling Macromolecules

Masahiko Negishi

genetics section of the Laboratory of Re­productive and Developmental Toxi­cology, in his study of P450s, a family ofproteins that plays a key role in metabo­lism. P450s exhibit remarkable substrateand product diversity. Two P450s maydiffer by less than 10 amino acids out of500, but this subtle difference may signifi­cantly affect an individual's ability tometabolize various drugs and chemicals.Specificiry of P450 activiry can be alteredby a single amino acid substitution at akey position. Based on such differences,one person may be able to take 10 timesmore of a dtug than another individual, orthe same dose of a drug may cure one per­son's symptoms but cause adverse sideeffectS in another. "If, for a given individ­ual, we can pinpoint amino acid muta­tions at particular points, we might beable ro predict their reaction to certaindrugs or chemicals and warn them awayfrom those that may cause them trouble,"says Negishi.

To identify which amino acids are ctit­ical and at what times, researchers mustunderstand the structure of the P450.Bacterial P450 is easy ro crystallize, so itsstructure can be easily determined.However, mammalian P450 has so farbeen resistant to crystallization. Its struc­ture can only be inferred through comput­er modeling. This is where Darden's teamcomes in.

Proteins with similar sequences ofamino acids usually adopt similar orienta­tions. Therefore, Darden gatheted thestructural information known about thebacterial P450 and information producedby Negishi's team through site-ditectedmutagenesis and enzyme analysis of mam­malian P450. Using sequence homology,Darden was able to compute which aminoacids in the bacterial enzyme correspondto the mammalian amino acids, resultingin a proposed struCture for the mam­malian protein. Negishi is currently exper­imenting with binding various substrates

to the modeled mammalian P450 to pre­dict how a particular mutation affects theactiviry of the enzyme.

"There are two benefits I get from themodeling," Negishi says. "I can get somehypothesis as to why the mutations we seein the mammalian enzyme affect the sub­strate specificiry. And knowing why thismight be so, I can do further research. Wecan go back to test the hypothesis that, forexample, the size of a particular aminoacid is crucial.»

Genes on ScreenComputer modelers are using a similarprocess with Roger Wiseman, director ofthe Laboratory of Molecular Carcino­genesis, in his search to understand theworkings of the BRCAI gene. BRCAIplays a key role in hereditary breast andovarian cancers. The gene appears ro func­tion as a tumor suppressor, but a mutationaffecting a relatively small number ofamino acids at the amino terminus of theprotein appears to decrease the gene's abil­iry to regulate cell growth and to increasean individual's chance of developing can­cer. Wiseman has called upon NIEHScomputer modelers to create a three­dimensional model of this section of theBRCAI protein to predict how it foldsand to determine which residues are onthe outside, interacting with other pro­teins and DNA.

Using the sequence of amino acids forBRCAI and the sequence of a related her­pes vitus protein for which the sttucture isknown, computer modeler RachelleBienstock ran a series of homology studiesto come up with a model. "From thismodel, I suggested some residues in theprotein that might bind to the DNA, andI suggested some experiments that couldbe done to mutate the protein to see if itchanges the binding affinity," saysBienstock. "The more we learn about thepathway the gene takes in mutating, themore we have a chance (0 imervene."

Shlron Brylnt

Drug DesignComputer modeling is also helping tounravel the secrets of opioid peptides usedin the treatment of pain. The medicinaluse of these peptides, particulatly thosederived from frog skin secretions, datesback to ancient Assyria and Babylonia.The indigenous peoples of the AmazonBasin still use poisonous frog skin secre­tions to coat the tips of their blow-gundartS and in shamanistic rites. Scientistsbelieve these unique peptides might havepotential applications as therapeutic andclinical compounds in the management ofchronic and acute pain and in the treat­ment of narcotic addiction, alcohol depen­dency, and suppression of the immuneresponse during transplant surgery.

Rlchelle Bilnstock Ind Rog.r Wis....n

Over the past six years, LawrenceLazarus, head of the peptide neurochem­istry section, has directed a project at theNIEHS that involves synthesizing and ana­lyzing deltorphin and dermorphin analogsthat ate hundreds of times more potentthat the endogenous mammalian opioidpeptides (see EHP vol. 102, no.8, pp.648~54).The ultimate goal of the projectis to design new and more potent opioidagonistS and antagonists that are clinicallyapplicable. Sharon Bryant, a chemist in thegroup, uses molecular modeling to deter­mine structural motifs of opioid peptidesto predict sttucture-activiry relationships."Computer modeling helps us to visualizepossible orientations of amino acids in themolecule," Bryant says. "It also helps us rounderstand the intermolecular dynamics.Knowing the orientation of the structurein three-dimensional space would enhanceour effons to design agonists and antago­nists." Lazarus and his team have devel­oped a number of dual-affiniry agonistsand ultraselective opioid antagonists whichare currently being tested for their applica­tion to human health.

John Manuel

Environmental Health Perspectives. Volume 703, Number 77, November 1995 997

r breast cancer in women i

and plOSlate cancer in men 1rose dramatically during the ,

period of the srudy, due largelyto increased detection, and that

several types of cancer are becomingmore common for reasons that are

unclear. Of particular concern are increasedincidences of non-Hodgkin's lymphomaand brain, kidney, bladder, and testicularcancers.

The Causation DebateResearchers have put forth a variety of the­ories for the increased incidence of somecancers, including a population that isgrowing and aging, berter screening tech­niques, earlier diagnosis, and the impact ofenvironmemal and occupational exposureto chemicals. The latter is probably themost controversial of these theories anddivides the players in the debate.

"Cancer is an important public healthproblem in this countty," says Susan S.Devesa, team leader of the NCI srudy andchief of the Descriptive Srudies Section ofthe Epidemiology and BiostatisticsProgram at NCI. "But, with respea to theconcern that we might be having largeincreases in cancer incidence due to envi­ronmemaJ influences, I think our studiesshow that is not the case."

Overall, Cole agrees with Devesa, andchides those who predict an impendingcancer disaster. In his Februaty 1 editorialin jNCI, tided "The Evolving Picture ofCancer in America," Cole suggests thatovet the past 20 years the popular mediaand some scientific literature have impli­cated the pollution of the general environ­ment as causing cancer incidence [Q

increase. He stresses that these "pro­nouncements" contained sensational ele­ments and resulted in the call for morestringent environmental regulations.Ultimatdy, Cole does not deny that our air

changes that have OCCUtred regarding inci­dence from the mid-1970s to early 1990s,and contrast incidence and mortalitytrends to provide clues to the determinantsof temporal parterns. Cancer incidence andmortality rates were collected from 1987 to1991 and compared to those from 1975 to1979. Findings of the srudy were publishedin the 1 February 1995 issue of the jou"",1ofth' National Cane" Instituft.

The team used data from the latest edi­tion of NCl's annual update of cancer sta­tistics, compiled by the SEER Program(Surveillance, Epidemiology, and EndResults), which has monitored the occur­rence of cancer and survival of patientssince 1973. The update reports and sum­marizes cancet's impaa on the U.S. popula­tion and monitors statistics to assessprogress and identify areas where controlefforts should be concentrated. The NCIresearchers found that trends in cancer dif­

o fer according to the type of dis­~ ease and, although mortality~ rates for all cancers combined~ have risen among men and1women, mostly due to increasesm in lung cancet mortality, death

rates for the majority of cancersare steady or declining. Re­searchers artributed the declinesprimarily to changes in lifestyle,earlier detection of disease, andimproved trearment.

The jNCI article also con­cluded that the incidence of

S_n S. Dovesa-Incr••s­es in cancer incidence arenot due to environment

;.

\. .''It.._q,~...._~In the United States, the ~alarming statistics concerning ,~: !~,

cancet ate that in a few ShOll ;. ~ r-J '~'~~~"'~~~lii:ryears it will surpass hean disease " . .. L:€~. f ..~as the ptedominant cause of death ~~ :; ·T~.~' ....in this coumry. one in three people 1 ~;~ .. '

will be diagnosed with it in their lifetime, ,and one in five will die from it. A largeproportion of cancer deaths can be attrib­uted to lifestyle factors such as tobacco useand diet and thus are avoidable. Still othersmay be linked to occupational and envi­ronmenral exposures that individuals havelittle or no control over.

In an effort to reduce this enormouscancer burden, the United States mandatedthe National Cancer Act of 1971. Morethan rwo decades later, gains have beenmade but the eradication of cancer remainsan dusive goal. Even when cancers causedby smoking are disregarded and the agingof the U.S. population is taken into ac­count, an upward trend of malignancy isstill evident, though researchers debatewhether seeming increases in incidences arereal or due to improved diagnosis, andopinions vary on cancer causation. "Wheth­er or not the rates are rising or l3lling doesnOt seem to me a debatable issue," saysPhilip Cole. a professor of epidemiology atthe University of Alabama, Birmingham."Some rates are rising, some are falling,some are steady. This is afactual observation. What isdebatable might be whetheror not the seeming rise isreal, or whether or not theseeming declines are real,and what each is due to.»

Cole's mention of "afacrual observation» refers tothe recent effort ofa team ofresearchers at the NationalCancer Institute (Q identifycancers accounting for risingincidence rates. quantify

Focus

998 Volume 103, Number 11, November 1995 • Environmental Health Perspectives

Focus· The Cancer Conundrum

~ would increase. and fewerli people would be able to buy

fruits and vegetables.In a chapter in the book,

The True State of the Planet(Free Press, 1995), Ameswrites, "Because of theirunusual lipophilicity andlong environmental persis­tence, there has been panicu­lar concern for a small groupof polychlorinated syntheticchemicals, such as DDT andPCBs. n Ames states thatthere is no convincing epi­

demiological evidence and lirtle tOxicologi­cal plausibility that the levels of thesechemicals found in the environment arelikely to be a significant contributor tocancer.

"Of course we need rules to use thesechemicals, but we don't need to spend2-5% of the gross domestic product chas­ing after parts per billion [levels] that arenot going to have anything to do withcausing cancer," says Ames. "People aregetting distracted with a million hypotheti­cal risks that aren't really risks. A lot ofmoney is being spent because it's beenhyped up that the chemical industry is giv­ing people cancer. There are a lot of people

David P. Rail-No oneknows how chemicals affectcancer rates.

According to the NationalCancer Advisory Board (NCAB)in the September 1994 repon,Cancer at a Crossroads: A Reportto Congress for the Nation, "Weare just beginning to under­stand the full range of healtheffects resulting ftom the expo­sure to occupational and envi­tonmental agents and factors."Consequently, the NCAB sug­gests the elimination or reduc­tion of exposure to carcinogenicagents, including pesticides andother synthetic chemicals, as aprioriry in the prevention ofcancer.

Bruce Ames, director of the Environ­mental Health Sciences Center at theUniversity of California at Berkeley,believes such measures could result in sub­scantial increases in the risk of cancer. Amesfirmly believes that pesticides are one ofthe major public health advances of thiscentury. He contends that one-quarter ofthe U.S. population's intake of fresh fruitsand vegetables is inadequate, and that con­sequently their chromosomes are brealringdown due to a lack of the vitamins folicacid and ascorbic acid. Ames says the elim­ination of pesticides would promote cancerrisk because fruit and vegetable prices

and watet contain substances labeled ascarcinogenic by vatious agencies. He does,howevet, challenge the validity of suchevaluations. "What is not correct is thatthese airbome Ot watetbome levels of car­cinogens have been shown to cause cancerin human beings," says Cole.

According to David P. Rail, tetitedassistant surgeon genetal with the PublicHealth Service and fotmet ditectot of theNIEHS, there is no such thing as ptoofwhen it comes to assessing the impact ofpotential envitonmental and occupationalcarcinogens on human health. "That's theteal ptoblem," RaIl says. "Nobody knowshow much envitonmental and occupationalchemicals affect the overall cancet tate.Epidemiological studies have such a highthreshold that it's very difficult to ptoveanything." With the burden of ptoof inmind, RaIl believes that mote effective epi­demiology studies are needed, and he ques­tions the contention made by Devesa andothers that incteased scteening accounts formost of the recent increases in cancer inci­dence. "The increase in incidence has beensteady, and if in fact this were due to bettertechnology, the incidence should have goneup in jumps as CAT scans and magneticresonance imaging were developed. Thatdidn't seem to happen," he says.

Trends in U.S. Cancer Mortality Reles

lung (femalesl 131.5

Melanomas of skin 35.2

Non·Hodgkin's 33.2

Multiple myeloma 31.1

liver & Intrahepatic

Prostate

lung (males)

Kidney/Renal

Brain &Nervous System

Esophagus

All cancers 6.9

Breast lfemalesl 1.8

Pancreas .1.4

leukemias -4.6 Ilarynx ·4.8 IOvary ...7 I

Colon/Rectum

Oral Cavity &Pharynx

Urinary bladder

Thyroid

Uterus

Stomach

Cervix

Hodgkin's

Testis ....·150 ·100 ·50 50 100 150

Percent change, 1973-91

94.0

~;::::126.3..: 118.0

-27.7

·36.4

Trends in SEER Incidence Reles

·lSO -100 -so 0 so 100 1SO

Percent change, 1973-91

Hodgkin's

Stomach

Thyroid

Multiple myeloma

Esophagus

Urinary bladder

lunglmalesl

Ovary

Colon/Rectum

larynx

Oral Cavity & Pharynx

Pancreas

leukemias

Uterus

Cervix

lung (femalesl

Melanomas of skin

Prostate

Non-Hodgkin's

liver & Intrahepatic

Testis

Kidnev/Renal

Brain &Nervous System

Breastlfemalesl

All cancers

Source: SEER Cancer Statistics Review, 1973-1991.

Environmental Health Perspectives. Volume 103, Number 11, November 1995 999

Focus' The Cancer Conundrum

Bruce Ames-People aregening distracted by hypo·thetical risks.

that have a big self-interest in this hype,and there's really no evidence to support it;it's implausible."

Another voice that is rarely heard inthe debate on cancer, but one which pro­vides a different perspective on the impactof environmental and occupational factorson cancer, is that of the ecologist, saysSandra Steingraber. Steingraber, a biologistat Nonheastern University whose focus isin community ecology, is the author of aforthcoming book on cancer and rhe envi­ronment. She says that ecology, a disci­pline that muggles to make sense of multi­ple effects and exposures, offers greatinsight into cancers because they arecaused by multiple factors and are subjectto a kaleidoscope of changingevents.

"You miss a lot of the biggerpicture of cancer if you rake akind of physics approach to it,"Steingraber says. "Often verysmall changes are exerted overlong periods of time that eventual­ly accumulate and create vety dra­matic changes in the ecosystem."

Steingraber offers RachelCarson as an example of a scien­tist whose ecological approach towildlife biology resulted in somestartling realizations that were awake-up call to American society afterWorld War II. "No one before her graspedthe significance of ... blanketing thecountryside with pesticides, of what poten­tial human health effecrs might be trig­gered ... through routes that seem nowvery obvious to us,» she says. "It took anecologist's more holistic perspective. some­body who was used to thinking andtrained to think about multiple pathwaysand indirect effecrs to bting this into thepicture."

The EvidenceAs scientists choose sides in this increasing­ly mong debate, there is one point thatfew choose to argue: chemicals that canpotentially affect the risk of human cancerare everywhere-in the food we eat, thewater we drink, the air we breathe.Researchers worldwide are continuallyuncovering evidence that pesticides, toxicair pollmants, heavy metals, and variousforms of radiation can promote cancer inhumans.

Persistent pesticides. Certainly, greatbenefits have been derived from agrochem­icals and pesticides, not the least of whichis the ability to produce large amounts offood crops at a savings of millions of dol­lars a year. At the same time, scientific lit­erature is replete with evidence of the car-

cinogenic properties of various pesticidechemicals. Fot example, otganophosphateinsecticides have been linked with a risk fornon-Hodkgin's lymphoma, and organo­chlorines, including DDT, have been asso­ciated with leukemia. Animal and epidemi­ological studies have shown an associationbetween non-Hodgkin's lymphoma andbrain and kidney cancer and exposure topesticides or solvents such as gasoline.

Research on farmers' health has shownthat though they tend to live longer andhealthier lives than the general populationand have impressively low rates of heart dis­ease and other ailments, for decades farmershave exceeded the national average for cer­tain cancers, including leukemia, multiple

~ myeloma, non-Hodgkin's~ lymphoma, and cancers of~ the brain, prostate, stomach,

skin, and lip. NCI research­ers believe that such labora­tory and epidemiologicalfindings may suggest broad­er public health implica­tions, as several of themalignancies associated withfarmers appear to be on therise in the general popula­tions ofseveral countries. .

"In addition to pesti-cides, farmers incur chronic

exposures to potentially harmful com­pounds, such as engine exhausts, chemicalsolvents, fuels, animal viruses, and sun­light," says Devra Lee Davis, a presidentialappointee to the National Chemical SafetyBoard and a senior advisor in the Depart­ment of Health and Human Services."Could increasing exposures to similarmaterials in the general population accountfor the fact that some cancers that are ele­vated in farmers are also increasing indeveloped countries?"

The Agricultural Health Study, a jointproject of the NCI, EPA, and NIEHS, ini­tiated in January 1993, is the nation'slargest epidemiological study of farmersand their families to date. Over a 10-yearperiod, investigators will work to idenrifyand assess factors that may account forthese cancer excesses among farmers.

In a number of laboratories around theworld, researchers are finding evidence thatsome chemicals used in pesticides maycontribute to cancer risk by mimicking theeffects of the hormone estrogen in thebody. Cancers that develop in reproductivetissues, such as breast, ovary. endometri­um, and prostate, are dependent on aninteractive network of various hormones,including emogen, for their muctural andfunctional development. Findings suggestthat pesticides such as DDT, heptachlor,

and arrazine, as well as several polycyclicaromatic hydrocarbons, petroleum by­products, and PCBs, possess estrogenicproperties.

"We are particularly concerned aboutmaterials called xenoestrogens, a numberof petsistent, widespread environmentalchemicals that have clearly been demon­strated to disrupt the endocrine systemexpetimentally," says Davis, who, alongwith colleagues Erin Blair and JosephFraumeni ofNCI, coined the term "xenoe­mogen" in 1993. "When exposed to them,the body altets the production and metab­olism of its narural levels of emadiols."Davis is a key architect of the theory thatxenoestcogens are a preventable cause ofbreast cancer. She says that evidence impli­cating xenoestrogens as a factor in the cau­sation of breast cancers includes cell cul­ture experiments, animal experiments, andhuman and wildlife observations.

Conclusions of recent animal studieshave indicated a relationship between thelevel and duration of estrogen exposureand tumor development in hormonallysensitive tissues and between environmen­tal estrogens and testicular abnormalitiessimilar to those reported to be on the risein men, which include not only cancers,but undescended testicles and defectivesperm. Decreases in sperm quality in oth­etwise healthy men over the past severaldecades have been reported worldwide."Taken together, this growing body of evi­dence suggests that environmental factorsthat resemble female sex hormones may behaving an adverse effect on the reproduc­tive health and well being of diversespecies," Davis says.

Air pollution. Many air pollutantsaffect the mucous membranes of the respi­ratory tract and can contribute to theoccurrence or aggravation of disease,including lung cancer, the leading cau'-e ofcancer deaths in the United States.

Of the tons of matetial emitted annual­ly into the air, five major pollutantsaccount for close to 98% of overall pollu­tion. These are carbon monoxide (52%),sulfur oxides (18%), hydrocarbons (12%),particulate marter (10%), and nitrogenoxides (6%). In regard ro the conttibutionof these pollutants to cancer, the weight ofevidence varies from limited to substantiaLAccording to Steingraber, of these five sub­stances, it's difficult to discern which onescontribute to the growth of specific cancersin humans because people are typicallyexposed to them simultaneously.

"It's rare that you can go someplace inthe world where you've got a lot of partic­ulate matter but no hydrocarbon vapors, ora lot of sulfur dioxide but no particulates,"

1000 Volume 103, Number 11, November 1995· Environmental Health Perspectives

Pltlr Shlilds-Assessinginterindividual variation is adifferent approach to risk.

Steingraber says. "In urban environmentsthese substances come as a package.Therefore, the best we can do in humanstudies is attempt to determine if air pollu­tion and lung cancer or air pollution andother kinds ofcancers are associared.»

Steingraber points out that though airpollution alone may be a weak carcinogen,it may be a significant factor in encourag­ing the growth and spread of cancer whenmixed with exposures to other subsranees,such as the indoor air pollurants formalde­hyde and tobacco smoke.

"Air pollution may contribute to a lotof cancers, but only because it's the strawthat breaks the camel's back: she says."There is some evidence from animal stud­ies indicating that air pollutants, such asnitrogen dioxide, encourage more rapidgrowth and dissemination from cancer,perhaps by making the lungs more vulner­able to metastases from other primarytumors. The relevance of these studies tohumans has yet to be shown.»

Despite this uncertainty, available dataindicate numerous toxic air pollutants maybe impottant contributors to cancer inci­dence. These pollutants include metalssuch as chromium and arsenic, asbestos,products of incomplete combustion,formaldehyde, benzene, ethylene oxide,gasoline vapors, and chlorinated com­pounds such as chloroform, carbon tetra­chloride, and trichloroethylene.

Environmental tobacco smoke. On 7January 1992, the EPA released a report inwhich environmental tobacco smoke(ETS) was classified as a group A carcino­gen-a category reserved for the most dan­gerous cancer-causing agents in humans,such as asbestos, benzene, and radon. Thereport, IInpiratory Htalth Effiets ofPassivtSmoking: Lung Cancer and Other DiJordm,indicated that in 24 out of 30 independentstudies, an increased risk of lung cancerfrom secondhand smoke was observed innonsmokers. EPA scientists estimate thatETS causes about 3,000 lung cancer deathseach year.

ETS is the combination of sidestrearnsmoke (smoke emitted berween pulIS of aburning cigarette, pipe, or cigar) andsmoke that is exhaled by the smoker. ETScontains essentially all the same carcinc­genic and toxic agents that have been iden­tified in mainstream smoke inhaled by

. smokers. Of the 4,000 individual com­pounds identified in tobacco and tobaccosmoke, about 60 have been identified ascarcinogens, tumor initiators, and tumorpromoters. Some of these compoundsinclude tar, carbon monoxide, hydrogencyanide, phenols, ammonia, formaldehyde,benzene, nitrosamine, and nicotine.

Focus· The Cancer Conundrum

Illuminating cancer at the Molecular Level

Technology is illuminating new strategies and methods for assessing can= risk that will aidin the identification and diagnosis of the disease at its most primary foundation---the molec­ular level.

"People are now able to study what chemicals are doinginside cells that affects the growth control of cells," saysJeanette Wiltse, associate director for health at the NationalCenter for Environmental Assessment at the EPA "The differ­ence berween the way can= assessments were done in the pastand the way they're going to have to be done in the future isthat we will pull this new information and technology intoassessing whether a compoun~ chemical-that we're look­ing at has carcinogenic potential or not.»

Wdtse is a member of the team responsible for updatingthe EPA guidelines for cancer risk assessment. The new guide­lines will require regulators to incorporate such factors as how a Jel_ Wiltse-Molecularchemical's srruetutal features might affect its toxicity and how biology is the basis of newa chemical is absorbed, metabolized, and distributed in the guidelines on risk.body into chemical regulations. This new tack is being hailed as a major shift in the EPA'sregulation of toxic chemicals.

"A whole new science has come out of the research of the last five to seven years," saysWdtse. "Our old guidelines were based on data from 10 years ago. BasicaUy, we're updating theguidelines to take into account this new information about the molecular biology ofcan=.»

Cunendy, the most simple and straightforward conceptual approach to quantiJYing andqualifying causes of can= at the molecular level entails using carcinogen-DNA adduces toidentifY how chemicals bind to DNA and cause mutations, explains Perer Shields, acting sec­tion chief in the Molecular Epidemiology Section of the Laboratory of HumanCarcinogenesis at NCl. But Shields adds that the technology is far from simple.

In the past, the ability to measure the number ofadduces in an individual's DNA provid­ed researchers with a marker ofexposure. Today, it provides much more than that. "This iswhere the field has evolved and matured over time," Shields says. OWe understand that theprocess leading to cancer is quite complex, and that humans as biological creatures are wellprotected. The point is that we've learned these adduces are also markers of how the bodyhandles exposure, of how it absorbs and metabolizes chemicals, how it escapes detoxifica­cion."

Afurther extrapolation of this approach to risk assessment is a concept Shields refers to as"interindividual variation," or the detection of subpopulations of sensitive or resistant indi­viduals. "The body's ability to activate, deroxi/Y, and repair itsdf is different from person to

u person," he says. "JUSt as the color of our eyes are different, soZ are our livers, and our repair mechanisms. Figuring out a way

to detect these sensitive individuals and sensitive subpopula­tions might enable us to elucidate new causes ofcan=."

For example, the identification of specific genes and theirdilferent forms could provide researchers with clues about anindividual's capacity for responding to exposures. Shields cau­tions that the field is young and that at this time it is consid­ered a major achievement when scientists are able to demon­strate a direct genetically mediated effect.

OWe're thinking ofeveryone as individuals now, and that'sa fundamental difference,» Shields says. "There could be subdedifferences in the population that we don't know how to quan­titate yer. For example, in approaching something like breastcancer, we're thinlting that maybe one type of breast cancer in

some women is cdated to one exposure and one susceptibility, and another type of breastcancer in another group ofwomen is related to a different exposure and susceptibility.»

In September 1994, researchers at the NIEHS and the University of Utah isolatedBRCAl, a gene that may account for some inherited breast and ovarian cance". This genecould be used to identifY women who would benefit ftom screening for early detection ofcance". This discovety confirms the capacity of new molecular strategies for elucidatingcauses ofcancer.

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1001

Focus· The Cancer Conundrum

By 1964 sufficient epidemiological dataon smoking and health were available tosupport the claim thar cigarette smokingcaused lung cancer, but it was not until1986 rhar reports from the InternationalAgency for Research on Cancer (!ARC),the U.S. Surgeon General, and theNational Research Council concluded tharpassive smoking caused lung cancer innonsmokers. Over the years, numerousepidemiological studies have supportedand reinforced their conclusions. Studiesfrom the early 1970s consisrently suggestedthat children and infants exposed to ETSexperienced significantly elevated rates ofrespiratory symptoms and respiratory traerinfections. Throughout the 1980s, epi­demiological studies indicated that non­smokers married to smokers were at anincreased risk for lung cancer. In addition,studies have shown that industrial workersare especially susceptible to lung diseasesdue to the combined effects of cigarettesmoke and exposure to certain toxic sub­stances present in the workplace.

Metals. The EPA and !ARC classifYarsenic as a carcinogen for which there issufficient epidemiological evidence to sup­port a causal association berween exposureand skin cancer. Arsenic, a naturally occur­ring, toxic meral, is released into the envi­ronment narurally by solubilization fromgeologic formations into water supplies. Iris also released inro occuparional and com­muniry environments by such activities asnonferrous ore smelting and combustionof fuels containing arsenic.

According ro Janice Yager and JohnWiencke in a 1993 supplement toEnvironmental Htalth Perspectives (vol.101, no. 3), srudies of occupational expo­sure [0 high concentrations ofarsenic in airat copper smelters and communiry expo­sure to arsenic in drinking water indicatean increased risk of lung and skin cancer,respectively. These authors also reportedrhat exposure to arsenic via drinking waterin Taiwan may have lead to increases incancer at other sites, such as the bladderand kidney, and that epidemiological stud-

ies have indicared synergism berweenarsenic exposure and cigarette smoking insmelter workers in the induction of lungcancer.

Some studies have indicated an associa­tion berween exposure to inorganic arsenicand the development of lymphoma, lung,bladder, and skin cancers. Such effects maybe due to arsenic acting in concert withother substances in the environmenr.Resulrs of animal studies also support thetheory that arsenic acts with other agentsto alter or enhance carcinogenesis.

Cadmium is ubiquitous in the environ­ment. Its most common natural form iscadmium sulfide, which is generally com­plexed with zinc, lead, copper, or iron, andis recovered as a by-produer from the pro­cessing of these ores. The general publicmay be exposed ro cadmium predominant­ly through contaminated food and waterand by inhalation ofcigarerre smoke.

There have been numerous reports ofthe acute and chronic effects of cadmiumin humans following accidental or occupa-

leading Sites of New Cancer Cases and Deaths -1995 Estimates

Concer Co... by S~e Ind Sex

Mill Femlle

Cancer CISIS by Site Ind S.x·

Mile Femoll

ProState244.000

lung96.000

Colon' Rectum10.700

Bladder31.300

lymphoml34.000

0,"118.800

Mellnoml of the Skin18.100

Kidnl'11,100

leukemia14.100

Stomach14.000

Pancreas11.000

lorynx9.000

All sitlsrn,ooo

Br••st182.000

lungn.-

Colon' ....&7'-.......

All sitlS575.000

lung95.400

Prostate40.400

Colon & Rectum21.zoo

Pancreas13.zoo

lymphoml12,820

leukemia11,100

Stomlch8,800

Esophlgus8.zoo

liver1.100

Blldder1.500

Brain1.300

Kidnl'11,100

All sites289,000

lung62,000

All sites258.000

'Excluding basal lind squamous cell skin cancer and carcinoma in situ.

1002 Volume 103. Number 11. November 1995· Environmental Health Perspectives

Focus' The Cancer Conundrum

Sand.. Slei..,.ber-Ecolo­gy offers a holistic perspec­tive on cancer causation.

DI"" LII DIYill-Envir­onmentll factors may behaving adverse effects onreproductive health.

demiological evidence suppotting a directrole of sunlight in skin cancer. The evi­dence suggests that intermittent exposuresare important in melanoma, whereascumulative or occupational exposures aremore closely related to nonmelanoma skincancer.

Also of serious concern regarding therising incidence rates of skin cancers is thedeplerion of rhe ozone layer. caused byman-made chlorofluorocarbons (CFCs).Although their manufacrure and importinto the United Srates will be illegal inJanuary 1996. these extraordinarily inertchemicals have been used in numerouscommercial products. such as aerosols andrefrigerants. According to Steingraber. theris.e of refrigeration. made possible byCFCs, resulred in a srrange twist of fate:healthier eating habits and lower rates ofstomach cancer. coupled with ozonedesrruction and its accompanying rise inmelanoma and nonmelanoma skin cancers.

"Thanks to refrigeration. we are able toeat fresh fruirs and vegetables. and foodsthat aren'r P.'eserved with nitrites. or bysmoking. pickling. or salting," Steingrabersays. ·We've reduced our exposure to thesetoxic substances that were commonly usedto preserve food 50 ro 100 years ago. andthese changes may be behind the recentdecline in stomach cancer. Ironically. rheunforeseen consequence is a potenrial epi­demic ofskin cancer."

In a May 1989 risk assessment docu­ment. the EPA prediaed that without con­trols on CFC produaion. a 40% depletionof ozone would occur by the year 2075.The agency further concluded rhar forevery I% decrease in owne. there will be a2% increase in the more damaging UV-Bwavelengths reaching the eatth's surface.Such an increase in UV-B penetration ispredicted ro result in an additional 1-3%

en increase per year in non­~ melanoma skin cancer.

While there is srrong evi·dence thar radiation fromsources such as radiotherapycan increase the risk oftumors of the nervous sys­tem. the picrure is less clearconcerning risks posed bylow doses of ionizing radia­tion or EMFs. Characterizedas nonionizing radiation,EMFs are emirted fromdevices such as power lines.transmitters. and commonhousehold items such as tele­

visions, clocks. computers. electric blan­kets. and microwave ovens.

More than a decade ago. epidemiologi­cal studies suggested that exposure to elec­tromagnetic fields (EMFs) in occupational

.~ cially data on vIctims of~ nuclear bombs in Hiroshima~ and Nagasaki.~ Additional information has~ been gleaned from studies onZ the healrh e/fects of radon in

uranium miners. Radon isfound outdoors and in alldwellings as a result of rhe

~ decay of uranium. Radon's~ carcinogeniciry is attributable

chiefly to its shorr-lived.radioactive. alpha-emittingdaughters. polonium-218 andpolonium-214. Radon eman­

ates as a toxic gas from the soil and frombuilding materials of terresrrial origin. suchas stone, bricks, and concrete.

As reponed by Jonathan M. Samet andcolleagues in the Augusr 1991 issue of theJournal oftht Ammcan MtdicalAssociation.epidemiological studies iniriared in the1950s and later. provide convincing evi­dence that radon causes lung cancer inminers. By the mid-1980s. it was widelyrecognized that radon was present inhomes and other dwellings. sometimesreaching concentrations comparable 10 lev­els in uranium mines. When ventilation isresuicted, radon may accumulate in con­centrations subsrantially higher than thoseprevailing outdoors.

Studies oflung cancer tisk from indoorradoll exposures are inconclusive. accord­ing to Radon and Lung Canm Risk: AJointAnalysis of II Undnground Mincrs Studics,a collaborative e/fon involving scientistsfrom allover the world. published in 1994.Nonetheless. based on evidence gatheredfrom studies of miners. the NCI has esti­mated that residential radon may cause asmany as 15.000 deaths from lung cancer inthe United States annually (see EHP vol.103. no. 10). This estimate includes lungcancers ascribed to radon expo­sure alone and those attributed toa combination of radon exposureand smoking. Available dara sug­gest that the risk of lung cancerfrom exposure to radon andsmoking are at least additive. ifnot multiplicative.

According to the NCI. skincancer is the most common typeof cancer in the United States.Current estimates suggest that40-50% of Americans who liveto age 65 will have skin cancer atleast once.

Ultraviolet (UV) radiationfrom sunlight is the major cause of skincancers. including malignant melanoma.Artificial sources of UV radiation. such assunlamps and tanning booths. can alsocause skin cancer. There is extensive epi-

tional exposutes. Vatioushealth e/fects have also beenteponed in experimental ani­mals adminisrered cadmiumby injection. ingesrion. andinhalation. The idea that cad­mium might cause cancer inhumans was raised in 1967when four men who hadworked in a factory makingnickel-cadmium batteriesdied of prostate cancer.Although the information onthe carcinogeniciry of cadmi­um is incomplete. epidemio-logical studies during the last few yearshave provided limher suppon that cadmi­um is carcinogenic 10 the lung. bur not tothe prosrate.

In 1987. !ARC. in its Monograph onlht EvalUlltiom ofCarcinogmicity. tevieweda number of epidemiological studies onoccupational exposure 10 cadmium andlung and prosratic cancer and concludedthat long-term occupational exposure tocadmium may conttibute to lung cancer.Confounding exposures to arsenic. nickel.and possibly other respirarory carcino­gens. including cigarette smoking. pre­vented a more definitive conclusion.

Radioactivity. Many adverse health. e/fecrs have been observed as a result of

exposure to various forms of radiation.including ionizing, ultraviolet. and electro­magnetic. Exposure to high levels of radia­tion can increase the risk of developingcancer. though a radiation-induced canceris often indistinguishable from cancercaused by other faaors. making it very dif·ficult to pinpoint radiation as the cause ofcancer.

The cancer risk associated with expo­sure to high levels of ionizing radiation isamong the best understood ofany relation­ship involving environmental agents andcancer. X.rays, gamma rays, radioactivematerials in rocks and soil. radioaaive iso­topes. and coal burning are all examples ofionizing radiation.

A National Insritutes of Health FactSheet published in 1994 cites historicaldata on the implications of human expo­sure 10 radiation. The adverse e/fects ofhigh doses of radiation were seen shortlyafter the discovery of radioactiviry in the1890s. In 1902. skin cancers were reportedin scientists studying radioaaiviry. A 1931report described cases of bone cancer inwomen who wet their brushes on theirtongues to get a good ·point" for paintingradium on warch dials. The role of radia­tion in human leukemia was first reponedin 1944 in physicians and radiologists. Thecarcinogenic potential of X-rays was con­firmed through epidemiological dara. espe-

Environmental Health Perspectives. Volume 103, Number II, November 1995 1003

Focus' The Cancer Conundrum

and residential environments might causecancer. Reports have indicated associationsbetween exposures to low-frequency(50-60 Hertz) fields and rare cancers,principally leukemia, and to cancers thatare currently incteasing in the U.S. popula­tion, including brain and breast cancer.

Acute lymphocytic leukemia (ALL),which accounts for 85% of all childhoodleukemias in the United States, has beenlinked to EMF exposure. A collaborativestudy between NCI and the Children'sCancer Group, headquartered at rheUniversity of California at Pasadena, isbeing conducted ro evaluate the risk ofALL associated with a wide range of fac­tors, including EMF exposure. Data fromthe srudy will be used to estimate theamount of prenatal and lifetime EMFexposure. EMFs have also been linked tocancers of the nervous system and brain.Evidence on the carcinogenicity of EMFshas thus far been inconsistent, but thepotential health hazards of EMF exposureremain an active area of cancer research.

Investigators at'the University of North

Carolina at Chapel Hill's School of PublicHealth recently assessed the relationshipberween EMFs and breast cancer mortalityin female electrical workers in the UnitedStates. Their findings, published in theJune 1994 issue of iNCl, indicated thatwomen in electrical occupations have anearly 40% higher mortality risk frombreast cancer than women in the laborforce withom occupational exposure to

strong electric or magnetic fields. Thoughresearchers at NCI disputed those findings,David Savitz, a professor of epidemiologyin the School of Public Health at UNC,and a member of the investigation team,says that the increasing incidence of breastcancet is justification for addressing thehypothesis. "Given the numbers affectedand how little we actually know aboutbreast cancer, at least in terms of ways thatwe can prevent ir, we need to be prettyopen minded about what might be goingon here," says Savitz.

Breast cancer is the most frequentlydiagnosed cancer in women in the UnitedStates roday. As pointed out in the SEER

Cancer Statistics R,vi,w 1973-1991, thegradual, long-term increase in breast cancerincidence seen over the past few decades isdifficult ro explain. With the worldwideannual incidence of breast cancer casesexpected to reach one million by the endof this century, a causal relationshipbetween EMFs and breast cancer wouldhave broad implications.

In light of the facr that overall cancerincidence rates are rising, most for reasonsthat are unclear, Savitz's advice CO remainopen minded is s<lund. It seems apparentthat lifestyle choices can either protectagainst or promote the onset of cancer.There is also ample evidence illuminatingthe role that exposure to various naturaland man-made environmemal substancesplay in cancer. Ultimately, elucidating thecause of cancer and protecting peopleagainsr its encroaching shadow will entailvigilant research and clarification of theinterplay of environmental and geneticfactors.

KateCahow

1004 Volume 103, Number 11, November 1995. Environmental Health Perspectives

1996 Keystone Symposiaon Molecular and Cellular Biology

Arrk9w'~!RJIdline: Seoc 20, 1995

lntegrinIland SigDaIiJIll EVeaD in Cell Biologyand DiJeutOrganizers: David A Cheresh andMartin A SchwartzMolecular and ~1opmmtaI Biology of theExtraceDular MatrixOrganizers: Benoit de Crombrugghe,Ciayton A Buck and Francesco RamirazJanuary 5-11, 1996; Keystone, Colorado

SOlOn GTP-binding Proteins and GrowthFactor Signaling PathwaysOrganizers: Gary M. Bokoch andRichard A CerioneJanuary 5-11, 1996; Tamarron, Colorado

Oxidant Smss: From Molecules to ManOrganizers: Mary E. Gerritsen, D. Neii Grangerand Guy ZimmermanJanuary 8-14,1996; Santa Fe, New Mexico

The een CycleOrganizers: Steven I. Reed andJoan RudermanJanuary 11-17, 1996; Taos, New Mexico

Blood Stem een and Bone MarrowTransplan..Organizers: Robert Peter Gale,Richard E. Champlin and James O. ArmitageJanuary 15-21,1996; Keystone, Colorado

An!bi;n/AblJaa!RJldline: Seoc 27, 1995

Mol"",lar Biology of mvOrganizers: B. Matija Peterlin and Bryan CullenJanuary 17-23, 1996; Taos, New Mexico

Hepatitis C and BeyondOrganizers: Richard H. Decker andRobert H. PurcellJanuary 23-29, 1996; Bu~ington, Vermont

r...... EngineeringOrganizers: Jeffrey A Hubbell and A HariReddiWound Repoir in ConrextOrganizers: Richard A Clark and JohnMcPhersonJanuary 23-29,1996; Taos, New Mexico

The Molecular Biology of theCardiovucular SystemOrganizers: Jeffrey M. Leiden, Victor J. Dzau,Richard Lawn, Christine Seidman,Robert Rosenberg and R. SandersWilliamsJanuary 29·February 4, 1996; Keystone, Colorado

Breast and P...late Cancer: Basic Mechanisltl5Organizers: Mina Bissell andTimothy ThompsonJanuary 29·February 4,1996; Taos, NewMexico

een PolariryOrganizers: Keiih E. MostovandPietro De CamilliFebruary 1·7, 1996; Lake Tahoe, California

AWi:aOOn!AblJaa!RJldline: O:t. 4, 1995

Ion Channels as Therapeutic Ta'1ldSOrganizers: Michael Cahalan, K. GeorgeChandy, Doug Hanson and Alan NorthFebruary 4·10,1996; Tamarron, Colorado

Gene Therapy for Hematopoietic Stem eells inGenetic Di..... and CancerOrganizers: Stefan Karlsson, Keith Humphriesand Paul TolstoshevFebruary 4·10, 1996; Taos, New Mexico

een MigrationOrganizers: Michael P. Sheetz, Rick Horwitzand Doug LauffenburgerFebruary 4·'0, 1996; Santa Fe, New Mexico

Neural PepridesOrganizers: Richard E. Mains, James F. Batteyand RobertASteinerFebruary 8·14,1996; Lake Tahoe, California

Inductive Interactions during VertebrateEmbryogenesisOrganizers: Steven C. Pruitt, MarianneBronner·Fraser, Robert M. Grainger,Mary Mullins, Christopher V.E. Wright andRichard R. BehringerFebruary 8·14,1996; Hmon Head Island,South Carolina

Molecular Mechanisltl5 in DNA Replicationand RecombinationOrganizers: Michael O'Donnell andStephen C. WestFebruary 10·16, 1996; Taos, New Mexico

een Biology of Virus Entry, Replication andPathogenesisOrganizers: Richard W. Campans, Ari Heleniusand Michael B.A OldstoneFebruary 10-16, 1996; Santa Fe, New Mexico

AppIig!!DJIAhmct o.:.IIire Oa. 18. 1995

Molecular Rqulation of Platelet ProductionOrganizers: Martin J. Murphy, Alan M. GewirtzandSiLokThe Hematopoietic MicroenvironmentOrganizers: Armand Kealing andJoel GreenbergerFebru ary 16-22, 1996; Taos, New Mexico

Exploring and Exploiting Antibody andIg Superfamily Combining SitesOrganizers: Edgar Haber and James S. HustonFebruary 22·28, 1996; Taos, New Mexico

Molecular Helminthology:An Integrated ApproachOrganizers: James L. Bennett, Timothy G.Geary, Donald L. Riddle, Richard M. Maizels,Phiiip LoVerde and Valarie WiiliamsonFebruary 22·28, 1996; Santa Fe, New Mexico

Molecular Approaches to the Function ofIntercenular JnnctionsOrganizers: Bruce J. Nicholson, DanielGoodenough, Pamela Cowin and Peter BryantMarch 1·7, 1996; Lake Tahoe, California

Vint Genome ReplicationOrganizers: Paul Ahlquist, Jeremy Bruenn andEckard WimmerMarch 1·7, 1996; Tamarron, Colorado

Posttranscrlptional RNA ProcessingOrganizers: Kenneth Stuart, Michael Green andJack SzostakMarch 11·17, 1996; Hilton Head Island, SouthCarolina

Molecular Basis (or Drug Resistance inBacteria, Parasites and FungiOrganizers: Stuart B. Levy and Thomas E.Well8msMarch 11·17, 1996; Pari< City, Utah

The Extracenular Matrix of P.....:Molecular, eenular andDevelopmental BiologyOrganizers: Andrew Staehelin, Michael Hahn,Norman Lewis, Andrew Mort and Keith RobertsMarch 15·21, 1996; Tamarron, Colorado

AppIiglJin/Almactllildlre Nov. 15, 1995

Steroid/Thyroid/Retinoic Acid Gene FamilyOrganizers: Kathryn B. Horwitz, John ACidlowski and Ronald EvansMarch 17-23, 1996; Lake Tahoe, California

Transcriptional MechanismsOrganizers: Thomas Shenk andDanny ReinbergMarch 17·23, 1996; Taos, New Mexico

Lymphocyte ActivationOrganizers: Susan L. Swain, B.J. Fowlkesand John CambierMarch 20-26, 1996; Hilton Head Island, SouthCarolina

Proteolytic Enzymes and Inhibiton in Biologyand MedicineOrganizers: James Travis, Clarence A Ryan,Hidsaki Nagase and Chrisline DebouckMarch 25·31, 1996; Keystone, Colorado

Immunopathogenesis of mv InfectionOrganizers: Robert Schooley, Bruce D. Walkerand Denis HenrardMarch 26-Aprill, 1996; Hilton Head Island, S.Carolina

Signal Transduetion through Tyrnoine KinasesOrganizers: Ralph A Bradshaw, Lena Classen·Welsh, David Kaplan, Unda Pike and KlausSeedorfSignaling in Neuronal Development,Differentiation and DegenerationOrganizers: Mariano Barbacid, MichaelGreenberg, Ronald McKay andGeorge YancopoulosMarch 27-ApriI2, 1996; Taos, New Mexico

The Conduct of Science: Keeping the FaithOrganizers: John Bailer, Jeff WilliamsMay 2·5,1996; Keystone, Colorado

•Regi:;traOOn in any~ in a shad<xI groop quaIifesfor attendaoce in any~ in d-ot groop.

For more in[omll1/im, please aJI1UICt::

Rme (970) 262-12.30K~Sym(XNl, DrnwerI630, SMrtInne,(X)!008Fax: (970) 262-1525 Email:sym(Xli2@~

Collection CostsA major porrion of rhe cosr ro communi­ties of recycling is the cosr of collectingrecycled goods. It's these cosrs, argue crit­ics, that can make recycling a bad bargain.

"What happens in recycling is rhat col­lection cosrs are very high and the collec­tion is done separately from trash collec­tion, and so that's what drives the dysec­onomies of recycling," says KennethChilton, direcror of the Center for theStudy of American Business, a rhink tankin St. Louis, Missouri. Collection cosrs forrecyclables are approximately equal ro rhatofcollecting ttash at around $50 per ron.

One example of this problem is the cityof San Jose, California, which reports itcosrs $28 per ton to landfill wasre com­pared with $147 a ron to recycle.According ro Lindsey Wolf, rhe city's man­ager of government relations, rhe $147 per(On is an "incentive fee" paid to the privatecompanies that colleer rhe recyclables andmarket them. "They take all the risk andget all rhe reward," she says, noting thatthe city gers no money for the recycledmaterial collected. But the city does getsome rewards, she says. As a result of recy­cling, the ciry has extended the life of irslandfill by four years, says Wolf.

In Arlanric County, New Jersey, for thefirst six monrhs of 1995, recycling broughtin $2.45 million, says James Rurala, vicepresidenr of the counry's public utilitiesauthoriry. But the cosr of collecting the

als, whether virgin or recycled, was low.Prices for recycled materials plummeted.The aggregate value for a ton of recycledmaterials in 1988 was $60. In 1991 and1992, rhis same ron brought $15.

Bur in the last few years, Scarlett says,rhere has been a sea change in recyclingeconomics, with prices dramaticallyrebounding. Still, the economics of recy­cling is a mosaic of issues including collec­tion cosrs, market demand, landfill cosrs,and recycling infrastructure and technolo­gy. Determining whether recycling makeseconomic sense involves analyzing thesecomponenrs ro see how rhey fit inro thetotal picture.

Cycle of RecyclingThough recycling may seem like a recenrinnovation because of the media attentionit has received in the last decade, forms ofrecycling have been in use in the UnitedStates for almosr 100 years. At the turn ofthe century, wasre paper and tags wereused ro make new paper when wood pulpwas scarce or too expensive. Recyclingsctap metal and other materials was anAmerican insritution during World WarII. And deposirs on glass soda botrles in the1950s and 1960s encouraged people torecycle and reuse rhem.

When the mote modern version ofrecycling began, irs economics were disas­trous in some cases, according to LynnScarlett, vice presidenr for research of theReason Foundation, a Long Beach, Cali­fornia, nonprofit think tank. In somecities, it cosr about $400 per ron ro colleer

" recyclables in 1990 and 1991.t In Chicago, rhe cosr of an ini­i tial cutbside recycling project~ was $1,000 a ton, says Scarlerr,~ which made it unfeasible. It.3 cosr around $70 per ron to

dump refuse inro landfills atrhat time.

Moreover, when recyclingbecame popular, the counrrywas in an economic slump. In1991, in rhe middle ofa reces­sion, the demand for materi-

rional rrucks ro pick uprecyc1ables increases roxicdiesel emissions, offsettingany environmental gains.

Recycling advocares arequick ro respond rhar eco­nomics are not the only

considerarion and rhar recycling is essenrialin managing America's solid wasre. Theysay rhar using recycled insread of virginmarerials benefirs rhe environmenr by cur­ting back on a wide range of polluranrs andpreserving biodiversity. And, they add,recycling may make economic sense bydelaying or lessening rhe need for landfillsso that land can be put to more productiveuses.

RethinkingRecycling

Americans seem ro be having a love affairwirh recycling. No longer do people simplylook for a refuse conrainer ro ross away aused soda can or plasric borrle. They searchfor rhe righr recycling recepracle. Alloverrhe Unired Srares, when ir's rime ro rakeour rhe garbage, millions of people rakeour carefully sorred bundles of newspapersand cardboard, bags of aluminum and sreelcans, and plasric conrainers-all desrinedfor recycling.

According ro BioCycle magazine'sannual survey, rhe Unired Srares had 7,265curbside recycling programs serving 108million people lasr year. Furrhermore,every srare in rhe union has some rype ofprogram aimed ar recycling. The programsrange from diverring large amounrs of plas­rics, aluminum, paper, and cardboard fromlandfills ro sorring faciliries, which sendthem on their way to be reused in manu­facrure, ro simply having srare govern­menrs buy producrs conraining recycledmarerials. "lr's become a way of life," saysDonald Berman, direcror of solid wasremanagemenr for Allegheny Counry,Pennsylvania, which includes Pirrsburgh.

Bur is ir a way of life rhar makes eco­nomic and environmenral sense? Recenrlya number of economisrs and policy ana­lysrs have quesrioned wherher rhe benefirsof recycling ourweigh rhe ease of disposingof wasre marerials in landfills.Crirics say rhar whar seems arfirsr ro make a grear deal ofsense doesn'r always srand upto a close examination. Forinstance, some critics arguerhar collecrion cosrs makerecycling a bad bargain formany localiries because rhecosrs ofren exceed rhe pricesrhar rhe recyclables bring onrhe open marker. They alsocharge rhar operaring addi-

1006 Volume 103, Number 11, November 1995· Environmental Health Perspectives

t-OCUS • HetnlnKlnfl HeCYCllng

Lynn Seorlott-In many situ­ations recycling is a conun­drum.

recycled goods came ro $1.6 million, andsorring the recycled matetials cost $1.1million plus the $325,000 in interest pay­ment on the recycling facility. Con­sequently, recycling accually cost the coun­ty over half a million dollars.

But Rutala doesn't think this provesthere are no benefits from recycling. "Ithink it's definitely worrh it," he says,because approximately 20% of the coun­ty's waste stream is recycled.

Limiting LandfillsAlthough collection costs may be on thelist of cons for recycling, adding the cost oflandfills swings the balance back towardthe pros. Rutala says that the cost per tonof landfill space, added to collection costs,can average as much as $88 per ton. "Youpay $88 a ron ro put that material in theground," he says. 'There are no positivesthat are being derived from that." Rutalaadds that recycling lengthens the life of theexisting landfill. Siting a landfill can costmillions of dollars. Recycling, Rutala says,has taken the issue oflandfill siting "off thelocal agenda."

In Madison, Wisconsin, recycling hasmeant notable savings, accotding toresearch done by John Reindl, the recy­cling manager for Dane County. Madisonrecycles about 50% of its householdwastes. Reindl found that in the past yearrecycling has saved the city over $500,000in landfill chatges and has earned$475,000 for the city from the recycledproducts. "They saved over a million bucksby going to recycling," he says. Other citiescan make similar savings. but it requiresattention ro operations and looking forways to become more efficient.

Berman notes that landfill prices havedecreased over the past several yeats. Onereason is simple supply and demand. Landfil1

prices in the Alleghany Countyarea climbed in the late 1980s."A number of companies gotinro the business. There's morelandfill space than we hadbefore, but there isn't that muchmore material than we hadbefore, so prices have gonedown," he says.

Nevertheless, Berman arguesthat recycling is worrhwhile."The cheaper the landfill, theharder it is to make a profitwith recycling, no questionabout it," he says. "No one isgoing to balance budgets with recycling, butit is a very affordable teaching tool."

Local situations have ro be taken intoaccount when figuring the cost of recyclingvetsus landfill disposal, argues RobertStavins, associate professot of public policyat the JFK School of Government atHarvard University. "Ifwe're talking aboutNevada, which has low costs for siting alandfill, it's a relatively cheap alternative. Ifwe're talking abur Rhode Island, it's acompletely different story. So it's impossi­ble in my opinion to generalize nationwideabout whether recycling is a desirableapproach. It's going ro vary from commu­nity to community."

But Richard Dennison, a senior scien­tist with the Environmental Defense Fund,argues that direct economic benefit tolocalities is not the only way to measurethe economic benefits of recycling. "Thereare enormous economic savings elsewherein the system that may not acccue to thelocal solid waste manager," he says, refer­ring for example to the energy savings thatcan be made by using recycled instead ofvirgin materials. One step that can betaken, Dennison says, is simply bargainingfor berter prices for recycled goods-taking

~ advantage of the higher prices~ that industries now are pay~

j ing for many recycled com­! modities.~

Recycling Market"The majority of materialprices [for recyclables] arenoticeably berter than threeor four years ago," says MaryKohrell, a recycling marketsspecialist for the University ofWisconsin Extension. Sales ofrecycled goods can dramati-cally offset the COStS of recy­

cling, but the market for such goods varieswidely depending on the availability of vir­gin goods, environmental regulations, andthe costs of using such materials.

"Paper in 1995 has been astronomical.Prices have been higher than ever," Kohrellsays, citing prices of $100-$200 per ron.JUSt three years ago, she says, paper was sell·ing for $10-$15 per ton.

Kohrell points out other prices indicat­ing a healthy market for recycled materials.Plastics, she says, are selling for between$200 and $300 per ron as of July. Twoyears ago prices were less than half of that.Aluminum is selling for between $840 and$1,060 a ton. Only a couple of years ago,she says, the price was between $640 and$740 per ton.

But the high prices for recycled materialsdon't impress Lester Lave, professor of ec0­

nomics at the Graduate School of IndustrialAdministration at Carnegie MellonUniversity, who questions the economicworth of recycling. "Ifone takes a look at thepast record [of prices), the notion that it'salways upward from here is kind of crazy,"he says. "[ think the one thing that I feel rea­sonably certain about is that the prices wesee now are not going to prevail in the

Generation of municipal solid Wist,Recovery and discards of residantialand commercial

municipal solid waste

~

200

I 1SOSc

:E lOll·s

so

1992

_ Recyclable products_ Vardtrinvnings

2lIOO

_ Other compostable/combustibles_Othermaterials

,so

200

. ISOcSc

:5 lOll·s

SO

1992

_ Recovered commercial_ Unrecovered commercial

2lIOO

Recovered residential_ Unrecovered residential

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1007

Focus' Rethinking Recycling

Energv Usage and EnVironmental EmiSSions 1per 1011 of material recycledl

MaterialsRecovery Residue Avoided

Recyclables Facility Landfill Transportation Energy andCollection Process Disposal to Market EmissionsB Total

Net Energy Usege 989.0 282.7 42.2 212.6 118,326.51 116,800.0)(1b.....dS..)

Envi......1IllI1 Emissi... (p.u.ds)

Atmospheric EmissionsAldehydes 0.0356 0.0002 0.0015 0.0076 10.55831 10.51341Ammonia 0.0002 0.0002 0.0000 0.0000 10.00801 (0.0076)Carbon dioxide 157.7 31.7 6.7 34.2 12.724.61 12,494.21Carbon monoxide 1.8300 0.0413 0.0781 0.2640 (27.4) 12521Chlorine 0.0000 0.0000 0.0000 0.0000 10.04521 10.04521Hydrocarbons 0.7260 0.0726 0.0310 0.1438 17.71 16.81Hydrogen fluoride 0.0000 0.0000 0.0000 0.0000 10.17661 10.17661Lead 0.0000 0.0000 0.0000 0.0000 10.00621 10.0062Methane 0.0004 0.0002 0.0000 0.0000 10.01061 10.01001Nitrogen oxides 1.9152 0.1746 0.0817 0.2898 111.9) 19.4)Other organics 1.1176 0.0002 0.0477 0.1336 11.57211 10.27301Particulates 0.4256 0.1060 0.0182 0.0482 111.91 111.31Sulfur oxides 0.2700 0.2861 0.0115 0.0582 111.51 110.9)

Solid Wastes 0.4944 163.8 0.0211 0.1066 1996.21 1831.8)

Waterborne WastesAcid 0.0000 0.0228 0.0000 0.0000 10.46441 10.44161Ammonia 0.0000 0.0000 0.0000 0.0000 10.09441 10.09441Biological 0, demand 0.0006 0.0002 0.0000 0.0002 10.53861 10.53761Chemical 0, demand 0.0030 0.0005 0.0001 0.0006 11.49001 11.4858)Cyanide 0.0000 0.0000 0.0000 0.0000 10.00381 10.0038)Dissolved solids 0.6120 0.0852 0.0261 0.1320 16.21 15.41Fluorides 0.0000 0.0000 0.0000 0.0000 10.10401 10.1040)Iron 0.0004 0.0170 0.0000 0.0000 10.09521 10.0778)Metal ion 0.0010 0.0058 0.0000 0.0002 10.21241 10.2054)Oil 0.0074 0.0001 0.0003 0.0016 10.05301 10.0436)Phenol 0.0000 0.0000 0.0000 0.0000 10.00241 10.0024)Sulfuric acid 0.0018 0.0005 0.0001 0.0004 10.00421 10.0014)Suspended solids 0.0006 0.0000 0.0000 0.0002 12.5) 12.5)

Values in parentheses represent energy and environmental emissions avoided due to increased use ofrecyclable materials in the remanufacturing process.• Based on the following mix Iby weight) of recyclable materials: 50% paper, 32% glass, 8% steel, 4%aluminum, 4% HOPE, 2% PET.

Mer, Kohrell-The infra­structure for recycling hasmatured.

from individual to individual. Still, advo­cates of recycling argue that the moreinrangible benefits offer the mosr com­pelling case for recycling.

Curting down on energy used to manu­facrure wirh virgin materials means cuttingdown on pollutanrs like carbon monoxide,nitrogen and sulfur oxides, and volatileorganics, according to a report publishedby Keep America Beautiful, Inc. Recyclingadvocates argue rhat recycling curs downon rhe amounr of dioxin released inro rheenvironmenr from bleaching of virgin pulp,for example.

Recycling paper also saves trees. Treesreduce rhe amount of carbon dioxide pre­sent in the environment mar conuibutes toglobal warming. According ro Kenneth

Environmental GainsThe economic issues sur­rounding recycling may seemcomplex, but rhey are at leastsomewhat quantifiable. Thehealth and environmentalbenefirs of recycling, includ­ing energy conservation, toxicemissions reductions, andpreservation of resources, arefar more difficulr to quanti/Y.Health and environmentalbenefits are somewhat indi­rect and are valued differendy

bankrupt all the time, jusr because theyhave overly optimisric expectations aboutwhat prices will be," he says.

future, rhar we're going ro see cyclic pricesgoing up and down. . .. An overwhelmingbet is char rhe long-renn rrend is going ro bedownward, nor upward."

Bur orhers see a differenr picture. WhileKohrell and Scarlen acknowledge rharprices aren'r going to stay high forever (forinsrance, prices for recycled paper havestarted ro fall), rhey see sready markers formany recycled commodiries in rhe future.Scarlerr says, "I do nor rhink prices willdrop to rhe real doldrums. Why? We'veseen an enormous investmem in infrastruc~

rure ro use rhis sruff." Indusnies havebegun to invest great amounts of money inequipmenr and planrs to use recycled mare­rials, realizing rhar rhere will be a sreadyscream of ir in rhe furure.

Between 1988 and 1994 the papetindusrry spenr $7.5 billion in technologyand capital investmenrs to recycle paper, saysRichard Stotat, vice presidenr of economicsand materials of the Ametican Forest andPaper Association. "The industry, between1994 and the year 2000, expeers to spendsomewhete around $10 billion on additionaltecycling capacity," Storat says. The goal isto recycle approximatdy half rhe paper usedin rhe United States.

Paper is not rhe only industry rhat hasgeared up for tecycling. "The infrasttucturethat assures that plastics get recycled hasreally matured over the pasr five years interms of the actual capacity ro processmaterials," says Kohrell. Makers of plasticcontainers are putting increasing amountsof recycled materials in conrainers, saysScarlerr. For example, Procter & Gamble,which makes a multitude of householdproduces, uses from 25% to 100% recycledplastic to make irs containers. "When youhave a Procter & Gamble with millionsand millions of bonles produced each year,it means an enormous and continuousdemand,' Scarlerr says.

But it's almosr cenain there will beswings in demand and consequenr swingsin prices. For example, earlier rhis year acotton crop failure in China boosred plasticprices because recycled plastic can beturned into polyesrer fiber toreplace corron fabric. "TheAsian markers began massivelyimporting recycled plasrics."Scarlert says. Bur in June, alarge number of Asian virginplastic planrs began operating."So rhe Asian market [for recy­cled plastics] kind of wentbust. The prices started rodrop,' she says.

Lave says rhar such exam­ples support rhe need for cau­tion: "There are firms rhat go

1008 Volume 103, Number 11, November 1995 • Environmental Health Perspectives

Focus' Rethinking Recycling

Lindl Glines-Recyclingmay not always be theanswer.

Dlvid Sobers-Recyclingdecisions must includeanalysis of local conditions.

Generation Recovery

Total Total %

Organic productsNewspapers 12,550 5,470 44Corrugated 25,400 13,395 53containers

Office papers 6,680 2,370 35Magazines, 5,180 915 18similar products

Mixed papers 17,555 2,340 13PET bottles 760 225 30HOPE bottles 1,215 180 15Other rigid plastic 1,500 22 1containers

Plastic film 3,500 85 2Other plastics 950 30 3Polypropylene 70 62 89battery casings

Textiles 5,140 256 5Tires (rubber only) 2,820 500 18Wood pallets 8,935 2,235 25

Inorganic productsSteel cans 2,817 1,135 40Major appliances 2,665 1,455 55(ferrous metals only)

Aluminum cans 1,584 1,075 68Other aluminum 361 30 8packaging

Glass containers 11,890 3,900 33Automotive batteries 751 740 98(lead)

Yard trimmings 35,000 6,000 17

MUniCipal Solid Waste Generation. Recovery.and DIScards 1992

Recovery in this table is for recycling and com­posting only.

Harvey Black

Arriving at a broad understanding ofthe economic and environmental impactsof recycling compared with using virginmaterials-a so-called life cycle analysis-isevolving. Susan Thornloe, a research engi­neer at the EPA, heads a three-year studyaimed at providing definitive answers."What we're in the process of doing isidentifying where information exists andwhere data gaps are," she says. Right now,Thornloe says, the picrure is incomplete, ifnot misleading. "What we're trying to do issomething that is scientifically dtiven andis objective,II she says.

The debate over recycling's economicand environmental impact is certain tocontinue. For all its superficial simpliciry­for most people simply sorring recyclableitems into the proper container to be col­lected-recycling involves a host of com­plex questions. Nevetrheless, tecyclingseems to be here to stay, as society, includ­ing both households and manufacturers,adapts to accomodate the issues of recy­cling and looks beyond the curbside at itslasting effects.

The analytical and environmental thick­et that paper presents isn't unique. Scarlerrpoints to glass recycling as another instancein which "devilish details" have to be con­sidered when viewing the costs and benefits

~ of recycling. Generally, she~ says, recycling glass rakes less~ energy than making virgini glass, meaning reduced~ emissions of gases such as~ carbon monoxide. The type

~ of furnace used in glassmak­ing, however, alters thatgenerality. Scarlerr points tothe use of cleaner-operatingelectric furnaces to replacetraditional furnaces poweredby fossil fuels. Althoughthey use less energy and thuscreate less emissions than

natural gas-powered furnaces, electric fur­naces cannot use as much recycled glass, sothey are nor as efficient. The consequence isa "conundrum," says Scarlen.

The Keep America Beautiful study alsoqualifies its conclusions about the environ­mental advantages of manufacturing withrecycled instead ofvirgin material. "It is pos­sible that the total energy requirements ass0­

ciated with increased recycling could begreater than manulacruring with virgin rawmaterials. For example, shipping recoveredmaterials extremely long distances to endmarkets may negate any energy savings real­ized in the manulacruring process."

Coupled with these issues is the prob­lem of resolving how much material shouldbe recycled. Reid Lifset, associate directorat the Yale Program on Solid Waste Policy,argues that a 50% recycling goal is eco­nomically and technically feasible. AndStorat says the paper industry's goal is torecover and recycle half of all the paperused in the United States by the year 2000.

But serring such goals has to be donecarefully, according to David Sobers, vicepresident and national practice manager forsolid waste with Woodward-Clyde, an envi­ronmental consulting firm. Taking a recy-

cling goal that is effective ini one locality and trying to

~ impose it on a wider area may~ not work, Sobers maintains.~ Market conditions, transporta-

tion systems, even the purityof the recycled material canvary /Tom one area ro another.If goals are set without carefulanalysis of the local condi­tions, "one can overregulateand cause greater environmen­tal emissions and cosrs ll thandisposal in a properly engi­neered landfill, he argues.

Skog, a researcher ar the U.S. Forest Pro­ducts Laboratory in Madison, Wisconsin,"The cumularive effecr is noriceable."Skog estimates thar recycling paper insteadofcurring down trees can add an additional12-13 million metric tons tothe 100-200 million metrictons of carbon dioxide stored inforesrs each year, depending onthe amount of paper recycled."1r's a norable addirion to rhebenefits of recycling," he says.

The federal governmenr'sClimare Change Action Planincludes paper recycling as oneway to cut down on greenhousegases, bur the issue may be morecomplex than ir first appears.Recycling newsprint is a goodidea, says Linda Gaines, a sys­tems analyst at Argonne National Labora­tory. "Newsprint is a clear winner. Ir doestake more fossil fuels to make newsprintfrom trees rhan from recycled paper. Ir'sharder ro crunch up a tree rhan an oldnewspaper," she says.

But when it comes to recycling officepaper, the situation is differenr. Whenmaking office paper from trees. a renew­able resource is used; when recycling thatpaper, a fossil fuel is being depleted. Whensuch paper is made from trees, part of theprocess is fueled by wood by-products ofthe pulping process. "When you recyclethat paper there is no by-product fuel, soall of the fuel need is purchased fossil fuel,"says Gaines.

Instead of recycling office paper,Gaines says, it should be used to generateenergy in coal-fired power plants. "Thenyou burn less coal and displace some of thecoal emissions. Paper is a really good, cleanfuel," she says.

"If you're looking at greenhouse gases,"says Gaines, "if what you're doing is burn­ing biomass and replanting it, there's nonct greenhouse gas increase from thatcycle. But if you're burning fossil fuelthere's an increase in greenhouse gases,"Thus, she argues, recycling hasto be done in lighr of the goalsthat society wants to achieve.

Bur Dennison argues thatGaines' analysis glosses over animportant facror. "The woodhas to be harvested from a forestand the forest has to be managedto produce the wood. And thatset of management practices hasimportant environmental conse­quences with regard to biodiver­siry, habitat, and so forth, thathave to be counted as debits onthe virgin side of the ledger."

Environmental Health Perspectives' Volume 103, Number 11, November 1995 1009

Spheres of Influence 'What Cost Health?

commitment to science quality. and theuse of peer review for all ORO research(which includes studying pesticide expo­sure in children and the effect of chemicalson the endocrine glands) are also genetat­ing congressional support.

An EPA official who asked not to beidentified said criticism of how the EPAuses science may stem from the researchdone by EPA program offices that is usedto suPPOrt rules under specific regulatoryprograms. like the Clean Air Act or theSafe Drinking Water Act. To address qual­ity concerns, EPA Administlator CarolBrowner has asked program offices toadopt srandard operating procedures forpeer review of all research. The emphasison peer review "is one of the culturalchanges occurring in rhe agency." thesource said.

Although the House approved increas­es for the EPA's research and developmentaccount. it approved curs of $457 millionfor personnel costs and compliance andmonitoring activities. An EPA source saida dramatic cutback in funding for person­nel costs could mean some EPA labs mighthave ro be closed. The seeming contradic­tion in the House's decision to provideincreases for EPA research and develop­ment but not the staff to do the work wasaddressed by Alan Moghissi. director of theInstitute for Regulatory Science and a for­mer EPA researcher. Moghissi suggestedthat House appropriators may have intend­ed the EPA to contlaet out more research.a strategy he thinks might produce minorbenefits. But twO EPA sources said there isno evidence to support such speculation;one source noted that Congress last yearapproved additional staff to ensure thatwork would not have to be contracted out.

While the EPA ponders the meaning ofthe House's budget numbers, LindaRosenstock, director of NIOSH believesher agency's budget numbers from theHouse have a clear meaning: the first stepin possible elimination. The Houseapproved a $99 million budget for FY1996, which is 25% less than NIOSHreceived in FY 1995. Cuts of that sizewould be devastating to NIOSH's intra­mural and extramural programs,Rosenstock said, and would affect publichealth, not just workplace safery. "All ofOUf research activities have a connection to

the public." she said, citing NIOSH'sresearch on occupationally related cancersand asrhma. "Our knowledge about wharcauses asthma in the workplace is verytransferrable ro concerns about rising asth­ma mortality and morbidity that may alsobe relared to environmental exposures."

The public benefits from NIOSH

research because the public is oftenexposed to the same hazardous substancesfound in the workplace, as workers carryhome to their families hazardous sub­stances like lead. or as substances are emit­red from workplaces into the atmosphere.But Rosenstock believes the public healthbenefits provided by NIOSH go unnoticedby some members of Congress, whobelieve the institute's activities are dupli­cated by other agencies. For these reasons,Rosenstock said. last summer's budgetnumbers may be a first step toward elimi­nating NIOSH. And eliminating NIOSH,she said. would contladict rhe desireexpressed by some in Congress forimproved science. A congressional sourceagreed wirh Rosenstock that House appro­priators may have been unclear aboutNIOSH's work, bur also said the institutemay have been "lumped in with OSHA"and therefore considered deserving of siz­able cuts.

The Senate, however, may better recog­nize the value of these twO agencies. In theSenate budget, NIOSH would receive$137 million, an increase of $38 millionover House appropriations. and OSHAwould receive $296 million. whichalthough an almost $16 million cut fromthe FY 95 budget, would still be $22 mil­lion more than the House appropriations.

Congressional budget-cutters also axedfunding for DOE programs ro assess work­er healrh and safety and the health of com­munities near DOE faciliries. Congressapproved a $5 million recision in an FY1995 budget of $18 million for a programto study populations around contaminaredDOE fuciliries. "We're trying to minimizethe disruptions to on going studies," suchas dose reconstruction studies and the thy­roid disease study of communities aroundHanford, said Mary Jo Zacchero, assistantto Tara O'Toole, DOE assistant secreratyfor environment, safety, and health. "It'sclear that there will be less [money] thanwe thought we would have."

NonheaIth Environmental ResearchCongressional appropriators were even lessgenerous with environmental research notdirectly relared to health, according toPetet Backlund, a staff member of theCommittee on Environmental and NaturalResoutces. a subcommittee of the intera­gency National Science and TechnologyCouncil which operates from the WhiteHouse Office of Science and TechnologyPolicy. The EPA's Environmental Tech­nology Program. global change research bythe Narional Aeronautics and SpaceAdministration and the DOE, and theDOE's solar and renewable energy research

programs have been targeted for cutS,Backlund said. which the Clinton adminis­tlation believes will hinder effom toimprove scientific knowledge about envi­ronmental issues. But budger cuts are likelyto recur, Backlund said, and agencies willhave to constantly assess the efficiency oftheir programs and eliminate duplication,which are key objectives of the NationalScience and Technology Council.

The National Association of Manu­facturers' Cohen believes improvements inefficiency will help federal agencies. likeprivate businesses, accomplish more inspite of less funding. The private sector hascoped with strained resources and learnedhow to operate more efficiently, Cohencommented, and government will have todo likewise. "We don't accept the premisethat the only way government and EPA inparticular can do more is by throwingmore money at the agency." he said."Government can do things berter andsmarter."

Still. the size of the cutS advocated bythe House last summer for the EPA andOSHA was "totally without precedent,"according to Vice President Gore, andenvironmental groups, labor unions, andthe affected agencies offered dire predic­tions about the consequences of such cuts.EPA Administrator Browner told reporterslast summer that the House's proposed50% reduction in the Clinton administra­tion's request for enforcement activitieswould cripple the criminal enforcementprogram, under which 525 criminal caseswere brought in 1994. Browner said fund­ing would be eliminated for local govern­ments to improve drinking water systems,and no new cleanups would occur underthe Superfund.

OSHA estimated that reduced fundingwould cause an additional 50,000 work­place injuries, and Keith Mestrich, anoccupational safety and health specialistwith the AFL-CIO. predicted more haz­ardous releases into communities sur­rounding plants if OSHA's complianceactivities are severely curtailed. A strongenforcemenr program nor only identifiescompanies that don't comply. but alsodeters businesses from violating OSHArules. Mestrich said. If businesses knowthat OSHA will not be able to enforce itsrules, companies may have little incentiveto comply. he said. The DOE alsoexpressed great alarm at the House's pro­posalto cut $800 million from the depatt­ment's $6.6 billion request for irs environ­menral managemenr program, contendingthat cuts of that size would affect cleanupsof 50 DOE facilities in 20 states andwould hinder the department's ability to

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1011

Spheres of Influence· What Cost Health?

address urgent thteats like leaking andpotentially explosive underground radioac­tive waste tanks.

Sharon Buccino, staffartorney with theNarural Resources Defense Council, andKaren Fiorini, staff attorney wirh rheEnvironmenral Defense Fund, believe thesize of the House's proposed cuts, coupledwith regularory reform, are part of aneffort ro radically alter environmental poli­cy. The budget resolution approved by theHouse and Senate, Buccino noted, con­templated a 13%, across-the-board cut ingovernment programs, yet the reductionsproposed by the House for the EPA andOSHA were more than double the 13%tatget. For this reason, the House EPAbudget and its numerous riders that wouldprevent the EPA from implementing cer­tain laws reflect a desire ro reduce environ­mental protection, not simply a desire toreduce the fedetal budget, she said.

Fiorini said the budget cuts would beespecially harmful if coupled with regula­tory reform because the agencies would besaddled with increased workloads just as

resources are shrinking. Some of the regu­larory reform proposals, she said, wouldrequire agencies to conduct detailedcosr-benefit analyses of proposed regula­tions and of alternative approaches to

determine whether an alternative might bemore cose effective, leaving "the agencyswamped with more paperwork and unableto spend time enforcing new rules," shesaid. "It doesn'r marter if sociery would beberter off if the agency addressed otherproblems; industry would get first caliondwindling taxpayer resources." The impacton agency resources would hinder effortsro address increased asthma morbidiry andmortaliry and the emerging issue of envi­ronmental endocrine disrupters, Fiorinisaid. "It's unquesrionably the case that wecan have smaner more streamlined regula­tion," but, she said, the proposals are like"remodeling the kitchen by blowing it upwith a bomb."

Anemic BudgetsWalter Rosenbaum, a political science pro­fessor at the University of Florida at

Gainesville and a former policy analyst atthe EPA, doubts that the EPA couldendure cutbacks of 10-30% without majorconsequences, in part because EPA budgetswere trimmed back during the Reagan­Bush era. "What you're doing really isbleeding a patient that already has a badcase of anemia," he said, adding that thebiggest health impacts could stem from theagency's response, or lack of response, toroxic air emissions and water pollution.The Clean Air Act Amendments of 1990imposed stricter standards on toxic airemissions, which the EPA has been strug­gling to implement, Rosenbaum said, burthe program was targeted by House budgetcutters. Similarly, budget suPPOrt has beenweak for EPA efforts ro address water pol­lution from nonpoint, or diffuse sources,such as groundwater contamination frompesticides used on farm fields. "That'swhere the health impacts could be great,but it would be years or decades before itwould become known."

Karen Breslin

Volume 102, Supplement 9, November 1994

Toxicological Evaluationof Chemical Interactions

hEcMmnmen<o'Hea""e~perspectIVes

Supplements

Under the sponsorship of the International Sociery for the Study ofXenobiotics (ISSX), a satellitemeeting of the IV European ISSX meeting, "Toxicological Evaluation of Chemical Interactions:Relevance of Social, Environmental, and Occupational Facrors," was held in Bologna, Italy, July3--Q, 1992. The primary aim of the meeting was ro identifY those combined exposutes for whichsynergisric, antagonistic, or potentiating effects may still be significant at real exposure levels, con­sidetably affecting the risk for humans. Contributions covering all aspects of roxicological evalua­tions - including analytical and biological procedures to detect exposure, roxicokinetics, xenobi­otic metabolism, roxic effects, and risk assessment - were presented as invited lectures, oral com­munications. and posters.

To order your copy. write:Supplement Circulation IEnvironmental Health PerspectivesNational Institute of Environmental Health SciencesPO Box 12233Research Triangle Park, NC 27709Fax 919-541-0273.

1012 Volume 103, Number II, November 1995. Environmental Health Perspectives

Stockholm, SwedenSeptember 15-20, 1996

The Congress will be a world-wide forum to sharethe latest scientific advances within all principalfields of occupational safety and health. Theapplication of these advances in occupationalhealth practice will also be presented. Topics ofthe congress include the influence on health andwell-being of chemical and physical factors, at thework site, as well as the impact of ergonomics,psychosocial factors, work organization and newtechnology. visitors to earlier ICOH congress willrecognize the general structure of ICOH'96.

Courses

Courses on "Continuous Quality Improvement inOccupational Health Services" and "RiskAssessment of Carcinogens" will be held inStockholm, Sweden, and Helsinki, Finland, in con­junction with the congress. The courses are beingorganized by the Nordic Institute for AdvancedTraining in Occupational Health (NIVA).

Keynote addressesTopics to be reviewed in the

keynotes include:

o Dose concepts in occupa­tional health.

o Electromagnetic fields andcancer.

o Gender and work.o Occupational health in a

global perspective.o Participatory approaches in

occupational healthresearch.

o Prevention of musculoskele­tal disorders.

o Promoting safe behavior.o Working conditions and car­

diovascular disease.

For more information contact:

ICOH CongressNa60nallns6tute 01 Occupa60nal Health

5-171 84 SolnaSWEDEN

FAX: (46) 8 82 05 56

Innovations' In Vitro Innovations

Wide engle lens? Effects of toxic substances can be assessed bydirecting a laserbeam through a cow lens and measuring the angle ofrefraction.

also show that the small protein moleculesknown as cytokines mediate intetactionsbetween mixed cultures of keratinocytesand fibroblasts.

More complex models combine ke­ratinocytes with fibroblasts to produce adermis and epidermis with varying degreesof differentiation. Which model yields thebest information? "That depends on thequestion you are asking," explains Ponee.Rheins concurs, citing some of the differ­ent uses for Skin2

• "The ZK1000 [dermis]is typically used as a rapid screeningmethod to determine if particular ingredi­ents are cytotoxic, whereas the ZK 1200[dermis and nondifferentiated epidermis]resembles the human cornea and is usedfor ocular testing."

Rosemarie Osborne. a senior scientist atProcter & Gamble's Human Safety De­partment, has experience with a number ofthtee-dimensional alternatives. According toOsborne, an advantage of these analogs isthe abiliry to apply test materials direcdyonto the tissue surface, without first dilutingthem in aqueous solution. "We were look­ing for a human cell-based system we coulduse for screening ocular irritants. We had aneed to apply materials that are traditionallydifficult to apply in vitro, such as granularlaundry derergents. We wanted to test thosein the same way in which people mightencounter them, such as when these deter­gents accidentally get into a person's eye."

During testing, once an agent or chem­ical is applied to the skin analog, theresponse can be monitored by such mark­ers as changes in cell morphology, expres­sion of protein markers and inflammatorymediators, and cell membrane integriry. Aspecific effect is indicated by the presenceof an endpoint marker. For example,inflammation is indicated by the presenceof cyrokine intedeukin I, a protein mole­cule that activates an inflammatoryresponse in body tissues. The rype of cellin the model being used, as well as themechanism of action of the agent undetinveStigation, help determine which of var­ious endpoint markers ate used. "The end­point market you choose is very muchdependent on what kind of agent youapply topically," says Ponec. She goes onto explain that it is best to choose a barreryof such matkers because each agent has aspecific mechanism of action that can bereflected by a variety of cell and tissuechanges.

The potential to use some markers forthe eady detection of changes that occurmore slowly during the inflammatory orrepair process is a unique fealUre of manyin vitro systems. Ponec, who is evaluatingmessenger RNA as an eady marker, says,

"If something is a strong irritating sub­stance, yOll get an early yes or no answerwhich is fairly obvious. In daily life, youhave a lor of mild irritants." Such irritantsinduce changes more slowly, with repeateduse over a long period of time. For this rea~

son, some investigators follow their cul­lUres for days or weeks to observe subdeeffecrs at rhe cellular or molecular levels,often before effecrs can be measured in invivo counterparts.

Skin2 is the only skin analog of irs kindbeing marketed in rhe Unired Sraresbecause there is litde demand for rheseproducts so far. Biotechnology companiessay this lack of demand is evidence of thefact that there is still not a major emphasison developing and applying in vitro meth­ods for toxicology testing. Still, Rheinsremains hopeful: "Advanced TissueSciences continues to make strong effortsand investments in laboratory toxicologykirs. The in virro market, albeit small atpresent, will continue to grow with addi­tional recognition and approval from theglobal regulators. We are also looking atways to bring costs down while increasingavailabiliry across all sectors of the indus­rry, including government and research."

The Eyes Have ItAmong the scientific and moral concernsrhat drive the developmenr of in vitroanalogs, perhaps one of the strongest isopposition to the Draize eye test, whichevokes strong sentiments among opponentsto rraditional animal testing. Jacob Sivak, arthe Universiry of Waterloo in Ontario, hasdeveloped an in vitromethod for scanning rheoptical qualiry of cullUredlenses. Sivak harvests lensesfrom the eyes of slaughter­house catde, using tech­niques that he developedwhile investigating damageto the eye from low con­centrations of ulrtavioletradiation. "The idea was tobe able to take the lens outof the eye and keep it alivefor long periods of time,then use it to test for possi­ble causes of cataracrs," heexplains.

Lens cells ate highlysensitive and teadily reflectdamage from very lowdoses of ulrraviolet tadia­tion. Anaromically, theyconsist of only epithelialcells, the same rype of cellfound on the ouret sUlfaceof the cornea and on the

surface of the body. All arise from the sameembryological source and, as such, providethe scientific basis for using skin analogs toassess eye irritation.

Sivak uses the refractive abiliry of thelens as an endpoint when monitoring lensfunction in vitro. The lens is rreated with achemical and placed in a lens culturechamber which he describes as "similar toan arrificial eye." A laserbeam is verticallyaligned from below the chamber and passesthrough the lens, which refracts the light.This change in direction is filmed by atelevision camera and fed inco a computer,which ca!culares the angle of refraction.

One of Sivak's greatest problems hasbeen how to measure toxicity withoutdamaging the lens. "Basically, we've devel­oped a technique where we can dip thelens in a [toxic] solution for shorr periodsof time," Sivak says. This allows him totest a range of toxicities, ftom highly toxicto "silUations where the material is lesstoxic in very low concentrations," he says.

Sivak has tested a number of chemicals,including a!cohols, surfactants, ketones,and acetates. He has also worked withcompanies such as Apotex Inc. in Toronto,(0 measure roxicity of various chemicals."What we needed to do was assess the toxi­ciry ofsome of the components of a vehicle[a substance used to delivet a drug] wewere developing," explained WilliamJacobson, director of innovative drugdevelopment at Apotex. "The work wasuseful and helpful, and we used the resulrsin our continuing formulation develop­ment," he said.

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1015

S L t, (, 1'1 I Il RI \ Ill" (,

De Wever B. Rheins L. Skinz: an in vitro human skin analog. Altern Methods Toxicol10:121-131 (1994).

Osborne R. Perkins MA. An approach for development of alternative test merhodsbased on mechanism ofskin irrirarion. Food Chern ToxicoI32:133-142 (1994).

Ponee M. Reconstructed human epidermis in vitro: an alternative co animal testing.A1rern Lab Anim 23:97-110 (1995).

Rheins L, Ehalen E. Donnelly TA. Naughron G. The development of three-dimen­sional in VillO human tissue models. Hum and Exp ToxicoI13:853-859 (1994).

Sivak J. Herberr KL. Fonn D. [n vitro occular irritancy measure of four contacr lenssolutions: damage and recovety. CLAO J21:169-174 (1995).

Innovations' In Vitro Innovations

The ability to measure recovery fromdamage is a key issue in roxicity resring. "[fthe chemical does damage the eye. forexample," says Sivak. "bur rhe damage canbe repaired. it is less of a risk than if thedamage is permanent." Many early in vitroalternatives did not measure recovery.Sivak. who was recently awarded a grantfrom the Canadian government ro specifi­cally look at lens recovery. says that theintaer lens rerains its ability ro repair dam­age. but damage and recovery do notalways correlare. The degree of recoveryvaries: rhe lens with the greatest damagefrom a chemical may also show the grearesrdegree of recovery. To measure recovety inSkinz sysrems. the chemical is washed fromrhe epithelial surface. which is rhenobserved for several days ro see if it returnsto its normal physiological state. accordingto Rheins.

AWorld of PossibilitiesDespire the currently small American mar­ker for skin analogs and other in vitro rech­nologies. the pace of their development haspicked up in recent years. due in parr rothe projecrions of rhe European Com­mission. The EC has targeted [998 as theyear that they will expecr cosmerics com­panies to use in vitro alternatives wheneverthey are available and the methods are sci­entifically sound. "That has global ramifi­cations. All rhese companies work in aglobal marketplace; they're not going tomake different products ro meet differentin vitro testing needs,» says Rheins.

William Srokes. associare director foranimal and alternative resources in theEnvironmental Toxicology Program at the

N[EHS. says that scientific validity is a keyconsideration in the directive. Stokespoints out that the basic science involvedin many of these in vitro systems maypoint rhe way ro one of their most valuableroles, providing information about themechanism of action of a parricular toxicresponse. This in turn may allow regula­tors and investigators to better determineboth the qualitative and quantirative rele­vance of the in vivo method.

Encouraging news about rhis kind ofapplication grew out of a 1993 interna­tional workshop sponsored by the UnitedStares Interagency Regularory A1rernativesGroup ([RAG). As a result of that meer­ing, "rhe U.S. [RAG has recently submit­red a proposed resting scheme for acuteocular irrirance," explained Stokes. "Theproposal, which allows for the considera­tion of in vitro test data. was submitted rothe Organization for Economic Cooper­arion and Development."

[n this proposal. in vitro merhods donot replace in vivo models, but dataaccrued using alternatives are considered indetermining what type of animal testingshould be done. Stokes describes it as aweighr-of-evidence approach ro roxicity.testing thar considers all available informa­tion about a chemical including physicalcharacteristics and chemical structure­aerivity data. This approach allows for sci­entifical[y based flexibility in the in vivotesting rarher rhan rhe standardizedapproach ofren used.

As newer alternatives become available,they will continue to enhance toxicity test­ing while addressing the moral and ethicalconcerns of using live animal models. [ndefining the mechanism of acrion forchemicals, analogs continue to capiralizeon what some believe is their greatest asser.

Mary Weideman

American Association for the Advancement of Science Annual Meetingand Science Innovation Exposition

AMSIEFebruary 8-13,1996

Baltimore Convention CenterBaltimore, MD

For information: Stephenie Brooks 1333 H. Stree~ NW Washington. DC20005(202) 326-6711

1016 Volume 103, Number 11, November 1995. Environmental Health Perspectives

If you cough a lot, wheeze, are short of breath or feel tightness in yourchest, you just might have asthma. If you do, you need treatment to control it.

So find out for sure. Catch your breath and see a doctor.

....easier. Ask your doctor if it's asthma.National Asthma Education Program

National Heart. lung. and Blood Institute; National Institutes of Health; Public Health Service; U.S. Department of Health and Human Services.

.Research

The Risk of Childhood Cancer from Intrauterine and PreconceptionalExposure to Ionizing RadiationRichard Wakeford

British Nuclear Fuels pic, Risley, Warrington, Cheshire WA3 BAS UK

The findings of studies investigating whether exposures to ionizing radiation before binh, eitherpre- or post-conception, increase the risk of childhood cancer have provoked much scientific con­troversy. An epidemiological association between the abdominal exposure of pregnant women todiagnostic X-rays and childhood cancer was first reported in the 19505, while an associationbetween the recorded dose of radiation received occupationally by fathers before the conceptionof their offspring and childhood leukemia was reporred only recendy in 1990. The scienrificinterpretation of these particular statistical associations is by no means straightforward, but thelatest analyses of intrauterine irradiation and childhood cancer indicate that a causal inference islikely. Scientific committees have adopted risk coefficients for the intrauterine exposure ofsomatic tissues, which for childhood leukemia are comparable to those accepted for exposure ininfancy, although quesrions remain about the level of risk of childhood solid rumors imparted byexposure to radiation in utero and shortly after binh. In contrast, the association between pater­nal preconceptional radiation dose and childhood leukemia has not been confirmed by studiesusing objectively determined doses. The original association has been found to be restricted tochildren born in one village, it does not extend to cancers other than leukemia, and it is markedlyinconsisrenr with the established body of knowledge on radiarion-induced hereditary disease. Acausal interpretation of this association has effectively been abandoned by scientific authorities.Key words. causal inference, childhood cancer, childhood leukemia, intrauterine exposures, ioniz·ing radiation, preconceptional exposures, radiation epidemiology, radiation risks. Environ HealthPerspecr 103:1018-1025 (1995)

In a recent wide-ranging review of adversehealth effecrs afrer exposure ro low levels ofionizing radiation, Nussbaum andKohnlein (1) drew attention ro the resultsof various epidemiological srudies of child­hood cancer, parricularly leukemia, amongindividuals exposed to radiation beforebirth, both pre- and post-conception. Theseresults were used to suggest carcinogenicrisk coefficients (risks per unit radiationdose), which were appreciably larger thanthose adopted by national and internationalscientific bodies, implying that the risksassociated with such irradiation have beenunderestimated for rhe purposes of radio­logical protection. Much scientific evidenceon this subject has recently become avail­able, and the aim of this review is ro deter­mine whether the inferences of Nussbaumand Kohnlein (1) concerning these particu­lar exposures can be sustained in the light ofthis additional information.

Intrauterine IrradiationA positive statistical association betweendiagnostic abdominal X-ray exposure ofpregnant women and cancer in children wasfirsr reporred in the 1950s from the OxfordSurvey of Childhood Cancers (OSCe), acontinuing case-control study of cancerdeaths occurring among children under 16years of age in Britain (2-5). The interpre­tation of this association has been the sub-

ject of considerable scientific debate overthe years (6, 7). The most recent analysis ofOSCC data, covering nearly 15,000 deathsbetween 1953 and 1979, suggests an excessrelative risk associated with an intrauterineX-ray examination of about 40% (8).

Many other studies of in utero irradia­tion and childhood cancer have been con­ducred, including a large case-controlsrudy of approximately 1300 cancer deathsamong those under 20 years of age bornduring 1947-1960 in the northeasternUnited States (9,10). The case-controlsrudies have produced a reasonably consis­tent picrure of positive associations; Bithell(11) has calculated the weighted average ofthe relative risks obtained from all the pub­lished studies except the OSCC to be 1.37(95% CI, 1.26-1.49); if the OSCC isincluded, the weighted average is 1.39(95% CI, 1.33-1.45). The association hasnot been confirmed by cohort studies,including the follow-up of almost 40,000British children who were X-rayed in utero(12), although one of the authors of thisstudy has since expressed doubts over thecompleteness of follow-up (13). However,the sratistical power of these cohon studieshas generally been insufficient to excludeexcess relative risks of the magnitude sug­gested by the case--control srudies (11).

Uncenainties regarding the accuracy ofX-ray examination reports based on recall

of mothers have largely been resolvedthrough the use of contemporary medicalrecords (5,9,14). Possible confounding fac­tors related ro both rhe X-raying of preg­nant women and childhood cancer (primar­ily those concerned with maternal illness)have been addressed through srudies oftwins X-rayed (at a higher frequency thansingleton birrhs) predominantly for obstet­ric purposes and not for reasons involvingthe general health of the mother. Thecase-control studies that have been con­fined to twins have produced excess relativerisks of childhood cancer associated with anintraurerine X-ray examination comparablero those for singleron birrhs, despite the dif­fering frequencies of such examinations(15-17). It should be noted, however, thattwins in general experience a rate of child­hood cancer which is similar to, ifnot lowerthan, that for singleton births (15,18,15tJ,although it is unlikely thar an excess riskdue to fetal X-ray examinations of the mag­nitude expected could be detected in thetwin follow-up studies reponed so far (19).There is no indication that an increased fre­quency of postnatal X-rays might accountfor the findings for twins (11), or generally(20. Later studies have also considered rheeffeclS of other potential confounding fac­tors such as marernal age (5,10).

Bithell (11) has shown that, because ofilS size, by far the most informative srudy ofintrauterine irradiation and childhood canceris the OSCC, and much of the derail of theassociarion has been derived from this srudy.An appropriate (i.e., linear) exposure­response relationship was originally demon­strated in an analysis of the OSCC data byStewart and Kneale (4) in terms of thenumber of X-ray exposures, or films, used inan obsteuic examination. This exposure­response relationship was not confirmed by alater analysis of the OSCC data (21), butBithell (11) has questioned the appropriate­ness of this particular analysis, demonstratingthat a linear exposure-response relationshipmay still be derived from the OSCC data.[Mole (22) has noted that multiple examina­tions during a pregnancy do nor seem rohave been taken into accounr in any of these

I am maS[ grateful to Sir Richard Doll and ColinMuirhead for commenting on this article. I thankChris Beresford for typing me manuscript.Received 12 April 1995: accepted 19 July 1995.

1018 Volume 103, Number 11, November 1995. Environmental Health Perspectives

Review· Prenatal irradiation and childhood cancer

analyses.] Mole (22) investigated the fetaldoses received during various X-ray proce­dures and concluded that a fixed estimate ofthe radiation dose per X-ray exposure couldnot be assumed. Consequently, wherher ornot an appropriate dose-response relation­ship exists is equivocal, although a lineardependence between exposure and relativerisk would certainly support such a relation­ship. Further, the magnitude of the relativerisk has decreased with calendar year ofbirth, which is consistent with the teductionin the dose per X-ray examination with time(II,22,23), indicating an underlying risinggradient of tisk with dose.

Experimental studies using animals, pri­marily rodents, irradiated in utero have nmproduced consistent evidence fot a carcino­genic effect (24). Howevet, recent informa­tion on dogs irradiated at various stages ofdevelopment confItms an excess incidenceofcancers among young dogs irtadiated justbefore or just after birth (25).

Given that ionizing radiation is anestablished cause of cancer when irradia­tion occurs postnatally, it would be antici­pated from the evidence ourlined abovethat the epidemiological associationbetween intrauterine exposure to diagnosticX-rays and childhood cancer would beintetpreted causally. Even though the avet­age fetal dose pet X-ray examination is low[around 0.5-5 cGy (26)], under theassumption of a no-threshold dose­response telationship, the carcinogeniceffect of such doses should be capable ofdetection, given a study of sufficient size.However, objections to a causal intetpreta­tion have been raised, and these have beenhighlighted by MacMahon (27) (the prin­cipal investigator in the case--<:ontrol studyconducted in the northeastern UnitedStates) and by Miller (28).

MacMahon (27) points ro three reasonsthe association between irradiation andchildhood cancer should be interpretedwith caution. First, the absolute tisk coeffi­cient derived from the association betweenchildhood cancer and diagnostic intrauter­ine irradiation is about an order of magni­tude greater than the equivalent coefficientderived from assessments of exposure inearly childhood, a difference that is difficultto explain biologically. Second, thete wasno evidence for an excess risk of canceramong children irradiated in uTero in theatomic bombings of Hiroshima andNagasaki, even though these individualsreceived. on average, doses several timesgreater than those exposed in utero to diag­nostic irradiation. Thitd, there is a similarelevation of relative risk associated with inutero diagnostic X-ray exposure across allthe major groups of childhood cancet,

which is uncharacteristic of other exposures.Knox et al. (23), in an analysis of the

latest updare of the OSCC database,derived an excess absolute childhood (0-14yeats of age) cancet mottaliry risk coeffi­cient of 20.2% (95% CI, 5.5%-29.0%)per Gy [cited by Nussbaum and Kohnlein(I)], which is substantially in excess of theequivalent tisk coefficient accepted for theitradiation of young children, as indicatedby MacMahon (27). However, Birhell (II)questioned the validiry of this analysis, andMuirhead and Kneale (8) pointed out thatan inappropriate assumption was implicitin the analysis of Knox et al. (23) whichled, in particular. to the excess relative riskassociated with births in 1950 being alllib­uted to the lower avetage radiation dose petX-ray examination received by those bornin 1960. When this was corrected, anabsolute risk coefficient fot childhood can­cer incidence of 13.6% (95% Cl,10.0%-18.4%) per Gy was obtained (8).Futther, the source of the mean doses perunit X-ray film used to derive this riskcoefficient (4) is somewhat obscure (2:!),and if the mean fetal doses per obstetric X­ray fIlm presented in the 1972 Repott ofthe United Nations Scientific Committeeon the Effects of Atomic Radiation(UNSCEAR) (29) ate used instead, theabsolute risk coefficient reduces to 6.4%(95% CI, 4.1 %-10.0%) per Gy (8).Muithead and Kneale (8) emphasize thatthese confidence intervals do not make fullallowance for uncertainties in the dose esti­mates or in the form of the relative riskmodel. The excess telative tisk wouldappear to be greatest at the age of 2-6yeats, and then decrease markedly at olderages (8), which is compatible with the find­ings of Monson and MacMahon (Ul).

These risk coefficients are detived fromanalyses of the OSCC data, which make us~of all exposures in all trimesters of pregnan­cy. Gilman et aI. (21) have suggested thatthe cancer risk due to irradiation in the fItsttrimester is 2.7 times that due to irradiationin the second and third trimestets; but mostof the available data ate for exposures laterin ptegnancy: mote than 90% of the infor­mation comes from third-trimester obstetricradiography (21). Moreover, many of theexposures in the first trimester were carriedout for nonobstetric reasons and occurredin the earlier years covered by the study,and these exposures (e.g., fluoroscopy)could well be associated with higher dosesthan those received during obstetric exami­nations (22). As a consequence, it is unclearfrom epidemiological data whethet the riskcoefficient for irradiation early in pregnancydiffers from that for third trimester obstet­ric X-raying.

Bithell and Stillet (30), in their analysisof the OSCC data, prefetted to adopt theUNSCEAR fetal doses, since the dosimerryscheme (4) used by Knox et al. (23) couldnot be reconciled with the rate of the tem­poral decline of relative risk apparent in theOSCC data. When restricting the analysisto the leasr uncertain data for thirdtrimestet exposures, they derived anabsolute childhood cancer risk coefficientof 4.5% (95% Cl, 2.7%-6.9%) per Gy(30). Under the assumption rhat the sameexcess relative risk coefficient applies to allthe major rypes of childhood cancer (5), anabsolute childhood leukemia risk coeffI­cient of 1.6% (95% CI, 1.00/0-2.4%) perGy is obtained.

Mole (2:!) has atgued that the only teli­able estimates of fetal doses that can beapplied to the OSCC data are those madeduting the comprehensive investigations ofthe Adrian Commitree in 1958. Applyingthese fetal dose estimates for third-trimesterobstettic exposutes to bitths in rhe OSCCdatabase during 1958-1961 (the avetagefetal whole-body dose per obstetric exami­nation being 6.1 mGy), Mole obtained anexcess telative tisk coeffIcient of 0.038(95% CI, 0.007-0.079) per mGy for child­hood cancer, giving an absolute risk coeffi­cient of 6.0% (95% CI, 1.0%-12.6%) petGy. The absolute risk coefficient for child­hood leukemia is 2.1 % (95% CI,0.4%-4.4%) per Gy.

Recently, Bithell (31) used a model hepreviously derived (11) to describe the vari­ation of the relative tisk of intrauterineittadiation with year of bitth, in combina­tion with the average fetal dose obtained byMole (22) from the Adrian Committeedata. From the model, the excess relativerisk associated with X-ray examinations in1958 is 0.31 (95% cr, 0.17-0.46), and theaverage fetal dose during this year is 6.1mGy. This leads to absolute risk coeffI­cients of8.1% (95% CI, 4.50/0-12.1%) perGy fot childhood cancet, and 2.8% (95%CI, 1.6%-4.2%) per Gy for childhoodleukemia, although these ate likely to beslight overestimates because nonobstetricexaminations wete included in the tiskmodel. Bithell (31) emphasizes the difficul­ties in obtaining accurate risk coefficientsfrom obstettic X-tay data and suggests thateven the most recent estimates could stillbe wrong by a substantial factor.

Of those Japanese who wete in utero atthe time of the aromic bombings ofHiroshima and Nagasaki in August 1945,1263 survivors could be followed completelyfrom birth to their 15th birthday (32). Theaverage dose received from the explosions bythis cohort is 184 mGy, with 753 of theindividual doses being at least 10 mGy. As

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1019

Review' Wakeford

noted by MacMahon (27). this average doseis substantially in excess of that estimated tohave been teceived by fetuses from diagnos­tic itradiation. Among this cohon. 2 cases ofcancet (not leukemia) occurred in individu­als less than 15 years of age. who bothteceived doses in excess of 300 mGy. Thenumbet of childhood cancet cases expectedfrom Japanese national dara is at most 0.73(32). giving an excess absolute risk coeffi­cient of 0.5% (95% CI, -0.2%-2.4%) perGy. As no cases of childhood leukemia wetediagnosed among the Japanese exposed inuraD. assuming that (at most) half of theexpected numbet of childhood cancers isdue to leukemia (32). an uppet 95% confi­dence limit of around I.l% pet Gy may bederived ftom this group for the absolutechildhood leukemia tisk coefficient.

It is unlikely that the childhood cancettisk coefficients obtained directly from theJapanese survivors irradiated in utero willchange substantially. Doses currently in useare 0586 uterine doses rather than fetaldoses (32). and neutron doses for those inHiroshima may be revised upwards (33).but it is difficult to see how final fetal doseswill have a major impact on these coeffi­cients. It should be noted that no cases ofcancer were recorded among the intrauter­ine-exposed survivors during the periodAugust 1945-Seprember 1950. Data forthis early period are inevitably less cenain(32), and analysis of the osee data set hasshown that the excess relarive risk of child­hood cancer associated with diagnostic x­ray exposure is greater for the 0- to 4-yearage group than for the 5- to 14-year agegroup (8). Mole (22) has argued that cellsterilization induced by high doses receivedduring the atomic bombings needs to betaken into account. and that this wouldhave the effect of at least doubling the riskcoefficients derived direcrly from the expe­rience of the Japanese irradiated in utero.On the other hand, it is conventional to

reduce the risk coefficients derived fromhigh-dose/high-dose-rate studies whenextrapolating to low dosellow-dose-rateconditions (34). So. whether there is a gen­uine incompatibility berween the level oftadiation-induced childhood cancer riskamong the Japanese bomb survivors irradi­ated in utero and that arising from fetalexposure to obsterric X-rays is unclear,given the remaining uncenainties in bothdata sets. However, what is clear is that anydiscrepancy is unlikely to be as great as thatsuggested by the childhood cancer morrali­ty risk coefficient of 20% per Gy derivedby Knox et al. (23) and cited by Nussbaumand Kohnlein (1).

It should be noted that a case-<:ontrolstudy of leukemia in Utah and radioactive

fallout from nuclear weapons testing inNevada found an association betweenchildhood acute leukemia and irradiationin childhood (consistent with the experi­ence of the Japanese atomic bomb sur­vivors). An association was not observed forsubjects in uraD at the time of the peakexposure to fallout (3.5). although becauseof the small numbers involved, this findingis unlikely to be incompatible with the riskcoefficients derived from medical expo­sures. Similarly, a study of childhoodleukemia in the Nordic countries in rela­tion to fallout from atmospheric nuclearweapons testing (36) found some evidencefor an excess risk due to irradiation inchildhood. at a level anticipated from high­dose studies. but not for intrauterine irradi­ation. However. since the average fetal doseduring the period of highest fallout wasassessed to be 0.14 mSv (36). it is unlikelythat the excess risk due ro this exposurecould be discerned statistically.

On the basis of the latesr resulrs fromanalyses of the osee data. the UKNational Radiological Protection Board(NRPB). while recognizing the uncertain­ties in fetal doses. has assumed an absoluterisk coefficient for cancer in childhood(0-14 years of age) following intrauterineirradiation of 6% per Gy (half of theseexcess cases resulting in death). taken to

apply to all trimesrers of pregnancy. ofwhich leukemia makes up 2.5% per Gy(again. half the cases being fatal) (34). Thisis consistent with the risk coefficient pre­sented in the BEIR V report of 2.0% to2.5% per Gy for death from cancer in thefirst 10 years of life (26). It is of interest tocompare this leukemia risk coefficient of2.5% per Gy with that adopted by theNRPB for irradiation in early childhood(34). which is based on the BEIR V relativerisk model derived principally from theJapanese bomb survivor data (26). For a10-mGy dose received just afrer birth. theexcess absolute risk coefficient for leukemiaoccurring before the age of 15 years is1.8% per Gy which. given the inherentuncertainties, is in good agreement withthe childhood leukemia risk coefficientassociated with in utero irradiation.

Of greater difficulty is the third objec­tion to a causal interpretation of the child­hood cancer and in utuo irradiation associ­ation raised by MacMahon (27). that simi­lar relative risks are found for all the majorgroups of childhood cancer. This is not thecase for cancers (mainly arising beyond theage of 15 years) among the Japanese bombsurvivors irradiated in early childhood (26)and leads to a considerable discrepancyberween the risk coefficienrs for childhoodsolid tumors following either intrauterine

or infant exposure. the in utero exposurecoefficient being much higher.

In 1975, Bithell and Stewart (.5) pre­sented relative risks, derived from theosee data. for the major types of child­hood cancers which showed that the excessrisk associated with in utero irradiation wasgenerally uniform across the groupings.Information in this detail has not been pre­sented since then, although more recentrepons have indicated similarly raised rela­tive risks for childhood leukemia andgrouped solid tumors (7.23). In contrast,Monson and MacMahon (J(J), in the latestanalysis of data from the northeasternUnited States. found a significanrly raisedrelative risk of leukemia of 1.52 (95% CI.1.18-1.95) but not of solid tumors (rela­tive risk 1.27; 95% el. 0.95-1.70).However. this solid tumor relative risk isnot statistically incompatible with thatgiven by Bithell and Stewart (.5) of 1.47(95% CI. 1.31-1.66).

It is undoubtedly the case that the can­cers of childhood are. in general. quite dif­ferent from those of adults. and it may bethat models derived [e.g., by BEIR V (26)]primarily from the study of adults are notappropriate for childhood solid tumors,particularly concerning a IO-year mini­mum latency. In this respea. it is of inter­est that experimental studies have showndifferences in tumor types in animals irra­diated either in utero or postnatally (24).Funher. information on the risk of child­hood cancer from those irradiated early inpostnatal life is limited (34). so the riskcoefficient for childhood solid tumorsobtained from fetal irradiation studies isnot necessarily inconsistent with the find­ings of studies of postnatally exposed indi­viduals. and the in utero exposure risk coef­ficient for childhood solid tumors may bethe most appropriate to apply to exposuresin early childhood. Certainly it is knownthat the relative risk coefficient for adultsolid tumors is greater for younger ages atexposure (34). so this would not beimplausible. However. this is an outstand­ing issue which requires resolution. Evenso. were the risk coefficient for childhoodsolid tumors derived from studies ofintrauterine exposure to diagnostic X-raysto be adopted for irradiation in early child­hood. this would have only a minor impacton population risk coefficients, since theseare dominated by the risk coefficients foradult cancers.

Apart from this last point, the difficul­ties in reconciling the findings of thecase-control studies of childhood cancerand fetal exposure to diagnostic X-rayswith the body of knowledge concerningradiation carcinogenesis have largely disap-

1020 Volume 103, Number II, November 1995· Environmental Health Perspectives

Review' Prenatal irradiation and childhood cancer

peared, due mainly to the results of morerecent studies. The risk coefficients associ~

ated with intrauterine irradiation adoptedby authoriries such as NRPB and BEIR Vare quite compatible wirh (and, indeed, arebased on) rhe OSCC dara, contrary to thesuggeseion of Nussbaum and Kohnlein (f).

Preconceptional IrradiationNussbaum and Kohnlein (1) discussed thepossible risk of childhood cancer, particu­larly leukemia, arising from preconception­al irtadiarion, noting rhe important impli­carions of rhis putative risk for radiologicalprotection and for radiobiology.

In 1984, rhe Independent AdvisoryGroup confirmed a media reporr of anexcess of childhood leukemia in the coasealvillage of Seascale, adjacent to the Sellafieldnuclear complex in West Cumbria,England (37). The group could find nocausal link between radioacrive dischargesfrom Sellafield and rhe leukemia cases, burrecommended rhat further research be car­ried our, including a case-<ontrol study. In1990, Gardner et al. (38) reported rhe pre­liminary results from rhe West Cumbrialeukemia and lymphoma case-conerolstudy, which examined a wide range of fac­roes possibly linked to the Seascale excess.The mose seriking findings were associa­tions between relarively high doses of ioniz­ing radiarion measured by film badgesworn by men employed at Sellafield beforethe conceprion of their children, and theincidence of leukemia in these children.The aurhoes suggested that this associarionwas sufficient to account for the childhoodleukemia cases in Seascale (39).

Gardner et al. repoered associationsborh with a cumulative preconceprionaldose of ~100 mSv and with a dose of ~ 10mSv received in the 6 months precedingconception, although these doses wetehighly correlated (38,40). Doses werebased on annual summaries of individualrecorded external whole-body doses, andthe average doses for the highest dose cate­gories were around 200 mSv and 20 mSv,respectively. Relative risks of 6-8 werefound, although because these were basedupon (the same) four cases and a similarlysmall numbet of controls, lower 95% con­fidence limits were less than 2. An appro­priate dose-response relationship was sug­gested only by the 6-month dose associa­tion. Similar associations were also foundfor childhood leukemia and non­Hodgkin's lymphoma combined, bur theresults were dtiven by cases of leukemia.

These findings were unexpected, asthere was no previous reliable evidence forpaternal preconceptional ittadiation andincreasing the risk of childhood leukemia,

particularly to the extent suggested by theseresults (41-43). However, the proposedexplanation for the Seascale leukemia caseswas attractive because of the failure ofother factors to account for the excess,including exposure of somatic tissues tosources of environmental radiation (39).

. The findings of Gardner et al. initiatedconsiderable scientific activity. Anothetexcess of childhood leukemia had previous­ly been reported from near the Dounteaynuclear installation in northern Scotland,and a case--eonrrol study of these cases wasalready underway when Gardner et al. pub­lished their findings. The results werereported in 1991 (44), and no associationbetween paternal preconceptional radiationdose and childhood leukemia and non­Hodgkin's lymphoma was found, althoughthe study was small and the findings werenot incompatible with those of Gardner etal. (45). However, this study did demon­serate that the excess of childhood leukemianear Douneeay could not be explained byfacrors associated with paternal employ­ment in the nuclear industry before con­ception, including radiation exposure.

Another case-conerol study com­menced in the 1980s to investigate anexcess of leukemia in young children livingnear the AldermaslOn and Burghfieldnuclear weapons facilities in WestBerkshire, England. In 1993, the results ofthis study were published (46). An associa­tion with farhers being monirored forexternal radiadon exposure in the precon­ceptional period was found (based on threecases and two controls with exposedfathers), but since recorded doses were low«5 mSv), there was no association wirhradiation dose. Incerestingly, in an equiva­lene comparison, Gardner et al. found noassociation wirh being monitored forexrernal radiation exposure (RR = 1.09,95% CI, 0.45-2.66) (40). However,Roman er al. (46) speculated as to whetherrhis association wirh radiation film badgeissue might be indicative of internalradioactive contamination or of someother occupational exposure. Paternal pre­conceprional employment in the nuclearindustry could not accounc for the child­hood leukemia excess in the Aldermaseonand Burghfield area.

The results of a fuerher study inprogress at the time of the report ofGardner et al. were published in 1991 (47).This case-concrol study examined threeareas in noerhern England where raisedlevels of childhood leukemia had beenreported, including part ofWese Cumbria.Owing to a large degree of overlap withthe study of Gardner et al. [only one casewith a recorded paternal preconceprional

dose (a total dose of I mSv) was notincluded in the data of Gardner et al.] thisseudy offers little in the way of indepen­dent evidence (48).

A review of epidemiological studies ofpreconceptional irradiation reported before1989 identified only one study whichfound an association berween paternal pre­conceprional radiation exposure and child­hood cancer or leukemia (49). Shu et al.(50) conducted a case-control study ofchildhood leukemia in Shanghai during1974-1986 and found an associationbetween childhood leukemia and rhe num­ber of preconceptional X-ray exposuresreceived by the father, as repoered ar inter­view. No similar association was found forreported maternal X-ray exposures.However, exposure information for over80% of farhers was supplied by mothers atinterview. In a subsequent case-controlstudy carried out by Shu et al. (51) ofchildhood leukemia in Shanghai during1986-1991, in which both mothers andfathers were interviewed, the associationberween childhood leukemia and paternalpreconceptional X-ray exposure was notconfirmed, indicating that the originalassociation was probably due ro recall bias.Recencly, however, Shu et al. (52) havepublished the results of a case-controlstudy of infant (0-18 months of age)leukemia in North America during1983-1988. Associations berween infancleukemia and paternal preconceptionalexposures of the abdomen CO diagnostic X­rays were found, and weaker associationswere found with chest and limb exposures.No similar associations were reported formaternal preconceprional X-ray exposures.Exposure data were based entirely on infor­mation reported by parents at interview.Of parents who refused to participate inthe study, about twice as many were con­trol parents as case parents, and of the par­ticipants, about twice the number of con­trol fathers refused co be interviewed com­pared with case fathers, which could beindicarive of potencial bias.

Shiono et al. (53) reported an associa­tion between cancer in young children andmaternal preconceptional X-ray exposure ina case-<oncrol study nesred within a cohortof children born during 1959-1965 acrossthe United States, rhe reported exposuredata being collected prospectively.However, the point estimate of the relativerisk for leukemia and lymphoma cases alonewas less rhan thar for all cancer cases, anddid nor differ significantly from 1.0 (C.S.Chung, personal communication). Grahamer al. (20) found an association berweenchildhood leukemia and maternal precon­ceptional X-ray exposure in a case-<onrrol

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1021

Toblo 1. The relative risk of childhood leukemia associated with a I cSv eumulative dose of radiationreceived by a father before the conception of a child, derived from substantive studies using objeetivemeasures of radiation dose published since the report of Gardner et al. (381'

[950-1989 whose fathers had received aradiation dose while employed at Sellafieldbefore the child's conception. Over 90% ofthese children were born in West Cumbriaoutside Seascale, and the Seascale-bornchildren accounted fot only 7% of the col­lective dose of paternal preconceptionalirradiation. This small fraction of the puta­tive excess risk of childhood leukemia asso­ciared with the Seascale-born children isincompatible with an explanation of theSeascale excess in terms of paternal ptecon­ceptional irradiation, since many moreleukemia cases should have occurredamong the childten of the Sellafield work­force born in the rest of West Cumbria(68,69). Dtapet et al. (70) demonsttatedthat the childhood leukemia excess inSeascale does not extend genetally to theremainder of West Cumbria.

Further, Kinlen (71) found a statistical­ly significant excess of childhood leukemiaand non-Hodgkin's lymphoma among resi­dents of Seascale who were born outsidethe village. This excess cannot be account­ed for by recorded doses of paternal itradia­tion before conception. Therefore, theassociation with paternal preconceptionalirradiation is not sufficient to account forthe excess cases which have occurred in thevillage.

Both Little et al. (67) and Wakefotd etal. (72) have examined the speculative sug­gestion that the confinement of the associa­tion between childhood leukemia andpaternal preconceptional irradiation tochildren born in Seascale might be due tosynergy between such exposure and somefactor [possibly related to infection(73,74)] restricted to Seascale. Such anexplanation is not viable because the inter­action would have to be implausibly strongto account for the pronounced geographi­cal confinement of the effect (67), and theinitiating mutation rate requited to ptedis­pose offspring to childhood leukemiawould have to be so high as to be incredi­ble (72). Furrher, synergy occurs betweentwo factors which act independently toincrease the risk of a disease (75), whereasno reliable evidence exists for paternalexposute to radiation befote conception

Review· Wake ford

study of childhood leukemia in three areasof the Unired Srares during 1959-1962. [na comparison of medical records with X-tayexposures reported at interview, consider~

able discrepancy was found (54). Evenwhen using exposure data ftOm medicalrecords, appreciable uncertainty musttemain because these tecords could only beaccessed for physicians, denrists, and hospi­rals mentioned at interview (54). [n ananalysis of OSCC dara, Kneale and Srewan(55) found no suppon for preconceptional(either marernal or parernal) X-ray exposureincreasing rhe risk ofchildhood cancer oncebiased recall had been taken into account.

Yoshimoro et al. (56) confirmed theabsence of any excess risk of childhoodcancer and leukemia among over 30,000offspring ofJapanese survivors of the atom­ic bombings of HitOshima and Nagasakiwho received a dose in excess of 10 mSv.The average preconceprional dose receivedby exposed fathers was 4[8 mSv. The find­ings of Gardner er al. concerning cumula­tive paternal preconceptional irradiadonare incompatible with the absence of anexcess leukemia risk among rhe Japanesechildren, whether paternal or joinr parenraldoses are considered (57-59). [n addirion,the absence of any discernible excess risk ofleukemia among 263 children conceivedshortly after the bombings whose fathersreceived a dose ~10 mSv (average dose, 257mSv) is inconsistenr wirh the findings ofGardner er al. (60).

Subsequenr to the publication of theresults of Gardner et al., two large case--<:on­rrol srudies were initiated. Kinlen et al. (61)found no association between recordeddoses of paternal preconceprional irradiarionand childhood leukemia and non-Hodgkin'slymphoma in a case-ronrtol study coveringrhe whole of Scotland for [958-1990.Similarly, in a case--<:onrtOl srudy of child­hood leukemia cases born to mothers resid­ing near nuclear facilities in Ontario anddiagnosed during [950-1988, no evidenceof an increased risk due to recorded parernalpreconceprional irradiation was found (62).This study also found no association withthe dose received from monitored occupa­tional exposures to tritium. Little (63) hasdemonstrated that the combined tesults ofthe Scottish and Onrario srudies are incom­patible with the findings of Gardner et al. atmarginal levels of statistical significance(two-sided p" 0.1).

Recently, Michaelis et al. (64) havereponed rhe results of a historical cohortstudy of children born to fathers workingin the West German nuclear industry.They found no evidence for an increasedrisk of either childhood cancer or leukemiadue to paternal preconceptional irradiation.

The results of Gardner et al. prompteda comprehensive investigation of canceramong the children of the male Sellafieldworkforce by the UK Health and SafetyExecutive (65,66). [n a case-ronrrol srudy,conducted as parr of this investigation, itwas found that the association betweenchildhood leukemia and non-Hodgkin'slymphoma and the tecorded doses of radia­tion from external sources received byfathers over the entire preconceptionalperiod is confined to children born in thevillage of Seascale. The strength of thisassociation in Seascale is statistically incom­patible with the absence of an associationin children born outside this village. Nooccupational exposure examined couldexplain the confinement of the associationto Seascale children. The association doesnot extend to childhood cancers other thanleukemia and non-Hodgkin's lymphoma.(In fact, a negative association betweencumulative pteconceptional dose and othercancets was found.) The Health and SafetyExecutive study demonstrated that theoriginal association teponed by Gardner etal. concerning the 6-month preconception­al dose was an artifact of the pro rata dosesobtained from annual dose summaries.This association with the 6-month dosewas not replicated using original film badgerecords, nor was an association found withthe dose received in the more biologicallyappropriate 12-week period before concep­tion, whether or not the analysis was con­fined to Seascale-born subjects.

Using data from the report of theHealth and Safety Executive, Little et al.(67) demonsttated that the Seascale associa­tion is not only incompatible in regard tothe lack ofan association fot children of theSellafield workforce born in the rest of WestCumbria, but also in regard to the absenceof any association in the children of theScorrish and Ontario radiation workers andin the offspring of the Japanese atomicbomb survivors (Table I). The Seascaleassociation is inconsistent with the negativefindings of all other epidemiological studiesusing objective measures of radiation dose.

Parker et al. (68) identified more than9,000 children born in Cumbria during

Data set

Offspring of Sellafield workforce born in Seaseale 165,66)Offspring of Sellafield workforce born in the rest of West Cumbria 165,66)Offspring of Ontario radiation workers 162)Offspring of Seottish radiation workers 161)Offspring of Japanese atomie bomb survivors 151>1

'After Little et aI.167). using a linear relative risk model.

Relative risk per leSv 195% CII

4.50 12.33-8.2011.0310.95-1.241

0.961<0.93-1.241<0.951<0.95-1.201<1.001<1.0ll-1.01l

1022 Volume 103, Number 11, November 1995· Environmental Health Perspectives

Review' Prenatal irradiation and childhood cancer

having a leukemogenic effect in the absenceof the "Seascale factor."

One suggestion made by Gardner et al.(38) is rhat doses of external radiarionexposure might be acting as a surrogate fordoses due to internally deposited radionu­elides, an interpretation favored by Romanet al. (46). As noted by Nussbaum andKohnlein (1), some support for this propo­sition was provided by Sorahan andRoberts (76) using data from the osee.They found an association betweenassessed potential for exposure to radionu­clides and childhood cancers other thanleukemia and non-Hodgkin's lymphoma,but not for leukemia and non-Hodgkin'slymphoma. However, the assessed poten­tial for exposure to radionuclides wasbased solely on job descriptions providedat interview, and Sorahan et al. (77) havesubsequenrly concluded that this associa­tion was due to information bias.(Interestingly, this lauer study found noexcess risk of childhood cancer or leukemiaamong offspring of radiologistS or indus­trial radiographers.) Moreover, the Healthand Safety Executive (65,66) found noassociation between childhood leukemiaand non-Hodgkin's lymphoma or otherchildhood cancers and internal radiationdoses to the testes, based upon biologicalmonitoring data ar Sellafield. This is con­sistent with the recent study of Anderssonet al. (78), who found no excess risk ofleukemia and non-Hodgkin's lymphomaor other cancers among the offspring ofDanish patients given injections of theradioactive contrast medium Thorotrasr,who were associated with an estimatedaverage internal preconceptional dose tothe testes ofaround I Sv.

The hypothesis generated by the studyof Gardner et al. (38)-rhat exposure offathers ro radiation before the conception oftheir children leads to an increased risk ofleukemia in these children-has nor beensupported by subsequent epidemiologicalstudies and is inconsistent with the currentunderstanding of radiation-induced adve"eheritable effecrs (34,79). The heritablecomponent of childhood leukemia is small[around 5% (80)], and the currenrly accept­ed risk coefficient for all hereditary effectSimplies that less than two excess cases of asevere hereditary disorder would beobserved in children of the male Sellafieldworkforce compared with a "background"of around 340 cases among this number ofchildren (69). A study of obsteuic out­comes of pregnancies in women residing inSeascale found no evidence of an excess riskof adverse effectS that might be related toheritable genetic damage (81), although thisstudy was based on just 228 pregnancies.

The findings of Gardner et al. led to alengthy court case heard in the High eourtin London during 1992-1993. Manyexpert wimesses from around the worldgave evidence in a 90-day hearing. Thejudge concluded that on the basis of thescientific evidence "the scales tilt decisive­ly" against paternal preconceptional irradi­ation being the cause or a material contrib­utory cause of the Seascale childhoodleukemia excess (82). This conclusion isconcordant with that of scientific authori­ties: a causal interpretarion of the associa­tion between childhood leukemia andpaternal preconceprional irradiation report­ed by Gardner et al. cannot be sustained(13,83).

ConclusionsThe epidemiological evidence reviewedhere does nor indicate rhat rhe risk ofchildhood cancer arising from intraurerineirradiation or irradiation of parents beforeconceprion has been underestimated bynarional and internarional bodies responsi­ble for assessing radiation risks. The riskcoefficients associated with incraurerineirradiarion which have been adopred bythese commirrees are consistent with theresults of the latest analyses of the oseedata, contrary to the suggestion ofNussbaum and Kohnlein (1). No reliablesuppOrt exists for the association betweenchildhood leukemia and paternal precon­ceptional radiarion dose, which has beenfound ro be confined to the children bornin rhe village of Seascale and which doesnot extend to other childhood cancers; rheoriginal association reported by Gardner etal. (38,39) seems most likely to have been achance finding.

Doll (84) has reviewed rhe evidencefrom orher epidemiological studies ofgroups exposed to low levels of ionizingradiation, particularly nuclear indusuyworkers and popularions exposed tonuclear weapons testing fallout. He con­cluded that rhe evidence from these studiesis compatible with the risk coefficientsderived by narional and internarional scien­rific comminees from the studies of thosereceiving higher doses, especially theJapanese atomic bomb survivors. This con­elusion is consistent with the scientific evi­dence reviewed in this paper.

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65. Health and Safety Executive. HSE investigationof leukaemia and other can~rs in the childrenofmale workers at Scllafield. Sudbu')'. UK,HSEBooks. 1993-

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69. Wakeford R. Tawn Ej, McElvenny OM, SCOttE, Binks K, Parker L, Dickinson H, Smith J.The descriptive statistics and health implicationsof occupational radiation doses received by menat the Sellafield nuclear installation before theconception of their children. J Radiol Prot14,3--16 (1994).

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77. Sorahan T, Lancashire RJ. Tempereon DH,Hcighway P. Childhood cancer and paternalexposure to ionizing radiation: a second reponfrom the Oxford survey of childhood caDC%rs.AmJ Ind Mod 28:71-78 (1995).

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ISSX 1996 European Spring WorkshopFood Toxins and Host Mechanisms

Conditioning Toxic Responses

Sitges, SpainJune 1-4, 1996

This European ISSX Workshop will take place Saturday, June I-Tuesday, June 4 in the lovely seashore city ofSitges, located 30 km south of Barcelona. Workshop attendance will be limited.

The objective of the workshop is to bring together both senior and young scientists to present and discuss theirlatest contributions in diverse areas of host mechanisms, such as mechanisms of tOXicity, role of biotransforma­tion enzymes, and inhibitory and inducing effects which condition the response of xenobiotics. There will be par­ticular emphasis on compounds present in diet. In addition to the opportunity for poster and oral presentations,the following subjects will be covered in scientific sessions:

• mechanisms of toxicity• role of biotransformation enzymes• inhibitory and inducing effects• natural and artificial food toxins

Local OrganiZing CommitteeAngel Messenguer, C/O, CSIC, Barcelona (Chairman)Josefina Casas, C/O, CSIC, BarcelonaMaria-Jose Gomez-Lechon, Hospital "La Fe", ValencioMargarita G. Ladona, IMIM BarcelonaAntonio Martinez-robed, Lab. Almirrall Barcelona

For further information please contact:

Prof Angel MesseguerDepartment ofBiological Organic ChemistIy, GO (CSIC)

J. Girono, 19. 08034 Barcelona, SpainTelephone: (34) -3-400612 f

FAX: (34)-3-2045904E-maU: issx96@cid.csic.es

Environmental Heahh Perspectives. Volume 103, Number 11, November 1995 1025

Articles

Sidestream Tobacco Smoke Exposure Acutely Alters Human NasalMucociliary ClearanceRebecca Bascom,1 Jana Kesavanathan,1.2 Thomas K. Fitzgerald, 1Kuo-Hsi Cheng,2 and David L. Swiftl

'Environmental and Airway Disease Research Facility, Division of Pulmonary and Critical Care Medicine, Department of Medicine,University of Maryland School of Medicine, Baltimore, MD 21201 USA; 2Division of Environmental Health Engineering, Department ofEnvironmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205 USA

Nasal mucociliary clearance (NMC) is a biomarker of nasal mucosal function. Tobacco smokershave been shown to have abnormal NMC, but the acute effect of environmental tobacco smoke(ETS) on nonsmokers is unknown. This study evaluated acute tobacco smoke-induced alterationsin NMC in 12 healthy adults. Subjects were srudied on 2 days, separated by at least 1 week.Subjects underwent a 6O-min conuoUed exposure at rest to air or sidestream tobacco smoke (55)

(15 ppm CO) in a conuoUed environmental chamber. One hour after the exposure, 99RYfc-sulfurcolloid was aerosolized throughout the nasal passage and counts were measured with a sClocilla­rion detector. Six out of 12 subjects showed more rapid clearance after smoke exposure than afterair exposure, and 3/12 had rapid clearance on both days. However, substantial decreases in clear­ance occurred in 3/12 subjects, all of whom had a history of ETS rhinitis. In two subjects, morethan 90% of the tracer remained 1 hr after tracer administration (2 hr after smoke exposure).Understanding the basis for biologic variability in the acute effect of tobacco smoke on NMCmay advance our understanding of pathogenesis of chronic effects of ETS. Key words. environ­mental tobacco smoke, inhalation toxicology, mucociliary clearance, nose, tobacco. EnvironHealth Pmpe't 103:1026-1030 (1995)

Environmental robacco smoke (ET5) is oneof the most common indoor pollutanrs andis associared with a tange of adverse healtheffecrs in both children and adulrs (J-6).We have focused on acute irriranr andrhinitis symproms ofvariable magnirudes inhealthy nonsmoking adulrs (J,7) and areinterested in understandiog the mechanismsof increased upper respirarory infectionsand increased asthma symptoms amongchildren (8J.

Our previous studies characterized theacute physiologic and inflammarory responseto sidesrream smoke (.7,~. ETS is defined asthe tobaceo smoke that nonsmokers inhale;it is composed of sidesrream robaceo smoke(5S) and exhaled mainstream smoke (MS).SS is the dominant component of ETS andcan be generated with a smoking machine.We have examined the response ro ETS byperforming controlled human exposure srud­ies with SS. SubjectS with a hisrory of ETSrhinitis symptoms demonstrate an increasedsymptomatic and objective congestiveresponse ro brief. high levels of S5 (45 ppmfor 15 min). Both subjects with and withouta history of ETS rhinitis demonstrate a con­gestive response to prolonged moderate levelsof S5 (15 ppm for 2 hr). The congestiveresponse lasrs less than an hour and occurswithout an increase in the permeabiliry ofthe nasal vasculature. as indicated by nochange in the concenrration of albumin inthe nasal lavage (7). Although the congestiveresponse subsides within 1 hr after exposure.patienrs repon symptoms lasting hours todays after exposure.

Clinically, a reduction in baselinemucociliary clearance indicates respiratoryrract injury. Clearance of panicles from therespiratory tract is an accepted biomarkerof respiratory rract function response rotoxicants (10), and clearance has beenquantified using saccharine. charcoal. andradio-opaque or radiolabeled rracers (J1).Proctor (11) concluded that a nasalmucociliary clearance (NMC) <1-2mmlmin was abnormal in healthy adulrs.Alterations in panicle clearance have beenused to characterize agent toxicity in ani­mal studies (12). Twenty years ago,Anderson et aI. (J3) noted anecdotally thatconrrolled SOz exposure caused the great­est inhibition of NMC in the human sub­jects who showed the greatest SOz-inducednasal symptoms. These findings suggestedthe broad hypothesis that subjecrs repon­ing increased symproms with exposure toan irritant might have inhibition of NMC.The purpose of the present study was rodetermine the effecrs of controlled side­stream robacco smoke exposure on NMCin healthy nonsmokers.

Materials and MethodsTwelve healthy, nonsmoking subjecrs wererecruited: six had a history of ETS sensitiv­iry and an objective. congestive response toconrrolled challenge with SS, and six hadno hisrory of ETS sensitiviry and no con­gestive response ro controlled challengewith SS. The selection ptocedure was asfollows: Healthy, nonsmoking, youngadults (ages 18-45) were recruited by

advenising at the Universiry of Maryland atBaltimore. "Nonsmoking" was defined as alifetime cumulative smoking history of lessthan 1 pack-year and no smoking in the last5 years. Subjects completed a health hisroryquestionnaire, and those with chronic car­diorespiratory conditions were excludedfrom the srudy. A screening questionnaireasked subjects to rate their hisrory andseveriry of symproms associated with expo­sure to environmental tobacco smoke on a0-5 scale (0 =no history of symproms. 1 =mild symproms. 3 = moderate symptoms, 5= severe symptoms). Symptoms of eye,nose, and throat irritation and headachethat occurred with hisrorical ETS exposurewere summed to calculate a "historicalETS-irritation index" and symptoms ofnasal congestion. rhinorrhea, sneezing. andpostnasal drip that occurred with historicalETS exposure were summed to calculate a"historical ETS-rhinitis index." Subjectswith an ETS-rhinitis index of 51 weretermed "ETS nonsensitive (ETS-NS)"; sub­jects with an index of >2 were termed "ETSsensitive (ETS-S)." This subject stratifica­tion has been used in prior srudies at ourresearch faciliry (7).

Prospective subjects underwent ascreening challenge with SS (15 ppm CO, 1hr) at rest. Those with a greater than 35%increase in nasal resistance were classified asdemonstrating a congestive response ro SS,those with a smaller than 5% increase innasal resistance were considered nonrespon­sive, and those with an increase in nasalresistance between 5 and 35% were consid­ered indeterminate. The 12 subjects werealso characterized with a history. nasalinspection, baseline nasal and lung func­tion, methacholine reactivity, and skin·prick test (J). Stratification was performedbefore controlled SS challenge followed bymeasurement of NMC. Subjecrs from thetwo gtoUpS were interspersed and data col­lection analysis and reduction completedbefore comparison of gtoup differences.

Address correspondence to R. Bascom,Environmental and Airway Disease ResearchFacility, 10 S. Pine Street, Room 800, Baltimore,MD 21201 USA.This research was supported by the Center forIndoor Air Research, Linthicum. Maryland.Received 17 April 1995; accepted 17 July 1995.

1026 Volume 103, Number 11, November 1995. Environmental Health Perspectives

Articles' Tobacco smoke exposure and mucociliary clearance

figure 1. Protocol. Each subject was studied on 2 days, separated by at least 1week. and exposed toclean air or sidestream tobacco smoke at a concentration of 15 ppm carbon monoxide. Nasal physiologymeasurements included symptoms measurements, posterior rhinomanometry and acoustic rhinometryand confirmed resolution of nasal congestion before aerosol delivery. The 99mTc-sulfur colloid aerosolwas delivered 1hr after completion of the smoke exposure.

l:l l!i l!i

5 r~ ~

'" '"

with 100 ppm isobutylene. Clean-air expo­sures were conducted in an identical man­ner except that cigarettes were not burned.

We began to assess NMC 50 min aftercompletion of smoke or air exposure, thattime at which the acute nasal congestiveresponse to smoke had resolved. An aerosol(colloidal 99mTc-sulfur in normal saline;Syncor, Timonium, Maryland) was deliv­ered to the nasal mucosa, with the cathetertip positioned 0.3 cm anterior to the inferi­or turbinate. A scintillation detector,placed anterior to the subject, made serialcounts for 60 min at 2-min intervals for 30sec each. Juxtaposing marks on the faceand detector ensured consistent alignment.Values were normalized to the initial countand expressed as percent reacer remainingat each time point. Between 40 and 50min after exposure. the activity remainingin each region of the nasal passage wasmeasured using a collimated derector.

The conditions of aerosol administra­tion were developed to effect diffuse depo­sition in the upper respiratory tract. Fiveadditional subjects were recruited to exam­ine the initial pattern of tracer deposition.The four additional detectors needed tomake this assessment were not available atthe time of the initial protocol, but thesefive subjects met the entty criteria for theinitial part of rhe study. Subjects under­went measurements immediately afteradministration of the aerosol to the leftnasal passage. The measurements weremade with the detector in four positions:centered at 2.5 cm, 3.5 cm, 7.5 cm, and10.5 cm posterior to the tip of the nose.Deposition was expressed as a percentage ofthe counts measured from the anteriorposirion. In rhe five pilor subjects, the

• Symptoms and t---1 Smoke/air exposurenasal phvsiology t--t Particle deposition

t---t Mucocilial)'clearance

•

activity measured by the anterior detecrorswas 26 ± 9% and deposition in the posteri­or two detectors was 18 ± II % of the ante­rior detector counts.

Statistical analyses (ANOVA) were per­formed with Excel (Microsoft Corp.,Redmond, Washingron). Because the ETS­Sand ETS-NS groups were selecred andstratified in advance of the srudy, the effectof smoke on NMC was analyzed separatelyfor each group.

ResultsTable 1 shows the characteristics and nasaldimensions of subjects at the rime of traceradministration (I hour after air or smokeexposure).

Figure 2 shows the average NMCcurves for the ETS-NS and ETS-S subjects.All subjects showed smooth decay curves,indicating consistent positioning andreproducible measurements. After clean-airexposure, the percent uacer remaining wassimilar in the two groups (ETS-NS 51 ±

14% versus ETS-S 41 ± 10%, nonsignifi­cant). After smoke exposure, the ETS-NSsubjects showed accelerared NMC, withonly 15 ± 3% tracer remaining (ETS-NS,air versus smoke, ,0<0.05). In contrast, theETS-S subjecrs had no change in meanclearance, with 46 ± 13% of the tracerremaining (ETS-S air versus smoke, p =

0.86).Figure 3 shows the individual subject

data 40 min after tracer administration. Sixof 12 subjects showed accelerated clearance(>35% less tracer remaining after smokeexposure than after air exposure). Three of12 fast-clearing subjects showed no changeafter smoke exposure compared with NMCon air-exposure days «30% remaining on

•

i;l ~ is g~ ~~ ~~

t~~

••

The order of the study days was varied andsrudy days were separated by at least Iweek. Figure I shows the study protocol.

An environmentally controlled researchexposure chamber was used ro limit expo­sure to the desired pollutant and to provideconstant conditions of temperature (22.2 ±

OSC) and relative humidity (40 ± 2%).The environmental chamber air supplyconsisted of ambient air passed throughhigh-efficiency particulate absolute(HEPA) filters to remove particles and acti­vated carbon filters to remove gaseous pol­lutants. The environmental chamber con­sisted of a 41-m3 clean room and a 22.2­m3 eXfosure room. A ventilation rate of3.0 m Imin in the exposure room enableda complete air change evety 7.5 min. All airin the exposute room was exhausted to theoutside without recirculation.

Reference cigarettes 2Rl F (Tobaccoand Health Institute, Lexington,Kentucky) were used for smoke generation,and SS was generated in a smoking cham­ber adjacent to the exposure room. Thegeneration system consisted of a 4.4-ft3

Plexiglass box containing three manifoldsconnected to a timing device. Intermittentpuffs were generated by sequentially open­ing solenoid valves connected to each man­ifold to achieve a negative pressure puff onthe filter end of the cigarettes. Humansmoking patterns were simulated by using a2-sec puff duration at a vacuum pressure of13.7 cm H20 to produce a 35-cc volumeof draw on each cigarette at I-min inter­vals. Mainstream smoke was' exhausted tooutside the building. Sidestream smoke wasintroduced into rhe exposure chamberthrough a ceiling diffuser and allowed toexit the chamber without recirculation.Burning cigarettes were replaced approxi­mately every 10 min during the study.Levels of SS were characterized by carbonmonoxide (CO) concentration in the expo­sure room, which was monitored cominu·ousty with an Ecolyzer Series 2100 COMeter (Energetics Science, New York) andwith a Bendix Model 8501-5CA InfraredGas Analyzer (Bendix Instruments,Lewisburg, West Virginia). A target con­centration of 15 ppm CO was achieved bycontrolling the number of cigarettespuffed. Subjects entered the exposure roomafter the target smoke concentration wasreached. Particle concentrations and distri­bution from 0.3 to greater than 10 ~m

(Climet Model 226-210 Multi-channelParticle Analyzer; Climet Instruments Inc.,Redlands, California) and total organicvapors (HNU-PIlOI, HNU, Inc.,Charlemont, Massachusetts) were alsomeasured during selected exposures. Theorganic vapor meter was calibrated daily

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1027

TImo(min)

DiscussionETS is one of rhe maS! common indool ailpolluranlS, and undersranding susceplibili­ry 10 irs adverse effeclS is of sciemific imel­esl and public healrh importance. The ple­scm dala indicare Ihal exposure 10 SS allevels similal 10 smoky, poorly vemilaledlOoms causes valiable effeclS on NMC ofhealrhy human subjccrs (14). The majoliryof Ihe subjcclS demonS!raled accelelalionof NMC wirh SS exposule 01 maimainedrapid clearance. Howevel, in 3 of rhe 12subjects, acute, coorrolled sidesrreamIObaceo smoke exposure resu!led in a sub­sranlial leduerion in NMC.

The nasal mucociliary clearance SYSlemused in this srudy was designed 10 aerosolizeIhe !lacer Ihloughoul Ihe nasal passage.This allows a search fOI eilhel diffuse 01

focal effects wirhin rhe nasal caviry. AnimalIOxicology Sludies show Ihal mucosallesions of rhe nasal passage diffel in rhe sileand rype of lesion depending on rhe loxin(11). Orhel merhods 10 assess mucociliarynIDerion, such as the saccharine, charcoal,and radi<Hlpaque disc merhods, only assessclearance in a single SIlearn from rhe inferi­or rurbinale 10 rhe Pharrnx (4).

A plevious srudy examined rhe effCC! ofexhaled mainslleam smoke on nasalmucociliary clearance of nonsmokers (15).Ten heallhy, nonsmoking volunleerssmoked rwo cigalelles each, exhaling Ihesmoke rhlough rheil nOSllils. Thele was noaCUle change in Iheil nasal mucociliaryfunerion as delected by Ihe mean ciliarybeal flequency 01 mean nasal mucociliaryclearance. Nasal mucociliary clearance wasalso S!udied in Ihree donkeys exposed 10

lobacco smoke (8); no aCUle change inclearance occurred.

Mucociliary clearance is an agglegalemeasure of mucosal funcrion and imegriry(](/). DetelminanlS of nOlmal funerioninclude Ihe quanriry and composilion ofairway surface fluid and rhe rype and func­rion of epilhelial cells, especially cilialed

both days).Three of 12 subjects (all ETS·S)showed subslamially increased !Clemion(>25% mOle lracel lemaining aftel smokeexposure than after air exposure). The thleesubjeers showing leduced clealance wirhsmoke compared 10 air exposure wele sub­jeer nos. 3, 4, and 5. There was no signifi­canl cOllelalion belween Ihe aerivilyremaining al 40 min and the nasal dimen­sions at the time ofaerosol administration.

Figure 4 shows the legional diSllibUlionof lracer 40 min aftel exposule in ETS-NSand ETS-S subjeclS. On avelage, ETS-Ssubjects showed increased relenrion of lrac­el al all siles in Ihe nasal passage afrersmoke exposure.

100 100

80 80

~..= 60 60'S

';~

·f .. ..~

20 20

0 00 20 .. 60 80 0 20 .. 60 80

Articles· Bascom et al.

T.~lol. Nasal dimensions when radioactive aerosol was delivered to the nasal passage and activityremaining at 40 min after exposure'

Subject %Activity Volumelcm3)

no. Characteristics' Exposure remaining Areamin,

Anterior Mid

ETS sensitivelSS responsived

1 F,26.NA Air 65 1.1 3.5 32.3Smoke 26 0.7 2.0 12.5

M,23,NA Air 84 0.7 2.5 27.2Smoke 49 0.7 2.2 22.0

F,2M Air 67 0.4 1.0 15.8Smoke 96 0.3 0.7 20.8

F,21,NA Air 23 0.4 1.1 05.1Smoke 51 0.5 1.6 05.3

M,24,NA Air 40 0.4 1.4 14.8Smoke 91 0.5 1.6 16.7

M,24,NA Air 78 0.9 2.2 13.1Smoke 24 0.7 1.7 10.6

ETS nonsensitive/SS nonresponsive

M,24,A Air 25 0.5 1.3 15.2Smoke 21 0.5 1.6 17.3

F,27,A Air 68 1.1 3.7 29.5Smoke 12 1.2 3.5 35.0

F,28,A Air 87 0.4 1.0 08.7Smoke 14 0.5 1.8 14.8

10 F,25,A Air 85 0.9 2.4 27.1Smoke 26 0.8 2.1 14.6

11 F,24,NA Air 26 0.7 2.1 15.7Smoke 10 0.7 2.1 18.3

12 F,25,NA Air 7 0.7 2.5 35.8Smoke 8 0.4 1.1 10.7

'Values shown are the dimensions of the nasal passage in which the tracer aerosol was delivered.-Sex, age in years; A, atopic as determined by a positive wheal-and·flare response to one or more skin·prick tests; NA, nonatopic as determined by anegative response to skin·prick tests."Minimum nasal passage cross-sectional area.<tsensitive/responsive subjects reported ahistory of rhinitis symptoms with environmental tobacco smokeexposure lETS sensitive) and demonstrated increased nasal resistance with a screening challenge withsidestream tobacco smoke ISS responsive).

Fig... 2. Total mucociliary clearance. (AI Resuhs for the environmental tobacco smoke-sensitive (ETS-SIsubjects (n = 6) and (B) resulls for nonsensitive IETS-NS) subjects In = 6). Clearance after air exposureand after smoke exposure are shown. Values are means ± SEM of counts made at 2min intervals for 30sec per count Clearance was normalized to the initial count At 58 min an anterior nasal wipe was per·formed, demonstrating that on all days only asmall quantity of the tracer was located in the nasal antrum.ANOVA: ETS-NS nasal mucociliary clearance INMC) post-air vs. ETS-NS NMC post-smoke, ·p.:1l.005;ETS-S NMC post-air vs. ETS-S NMC post-smoke, p= 0.86; NMC post-clean air ETS-S vs. ETS-NS, non­significant

1028 Volume 103, Number 11, November 1995· Environmental Health Perspectives

Articles' Tobacco smoke exposure and mucociliary clearance

Figure 1 Activity remaining in the nasal passage 40 min after exposure. (AI Results for the environmentaltobacco smoke-sensitive IETS-SI subjects (n =61and 18) results for the nonsensitive IETS-NS) subjects In=6).

interest. Nasal dimensions at the time ofNMC measurement were similar on the 2study days. making diffetences in initialtracer deposition unlikely. Small changes inNMC related to cyclic changes in nasalpassage volume are also unlikely to accounrfor the effects seen. Upper respiratotyresponses to numerous toxicants are quali­tatively similar berween humans and manyexpetimental animals (10.20.2J), and themechanisms of mucociliary clearance arethought to be similar in humans and mostother mammals. Animal slUdies haveshown that low-level irritant exposuteaccelerates mucociliary clearance.Acceleration of NMC has been demon­strated in humans with exercise (amibUledro adrenergic stimulation), nasal salineflush (arrributed to increased surface fluid).and phatmacologic agents such as g-ago­nislS and cholinergic agonisrs.

Animal studies have shown rhat higher­level irritant exposure inhibirs mucociliaryclearance (12.22). Our data suggest a possi­ble lefrward shifr in the exposure-responsecurve in some of our subjects. Possiblemechanisms for the teduction in NMCinclude include inhibition of ciliary beat­ing, altered viscoelastic properties or reduc­tions in airway surface fluid (13.22). Inhuman studies, few stimuli other thanex((eme dehydration markedly inhibitNMC(1J).

Other investigators have assessed theeffccrs of active smoking on baseline nasalmucociliary cleatance (1S). A comparisonof nonsmokers and smokets showed that28 current smokets had a mean clearancetime of 20.8 min. which was significantlylonget than the mean time of 11.8 min in27 lifelong nonsmokers. One smoker (notincluded in the average) had a cleatance>60 min. There was no significant diffet­ence berween the mean nasal ciliary beatfrequency of 10 smokers and 10 nonsmok­ers (measured on nasal scrapings). Theinvestigarocs interpreted this as evidencethat the periciliary environment (e.g., sur­face fluid and mucus rheology) wereresponsible for the impaired clearance andthat a ditect ciliary toxiciry was less likely.Studies of young smokers showed variousdegrees of impairment of tracheal mucousvelociry before the onset of bronchitissymptoms or evidence of airway obstruc­tion via pulmonary function teslS (10.23).

The clinical significance of these find­ings remains to be determined. We specu­late that the subjects with inhibition ofnasal mucociliary clearance after smokeexposure are at increased risk of chronicairway injury for (wo reasons. First,mucociliary clearance is an accepted bio­matker of pulmonary function (UJJ. and

D-1.S 1.5-3 3-4.5 4.5-6 6-1.5 7.5-9 9-10.5

varion of capsaicin-sensitive, c-fiber nerves(18.J9). In the dogs. capsaicin. adminis­tered as an aerosol fat 2 min. stimulates aninctease in ciliary beat frequency. Thiseffect is partially blocked by prior adminis­tration of indomethacin (a cyclooxygenasepathway inhibitot), ipratropium bromide(a muscarinic receptor antagonist). andhexamethonium btomide (a nicotinicteceprot antagonist). The time course ofthe increase in ciliary beat was observed coinclude an early phase, lasting 15 min. anda subsequent phase, lasting 30 minutes(11). These data suggest that activation ofthe chemosensitive nerves with sustainedincteases in ciliary beat ftequency couldaccount for the increased mucociliary clear­ance observed in six of the subjects in thisstudy. .

The inhibition of NMC in three sub­jeers after smoke exposure is of particular

0-1.5 1.5-3 3-4.5 4.5-6 6-7.5 1.5-9 9-10.5

'00 100

!J.. ....=:~~ 60 60E=!'e.~!i-5; 40 40..

20 20

Clean air Sidostrelm Clean air Sidestreamsmoke smoke

Horizontal Distanco lcml

Figure 4. Distribution of activity remaining in the nasal passage.IA) Results for the environmental tobaccosmoke-sensitive IETS-SI subjects (n =61 and (8) results for the environmental tobacco smoke nonsensi­tive (ETS-NS) subjects (n =6). Total ETS-NS nasal mucociliary clearance (NMCI post-air vs. ETS-NS NMCpost-smoke. p=0.06; ETS-S NMC post-air vs. ETS-S NMC post-smoke. nonsignificant

cells (12). Animal and in vitro studies indi­cate that airway cells may potentially bealtered by cigarelle smoke (12), althoughexposure levels used for animal studies wererypically higher than those used in thisstudy. In rodent models, tobacco smoke hasbeen shown (Q cause acute increases in vas­cular permeabiliry via activation of upperrespiratory capsaicin-sensitive neurons, aneffect that could inctease airway surfacefluid. However. previous human studies inout laboratory failed to show evidence forincreased nasal vascular permeabiliry withsmoke exposure at these levels (7,J6).

Studies of dogs have demonsttated aneffcct of stimulation of c-fiber neurons onciliary beat ftequency (11). These studiesare rdevam [Q the present study. as investi­garors have demonmated that the acuteresponse to robacco smoke in the uppetrespiratory tract of rodents occurs via acti~

Environmental Health Perspectives' Volume 103. Number 11. November 1995 1029

Articles· Bascom et al.

clearance is maintained in the face of manyinsults. Inhibition of cleatance suggests agreater degree of injury than unaltered oraccelerated clearance. Second, impairedmucociliary clearance has been associatedwith increased rates of infection and allet­gy, and these processes could produce fur­ther injury. Cystic fibrosis and ciliary dysk­inesias (e.g., Kartagener's syndrome) areconditions characterized by impairedmucociliary clearance and increased infec­tions. Animal studies have demonstratedthat exposure to ozone inhibits pulmonarycleatance of radiolabeled tracers and causesincreased primary allergen sensitization andsecondary anaphylaxis (24-26). Wood­workers with high dust-exposure levels hadincreased rates of impaired nasal clearanceand higher infection rates than those withlow dust-exposure levels (27).

Studies of the chronic alterations inmucociliary clearance in upper and lowerrespiramry tract disease have been inter­pteted as suggesting that loss of control ofmucociliary transport could either cause orresult from chronic respiratory disease (28).Adverse effects of active smoking includenonmalignant, chronic obstructive lungdisease and upper and lower respitaroryttact cancers (1,8,29). The basis for suscep­tibility to these effects is nor well undet­stood. even though numerous studies haveshown familial aggregation of chronicobstructive lung disease (30,3J).

OUt test, coupling SS exposute withNMC, meets initial criteria for a biomarkerof susceptibility for respiratory diseasebecause there is a relationship to respitatorydisease and because NMC is fairly sensiriveto change after exposure to appropriateagents (10). Additional characteristics thatwould need to be determined to estimatethe utility of NMC are its longitudinal sta­bility and population distribution.Interpretation of these acute smoke­induced changes in mucociliary clearancein terms of potential health problems isspeculative at present (JO).

Understanding the mechanism of thevariability in the NMC response to acutesmoke exposure will help assess its relation­ship to the symptoms of ETS-rhinitis,assess whether jt indicates subclinicalmucosal injury in healthy subjects, deter­mine whether there is an altered expo­sure-response curve, and determine if it isa marker of individual susceptibility to thechronic effects of mainstream or environ­mental tobacco smoke.

REFERENCES

1. u.s. Surgeon General. The health conse·quences of involumary smoking: a report of theSurgeon General. Washington, DC:Govern­ment Printing Office, 1986.

2. National Research Council. EnvironmentallObacco smoke: measuring exposures and assess­ing health effects. Washingwn, DC:NarionalAcademy Press, 1986.

3. NIOSH. Environmenla1 tobacco smoke in theworkplace: lung cancer and other health effects.In: NIOSH current intelligence bulletin 54.Cincinnati, OH:Narional In$[itUle forOccupational Safety and Health, 1991;1-18.

4. Glann SA, Parmley WW. Passive smoking andhean disease. Epidemiology, physiology, andbiochemistry. Circulation 83:1-12 (1991).

5. Glann SA, Parmley WW. Passive smoking andhean disease. Mechanisms and risk. JAmMedAssoc 273: 1047-1053 (1995).

6. U.S. Surgeon General. The health conse­quences of smoking: cardiovascular disease: areport of rhe Surgeon General. DHHS (PHS)84-50204. Washington, DC:U.S. PublicHealth Service, Office on Smoking and Heahh,1983.

7. Bascom R, Kulle T, Kagey-Sobotka A, ProudD. Upper respiratory tract environmentaltobacco smoke sensitivity. Am Rev Respir Dis143:1304-1311 (1991).

8. Weiss S, Tager I, Schenker M, Speizer F. Stareof rhe an: the health effects of involuntarysmoking. Am Rev Respir Dis 128:933-942(1983).

9. Willes S, Fingerald T, Bascom R. Nasal inhala­tion challenge s(Udies with sidesneam tobaccosmoke. Arch Environ Health 47:223-230(1992).

10. National Research Council. Biologic markers inpulmonary toxicology. Washington,DC:Narional Academy Press, 1989.

11. Proctor OF. The mucociliary system. In: Thenose. Uppet airway physiology and rhe atmos­pheric environment (Proctor DF. AndefS(:n lB.eds). New York:Elsevier Biomedical Press.1982;245-278.

12. Morgan KT. Patterson DL. Gross EA.Responses of the nasal mucociliary apparatus (Q

airborne irritants. In: Toxicology of the nasalpassages, (Barrow CS. ed). WashingtonDC:Hemisphere Publishing, 1986; 123-133.

13. Andersen I. Lundqvist GR, Jensen PL, ProctorF. Human response to controlled levels of sul­fur dioxide. Arch Environ Health 28:31-39(1974).

14. Sebben j, Pimm P, Shephard R). Cigarettesmoke in enclosed public facilities. ArchEnviron Health 34:53-58 (1977).

IS. Stanley P, Wilson R. Greenstone M,MacWilliam L, Cole P. Effect of cigarerresmoking on nasal mucociliary clearance and cil­iary beat frequency. Thorax 41:519-523(1986).

16. Willes S, Fingerald TK, Permurr T, Sauder L,Bascom R. Respir.atory effeCls of prolongedsidestream tobacco smoke exposure and effectof fihration. Am Rev Respir Dis 143:A90(1991).

17. Wong LB, Miller IF, Ye.ates DB. Stimulation oftr.acheal ciliary be.at frequency by caps.aicin. JAppl PhysioI68:2574-2580 (1990).

18. Lundberg )M, Saria A, Mankiog ER. Capsaicinpretreatment .abolishes cigarette smoke~induced

oedem.a in rat tracheo-bronchial mucosa.. Eur JPharmacoI86:317-318 (1983).

19. Lund~rg J. M.arding C, Saria A, Folkers K.Rosell S. Cigarette smoke-induced airw.ay oede­ma due to activiation of basaicin~sensitivevagaafferents and substance P release. Neuroscience10:1361-1368 (1983).

20. Phalen RF. Mannix RC. Drew RT. Inhalationexposure methodology. Environ He.althPerspecr 56:23-34 (1984).

21. Lippmann M, Schlesinger RB. Interspeciescomparisons of p.article deposition andmucociliary clearance in trachobronchi.al .air­w.ays. J Toxicol Environ Health 13:441-469(1984).

22. Clarke SW, Yeates D. Deposition and clear­ance. In: Textbook of respiratory medicine(Murray )F, Nadel )A, eds). Pbiladelphia,PA:W.B. Saunders, 1994;345-36.

23. Goodman RM, Yergin BM, Landa )F,Golinvaux MH, S.ackner MA. Relarionship ofsmoking history and pulmonary function testsro tracheal mucus velocity in nonsmokers.young smokers, ex~smokers .and patients withchronic bronchitis. Am Rev Respir Dis117:205-214 (1978).

24. Matsumura Y. The effects of ozone. nitrogendioxide. and sulfur dioxide on the experimen­tally induced allergic respiratory disorder inguinea pigs: III. The effect of the occurrence ofdyspneic auacks. Am Rev Respir Dis102:444-447 (1970).

25. Matsumura Y. The effects of ozone, nitrogendioxide. and sulfur dioxide on the experimen­tally induced .allergic respiratory disorder inguinea pigs: I. The effect on sensiriz..ation withalbumin through the .airway. Am Rev RespirDis 102:43(}..437 (1970).

26. Matsumura Y. The effects of ozone. nitrogendioxide, and sulfur dioxide on rhe experimen­tally induced allergic respiratory disorder inguine.a pigs: II. The effects of ozone on theabsorption and the retention of antigen in thelung. Am Rev Respir D~ 102:438--443 (1970).

27. Anderson I. Effects of .airborne substances onnasal function in human volunteers. In:Toxicology of the nasal passages, (B.arrow CS,ed). Washington, DC:Hemisphere Publishing,1986;143-154.

28. Alben RE, Lippmann M, Peterson HT Jr,Berger J. S.anborn K, Bohning DE. Bronchialdeposition and clearance of aerosols. ArchIntern Med 131:115-127 (1973).

29. U.S. Surgeon General. Smoking and health. Areport of the Surgeon General. WashingtOn,DC:U.S. Government Priming Office, 1979.

30. Buist AS. Obstructive diseases: smoking andother risk factors. In: Textbook of respiratorymedicine (Murray )F, Nadel )A, eds).Philadelphia, PA:W.B. Saunders, 1988;1001­1029.

31. Bascom R. Differemial susceptibility to tobaccosmoke: possible mechanisms. Pharmacogenetics1:102-IOG (1992).

1030 Volume 103, Number ", November 1995. Environmental Health Perspectives

XIV1h World Congress on Occupational Safetyand Health

April 22-26, 1996Madrid, Spain

The XIVth World Congress on Occupational Safety and Health will be held in Madrid from April

22 to April 26, 1996. The organizers are the Spanish Ministry of Labour and Social Security,

through the National Institute for Occupational Safety and Health (INSHT), the International

Labour Office (ILO), Geneva, and the International Social Security Association (ISSA), Geneva.

These World Congresses, of which the first was held in Rome in 1955 and the last in New Delhi in

1993, have had such venues as Brussels, Paris, London, Zagreb, Vienna, Dublin, Bucharest,

Amsterdam, Ottawa, Stockholm and Hamburg.

The XIVth World Congress, to be held in Madrid, aims to be an open forum for all persons involved

in risk prevention at work, safety and health safety specialists, occupational health physicians,

labour inspectors, persons directly concerned with safety and health at work, including entrepre­

neurs and managers in enterprises, trade union representatives, manufacturers and importers, as

well as heads of public administration and social security administrators.

The main focus of this Congress will be on the consequences for occupational safety and health of

processes of international and regional integration (e.g. ED, NAFTA) and of the globalization of

economic relations, on an in-depth analysis of chemical risks and on new proposals for cooperation

and participation within enterprises. Other specific issues will also be dealt with, such as training

and information, control of working conditions or new responsibilities. Special emphasis will be

placed on small and medium-sized enterprises and sectors facing specific problems with regard to

safety and health at work, such as the construction sector and agriculture.

In addition, as part of this Congress, the International Section "Electricity" of the ISSA will be

organizing the 3rd International Film and Video Festival on Occupational Safety and Health.

Should you require any further information, please contact:

Secretaria del CongresoInstituto Nacional de Seguridad e Higiene en el Trabajo

CaUe de Torrelaguna, 73E-28027 Madrid-Spain

Tel. 34-1-404 57 36FAX 43-1-326 78 55

Biological Monitoring of Iodine, a Water Disinfectant for Long-term SpaceMissionsGrazyna Zareba,1.2 Elsa Cernichiari,1.3 Lowell A. Goldsmith, 1,2 and Thomas W. Clarkson1.3

teenter for Space Environmental Health, 2[)epartment of Dermatology, and 3{)epartment of Environmental Medicine, University ofRochester School of Medicine and Dentistry, Rochester, NY 14642 USA

In order to establish guidelines for exposure of astronauts to iodine, used as a water disinfectantin space, we studied the usefulness of hair, saliva, and urine for biological monitoring in humansand in the human hair/nude mouse model. The monitoring of iodine in patients that received150 mCi of Na l3l I (carrier-free) showed similar patterns of elintination for blood, saliva, andurine. The mean correlation coefficient (r) between iodine elimination for blood/saliva was 0.99,for blood/urine, 0.95, and for saliva/urine, 0.97. Tbe absolute value of iodine concentrations inurine revealed marked variability, which was corrected by adjusring for creatinine levels. Theautoradiographic studies of human hair demonstrated that iodine is rapidly incorporated intoenernallayers of the hair root and can be removed easily during washing. These data were con­firmed afrer iodine exposure using the human hair/nude mouse model. Hair does not providesatisfactory information about exposure due to unstable incorporation of iodine. The most use­

ful medium for biological monitoring of astronauts exposed to high doses of iodine in drinkingwater is urine, when adjusted for creatinine, and saliva, if quantitative evaluation of flow rate isprovided. Key words: astronauts, biological monitoring, blood, hair, human hair/nude mousemodel, iodine, saliva, urine, water disinfection. Environ Health Perspect 103:1032-1035 (1995)

The effective biological monitoring of astro­nauts during long-term flights represents anew aspect of environmental and humantoxicology. Iodine compounds, used by theNational Aeronautics and Space Adminis­tration (NASA) as warer disinfectants duringexrended space missions, can be a potentialhuman hazard (1,2). Exposure to excessiodine through foods, dietary supplements,topical medications, or iodinated contrastmedia widely used in clinical diagnostics canproduce toxic responses in humans includ­ing thyroiditis, goiter, hypothyroidism,hyperthyroidism, sensitivity reacrions, andacure responses (3-6).

An important aspea of biological moni­toring of asrronauts is to identify a mediumthat can recapitulate exposure to toxic sub­srances during the mission. Potential mediainclude blood, saliva, urine, and hair. Not allof these media, however, can be easily collect­ed and stored during long-lasting space mis­sions. According to numerous studies, humanhair can be a useful medium for biologicalmonitoring (7-1{}J. Hair has the potential toincorporate chemicals transported from thebloodstream into the follicle and subsequent­ly into the hair shaft. Thus, with a growthrate of approximately I cm/month, even ashort length of hair can recapitulate bloodlevels over periods ofseveral months (~.

In our previous studies (11), we demon­strated that human hait transplanted OntOnude mice can be used to evaluate humanexposure to different toxic substances. Thisunique system maintains human hair char­acteristics and incorporates toxic substances

in a fashion identical to that seen inhumans in vivo. The presence of excessiodine in hair has been reported in severalanimal and human srudies (12-11), butthis medium has not been critically evalu­ated as an indicator of iodine exposure.NASA has been using saliva for clinicalmonitoring of drugs (18), and this medi­um also should be considered because it isnoninvasive and high iodine concentra­tions are found in saliva (J9,2{}J.

Urine is widely used to estimate iodinestatus in subjects with dietary iodine defi­ciency, and the guidelines for minimumiodine concentrations in urine have beenalready established (21,22). Nevertheless,data on iodine levels in urine are scarce.Under space laboratoty conditions, iodineanalysis in plasma, due to very low concen­trations, as well as the other laboratorytests (i.e., triiodothyronine, thyroxine, orthyroid-stimulating hormone levels) will bedifficult to perform.

Iodine forms a variety of ions and com­pounds when added to drinking water(23,24). Recycling systems now beingplanned for long-term flight missions willlead to further iodine-eontaining by-prod­ucts. The bioavailability of these by-prod­ucts, and even their chemical identity, isnot known. Thus, biological monitoring isthe only means to determine tissue bur­dens of iodine.

The primary objective of this study wasto evaluate the usefulness of hair, saliva,and urine for biological monitoring ofiodine in order to establish guidelines for

assessing astronauts' exposure to iodine indrinking water. This was accomplished bystudying iodine elimination in human andin vivo iodine incorporation into humanhair, both in humans and in a humanhair/nude mouse model, after single-doseand prolonged exposure.

Material and MethodsWe monitored iodine in blood, saliva, urine,and hair in five patients with a diagnosis ofthyroid carcinoma. Four weeks after a totalthyroidectomy the patients received a thera­peutic, single oral dose of 150 mCi Na1311,carrier-free (Iodotope, Squibb Diagnostics,Princeton, New Jersey). Elimination ofiodine in blood, saliva, urine, and hair wasdetermined for 3 days duting hospitalizationand when available over the next week.During hospitalization, blood was collectedonce a day, saliva twice a day, and urinetwice a day in precise 2-hr collections (2 hrafter emptying the bladder), after obtainingwritten consent. We measured 131I using aPackard y-scintillation counter. Creatininelevels (Sigma, St. Louis, Missouri) weremeasured in urine. Comparison of meanhalf-time (tI/2) values of iodine eliminationin blood, saliva, and urine was performedusing the Hest. The relationship of iodineconcentration among blood, saliva, andurine was analyzed with Pearson's correla­tion coefficient, and pettinent j>-values werecalculated using linear regression. A j>-value<0.05 was considered statistically significant.

Iodine incorporation into hair was eval­uated using hairs plucked 2, 20, 24, 48, and52 hr after iodine administration. Hairswere processed for autoradiography withKodak X-OMAT film, exposed for 48 hr atroom temperature, and developed. To eval-

Address correspondence to G. Zareba, Depanmentof Dermatology, University of Rochester, MedicalCenter Box 697, Rochester, NY 14642 USA.We thank R.E. O'Mara, chair of the Depanment ofNuclear Medicine, University of Rochester. foraccess to iodine-treated patients, Kristi Pinman forexcellent technical assistance, and Robert Gelein forcreatinine analysis. This work is supported in partby grant NAGW-2356 to the NASA SpecializedCenter of Research and Training at the Universityof Rochester and by grant ES-01247 from theNational Institute of Environmental HeahhSciences.Received 27 December 1994; accepted 28 July1995.

1032 Volume 103, Number 11, November 1995 • Environmental Health Perspectives

Articles' Biological monitoring of iodine

Table 1. Iodine half-times (tIn; hrl in the blood,saliva, and urine of patients after a single, oraldose of 150 mCi 131 1

values, were calculated separately for allpatients (Table 2). Levels of iodine in vari­ous media were highly correlated. Meancorrelation coefficients (7) between iodineelimination in different media were forblood/saliva 0.99, blood/urine 0.95, andsaliva/urine 0.97. The small number ofcases did not allow us to obtain statisticalsignificance in all correlations (Table 2).

Comparison of elimination curves in theurine of one patient with or without creati­nine correction is shown in Figure 2. Theabsolute value of iodine concentrations inurine revealed marked variability, which wascorrected by adjusting for creatinine levels.

Although the rapid elimination did notallow us ro monitor iodine concentrationsin patknrs' hair over a long period of time,the autoradiographic studies ofhair demon­strated augmented accumulation of iodinein the hair roOt (Fig. 3). Repeared measure­ments over a 52-hr observation periodshowed an increase in iodine 131 1 uptakeinto the hair rOOt with time. Iodine was also

100,000

NC, not collected.

0.98'0.96'0.990.95'0.98'

Saliva/urine

0.98'NONO0.92'NO

Blood/urine

0.98'NO0.990.99NO

Blood/salivaPatient

NO, not determined.'Statistically significantlp<:0.051.

J.W.V.S.S.R.P.S.J.R.R.

Table 2. Correlation coefficient In for iodine elimi­nation in blood, saliva, and urine of patients aftera single, oral administration of 150 mCi 131 1

found along the hair shaft 52 hr after iodineadministration (Fig. 3), indicating externaliodine contamination of hair.

To study stability of iodine incorpora­tion into human hair, root hairs obtainedfrom 13lI-treated parients were washedwith ether, acetone, or I % detergent solu­tion (Fig. 4). Washing with ether and ace­tone did not change iodine concentrationsin the hair root, whereas soaking withdetergent solution removed the majority ofiodine (about 50%).

Auroradiographic studies of humanscalp nansplanted onto the nude mouseperformed 2 weeks after cessation of dailyexposure (NaI25[, 10 mg IIml, 100 flCi/mlfor I month) did nOt show iodine accumu­lation along the hair shaft (data nOt shown).

DiscussionAstronaurs consuming water disinfectedwith iodine must be monitored to preventthe occurrence of adverse health effects. To

Urine

15.78.4

17.416.613.4

14.3 ± 3.6

Saliva

18.312.013.410.714.0

13.7 ± 2.9

Blood

17.3NC

16.310.3NC

14.6 ± 3.8

Patient

J'w.V.S.S.R.P.S.J.R.R.Mean ± SO

uate stability of iodine incotporation, hairswere washed with acerone, ethyl ether, or1% nonionic detergent solution for I hr,rinsed three times with deionized water,and air dried. We measured iodine levelsafter the washing procedure as a percentageof initial concentration.

We used the human scalp/nude mousemodel to study incorporation of iodine intohair during continuous iodine exposure.Ten 5-week-old male BALB/c nu/nu nudemice obtained from NIH Taconic Farm(Germantown, Maryland) were housed inmetabolic cages in a clean room(bioBubble, Inc., Forr Collins, Colorado) ina 12-hr lightlI2-hr dark cycle ar 25'C withfree access to tap water and mouse chow(Purina Mills Inc., Richmond, Indiana).Human tissue collection conformed to cur­rent recommendations of the NationalInstirutes of Health and recommendationsof the University of Rochesrer's Commineeon Investigations Involving HumanSubjects. Human scalp skin grafts weretransplanted subcutaneously using pento­barbital for anesthesia (60 mf,/kg).

We administered Na'2 I (NaI, FisherScientific, Pittsburg, Pennsylvania; Nal25Icarrier-free, Dupont, Wilmington, Dela­ware) solutions to animals using subcuta­neously implanted ALZET osmotic pumps(model 2002; 10 mg IIml, 100 flCi/ml).Biopsies from grafts of human scalp andmouse skin were taken 2 weeks after cessa­tion of exposure, embedded in plastic, andprocessed for autoradiography with KodakNTB-2 film emulsion, exposed for 7 daysat 4'C, and developed. Secrions were thenstained with toluidine blue and mountedwith Permount (Fisher Scientific).

Figure 1. Elimination of 131 1in urine, saliva, and blood of patient J'w. within 3 days after a single, oral doseof 150 mCi 13'1.

t Urine _ Saliva

ResultsTable I shows half-time (t /2) values inblood, saliva, and urine of all patients.Mean t1/2 values were similar: in blood14.6 ± 3.8 hr, in saliva 13.7 ± 2.9 hr, andin urine 14.3 ± 3.6 hr (differences were notsratistically significant).

The iodine elimination in blood, urine,and saliva of patient ].W., administered asingle dose of 150 mCi 1311, is shown inFigure I. In the first 3 days, iodine in allpatients was eliminated in the highest con­cenuations in urine and saliva, showingfirst-order elimination. Levels of iodine inblood were about 30 times lower than insaliva and urine. Iodine concentrations insaliva were only slightly higher rhan inurine. Despite different magnitudes, thepanern of elimination was similar for allthree media.

Correlation coefficients between iodineelimination in blood and saliva, blood andurine, and saliva and urine, with relevant p-

10,000

E 1,000

'"'0:EE...u

100

10

10

• Blood I

20 30

hours

40 50 60

Environmental Health Perspectives, Volume 103, Number 11, November 1995 1033

Articles' Zareba et al.

• 1JI1in urine (cPnVml)

• IJ11in urine, corrected for creannineIcpmlmgcreatininel

120,llXI

100,000

80.000

J.Q

E 60.000

~u

".000

20.000

20 28 44 52 192

detergent

acetone

ether

%of iodine remaining

Figure 4. Removal of 131 1 from human hair afterwashing with ether, acetone, or 1% detergentsolution as a percentage of initial concentrationof 1311in unwashed hair {lOO%).

hours

Figure 2. Comparison of 1311elimination curves in urine of patient JW. after a single, oral dose of 150 mCi131 1. 2-hr urine collection.

Figure 3. Autoradiogram of hair of patient J.W. Iodine accumulation in hair roots increased after a singleadministration of 150 mCi 1311. Hair samples collected atlAI2 hr, 18120 hr, (C124 hr. 10144 hr, and (E152 hrafter iodine administration.

our knowledge, the usefulness of hair, sali­va, and urine for evaluaring human expo­sure ro iodine had nor been studied.

There are many conrroversial dara onuprake of iodine inro rhe hair follicle.Leblond (1:!) postulated that iodine in hairoccurs in inorganic form (iodide) and canbe related ro the iodine conrenr of the diet.Brown-Granr et al. (13,14) showed thatiodine in hair occurs at the site where initialstages of keratin formation take place andthat iodine incorporation can be associatedwith the binding ro sulfhydryl groups in theprekeratogenous zone of the hair roor.More recently, Jones et al. (25), after invitro iodination of wool fibets, found a highiodine conrent in the orthoconex of thewool shaft associated with ryrosine-rich pro­teins. Conrrary ro these findings, Wright(15) demonsrrated iodine incorporationinto the rat hair follicle in the region where

hair grows 0.3-0.4 mm per day, the label­ing over 9 mm in 3 days suggestS externalcontamination. The amount of iodine thatremains in hair could be due to incompletewashing. These results were further sup­ported by data obtained from our uniqueexperimental model, human hait growingon nude mice. Auroradiograms of humanhair after continuous, I-month exposure ofmice ro high doses of iodide did nor showiodine incorporation along hair shaft (datanot shown). A different medium thereforeshould be considered for biological moni­roring of iodine exposure in astronauts.

We found that high iodine concentra­tions in saliva parallel iodine excretion inurine and blood (Fig. I) and can provideinformation about the level of exposure, inagreemenr with other studies (21). Ifappropriate corrections are made for salivaflow rate (28), saliva should prove usefulfor biological monitoring of astronauts.Saliva has been shown ro be an excellenrbiological moniroring medium for aceta­minophen in astronauts (18).

Numerous srudies have shown thatdaily urine iodine excretion can be accept­ed as a satisfacrory index of iodine intake(4,5,21,2:!), but there are limited data oniodine concentrations after exposure to

excess iodine. Grasso et al. (29) reponedhigh concentrations (more than 1000 ~g

Ilg creatinine) of iodine in the urine ofpatients admitted ro the hospital fot non­thyroidal diseases. In the few reports oncontrolled human exposure ro excess iodinein drinking water (30,31), iodine concen­trations in urine exceeded 1000 ~g l/g cre­atinine. Philips et al. (3:!) reported thyro­roxicosis in England caused by high iodineconcenrrations in milk when cattle feedwas supplemented with iodine. Nelson etal. (33) demonstrated a strong correlationbetween urinary iodine excretion andiodine content of milk. A good correlationberween iodine dose administered to vol-

o

protein (keratin) formation is complete, atthe level of the sebaceous gland. These dataare supported by the observation of Abdel­Dayem et al. (17), who reported a singlecase ofa significant amount of 131 [ detectedalong the hair shaft of a Bedouin woman,scanned 7 days after the administration of50 mCi of 131 [ in a single therapeutic dose.This case indicates iodine contamination ofthe hair shaft from sweat or sebum. Bate etal. (26) noted that since many elements pre­sent in hair are also present in sweat, whichcomes into contact with hair, this externalcontamination may provide an "absorptiveorigin" for many elements found in hair.

Our data confirmed that in vivo iodinebinding ro the human hair root occursmostly on the surface of the hair and thatthe iodine detected should be consideredexternal contamination that can beremoved by washing (Fig. 4). Because the

BA

1034 Volume 103, Number 11, November 1995. Environmental Health Perspectives

Articles· Biological monitoring of iodine

unteers in drinking warer and urinaryiodine excretion was observed by Robinsonet al. (personal communication). Fromrhese repons and from our data, we con­clude that urinary iodine determinationsseem 10 be rhe mosr reliable biologicalindex of iodine exposure in humans.

It should be pointed out that there aresome conrroversies regarding rhe units inwhich iodine urinary excretion should beexpressed. Some data reported excrerionrelative to creatinine excretion, others onthe basis of 24-hr urine collection or iodideexcretion per kilogram body weight (22).Our data showed clearly that due 10 largevariations in iodine excretion. the assess­ment of iodine in urine should be adjustedfor creatinine excretion (Fig. 2).

It should be stressed that there are norecommendations for maximum safe con­cenrrations of iodine in urine associatedwith excessive iodine intake. According 10

recent repons of the Food and NuttitionBoatd of the National Academy ofSciences, a daily iodine inrake in adultsranging from 50 to 2000 fIg of iodine/dayhas no adverse effects in healthy individuals(21). Since NASA uses iodine concenrra­lions in drinking water of 2 mg/I (1), thedaily average intake can easily exceedacceptable values.

In summary, we conclude that hair can­not be used as a medium for biologicalmoniroring of iodine in humans. Salivaryiodine levels showed promising correlationwith the other media, and saliva has theadvanrage of offering noninvasive collec­tion in space. The established indicalOrthat can provide satisfaclOry informationabom exposure 10 iodine is urine, whenadjusted for creatinine, but more studies onthe relationship among urine levels, bodyconcenuations, and thyroid functionshould be d'llle to evaluate risk assessmenrof astronaut exposure related 10 iodine indrinking water.

REFERENCES

I. Sauer Ri, Janik OS, Thorstenson YR. Medicaleffects of iodine disinfection products in space­craft water. SAE rechnical report no. 871490.Warrendale. PA:Socicry of AutomotiveEngineers, 1987.

2. Bull RJ. Toxicological aspects of water recycle

and disinfection. SAE technical reporr no.871491. Warrendale, PA:Sociery of Auro­motive Engineers, 1987.

3. Silva JE. Effects of iodine and iodine-eontain·ing compounds on thyroid function. Med ClioN Am 69:881-898 (1985).

4. Standbury JB. Iodine. In: Modern nutrition inhealth and disease (Shils ME, Young YR, eds).Philadelphia, PA:Lea and Febiger,1988;227-237.

5. Pennington JAT. A review of iodine toxicityreportS. J Am Diet Assoc 90: 1571-1581(1990),

6. Woeber KA_ Iodine and thyroid disease, MedClin N Am 75:169-178 (1991).

7. Matsubara j. Machida K. Significance of e1e­memal analysis of hair as a means of detectingenvironmental pollution. Environ Res38:225-238 (1985).

8. Suzuki T. Hair and nails: advamages and pit­falls when used in biological monitoring. In:Biological monitoring of toxic metals (ClarksonlW, Friberg L, Nordberg GF, Sager PR, eds).New York:Plenum Press, 1989;623-640.

9. Cox C, Clarkson lW, Matsh DO, Amin-ZakiL, Tikriti S, Myers GG. Dose·response analysisof infants prenatally exposed to methyl mer­cury: an application of a single compartmentmodel to single-strand hair analysis. EnvironRes 49:318-332 (1989).

10. I<:ln SA, I<:ltl RB. Use of hait analysis for eval­uating mercury intoxication of the humanbody: a teview. J Appl Toxicol 12:79-84(1992).

II. Zarcba G, Goldsmith LA, Clatkson TW.Application of hair analysis fot biological moni­toring of toxic substances in space. SAE techni­cal report no. 932095. Warrendale, PA:SocieryofAutomotive Engineers. 1993.

12, Leblond CP_ Chemical form of the iodine pre­sent in the hair of the rat. Endocrinology54:104-107 (1954).

13. Brown-Grant K, Pethes G, Rogers AW. Thedistribution of radio-iodide in the skin of thetat. J PhysioI152:467-473 (1960).

14. Btown-Grant K, Pethes G. The uptake of 1311by the hair of the rat. J Physiol 152:474-481(1960).

15. Wright EA. The site of uplake of iodine byhair, Naunyn-Schmiedebetgs Arch Exp PatholPhartnakol 248:417-425 (1964).

16. Leder O. The significance of extrathyroidalradioactive iodine accumulation and secretionin clinical pathology. Histochemistry74:585-588 (1982).

17, Abdel-Dayem HM, Halker K, EI Sayed M,The radioactive wig in iodine·131 whole bodyimaging. Clin Nucl Med 9:454-455 (1984).

18, Putcha L, Pool SL, Cintron NM.Pharmacology. In: Space physiology and medi­cine (Nicogossian AE, Huntoon CL, Pool SL,eds). Philadelphia, PA:Lea and Febiget,1994;435-446.

19. Cohen B, Myant NB. Concentrarion of sali­vary iodide. a comparative swdy. J Physiol145:595-610 (1959).

20. MacFarlane S, Papadopoulos S, Harden RMeG, Alexander WO. 1-131 and MIT-I-131 inhuman urine, saliva and gastric juice: a compar·ison between eurnyroid and rhyroroxic patients.J Nucl Med 9:181-186.(1968).

21. NAS. Food and Nutrition Board.Recommended dietary allowances. 10th ed,Washington DC:National Academy Press,1989;213-217.

22. BrugJ, Lowik MRH, van Binsbergen Jj, OdinkJ, Egger RJ, Wedel M. Indicators of iodine sta­tUS among adults. Ann Nute Merab36:129-134 (1992).

23. Silverstein J, Hurst C, Batklwy R, Dunham A.Effect of iodine disinfectant source and waterquality parameters on soluble iodine speciation.23rd Intersocietal Conference onEnvironmental Systems, SAE technical paperno. 932096. Warrendale, PA: 1993.

24. Silverstein J, Brion GM, Dunham A, Hurst C,Todd P, Schulz J. Contaminant accumulationin space water recycle systems. ActaAstronautica 33:317-338 (1994).

25. Jones LN, Kaplin IJ, Legge GJF. Disttibutionsof protein moieties in a-keratin sections. JComp Assist Microsc 5:85-89 (1993),

26. Bate LC. Adsorption and elution of trace ele­ments on human hair. Int J Appl Radiat IsO!17:417-423 (1966),

27. Nishizawa K, Ohara K, Ohshima M, MaekoshiH. Orito T. Watanabe T. Monitoring of Iexcretions and used materials of patients treatedwith IJ'I. Health Phys 38:467-481 (1980),

28. Mason OK, Harden R MeG, Alexander WO.The influence of flow rate on the salivary iodideconcentration in man. Arch Oral Bioi11 :235-246 (1966).

29. Grasso L, Maxia PL, Barralena LV, MurtasML, Taberlet A, Manino E. Iodine conramina·tion in subjects admitted to a general hospital. JEndoerinol Invest 15: 307-308 (1992).

30. Freund G, Thomas WC, Bird ED, KinmanRN, Black AP. Effect of iodinated water sup­plies on thyroid function. J Clin EndocrinolMetab 26:619-624 (1966).

31. Li M, Liu DR, Qu CY, Zhang PY, Qian QD,Zhang CD, Jia QZ, Wang HX, Eastman CJ,Boyages SC, Collins JK, JupP JJ, Maberly GF.Endemic goitre in central China caused byexcessive iodine intake. Lancet ii:257-259(1987).

32. Phillips DIW, Nelson M, Barker DJP, MorrisJA, Wood TJ. Iodine in milk and the incidenceof thyrotoxicosis in England. Clin Endocrinol28: 61-66 (1988).

33. Nelson M, Phillips D1W, Morris JA, Wood TJ,Urinary iodine excretion correlates with milkiodine content in seven British towns. JEpidemiol Comm Health 42:72-75 (1987).

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1035

Environmental Urban Lead Exposure and Blood Lead Levels in Children ofMexico CityIsabelle Romieu,f Tania Carreon/ Lizbeth Lopez/ Eduardo Palazuelos,3 Camilo Rios,4 Yves Manuel,5 andMauricio Hernandez-AviiaZ'Centro Panamericano de Ecologia Humana y Salud, Organizacion Panamericana de la Salud, Mexico City, Mexico; lCentro deInvestigaciones en Salud Poblacional, Instituto Nacional de Salud Publica, Cuernavaca, Mexico; 3Hospital ABC, Mexico City, Mexico;"Instituto Nacional de Neurologia y Neurocirugia, Mexico City, Mexico; 'Environment Ministry, Paris, France

Lead contamination is now a leading public health problem in Mexico. However, there are fewdata on the lead content of various environmental sources, and little is known about the conui·bution of these sources to the total lead exposure in the population of children residing inMexico City. We conducted a cross-sectional study in a random sample of 200 children youngerthan 5 years of age who lived in one of [wo areas of Mexico City. Environmenral samples of

floof, window, and street dust, paint, soil, water, and glazed ceramics were obtained from the

participants' households, as well as blood samples and dirt from the hands of rhe children. Bloodlead levels ranged from 1 [0 31 ~g/dl wirh a mean of9.9 ~g1dl (SO 5.8 ~g1dl). Forty-four pec­cent of the children 18 months of age or older had blood lead levels exceeding 10 ~gldl. The leadcontent of environmental samples was low, except in glazed ceramic. The major predictors ofblood lead levels were the lead content of the glazed ceramics used to prepare children's food,exposure to airborne lead due to vehicular emission, and the lead content of the dirt from thechildren's hands. We conclude that the major sources of lead exposure in Mexico City could becontrolled by adequate public health programs to reinforce the use of unleaded gasoline and toencourage production and use of unleaded cookware instead of lead-glazed ceramics. Key words:glazed ceramics, lead, Mexico City, vehicular emissions. Environ Health Perspect 103: 1036-1 040(1995)

Already the second most populated city inthe wotld, Mexico City will enter the twen­ty-first centuty with nearly 5 million moreinhabitants than it had in 1991. This kindof gtow[h comes at a high price.Environmental pollution is one of the city'sleading public health problems, and this isgreatly exacerbated by rapid urban growthand continued use of inappropriate produc­tion and control technology.

Exposure to lead is a major concern.Even ar low blood levcis, potential adversehealth effects have been observed. Severalepidemiologic studies have reported bloodlead levels and risk factors for the popula­tion of Mexico City (1-7). However, infor­marion is scarce about the concentration oflead in the environment and the contribu­tion of various sources to total lead expo­sure in the population of Mexico City. Thisknowledge gap must be closed so thar ade­quate control measures to decrease leadexposure in the general population can beapplied. Because sources of lead exposuremay vaty widely according to the area ofresidence and also by age (given that chil­dren have different habits from adults), weconducted a cross-sectional study to derer­mine the contribution of various environ­mental media to the blood lead levels inwomen of reproductive age (15-48 years)and their children younger than 5 years ofage. In this report, we address the impact ofenvironmental lead exposure on children'sblood lead levels.

Methods

Study population. The population studiedwas composed of women of reproductiveage (15-48 years) and their childrenyounger than 5 years of age. The subjecrslivied in the southern pan of Mexico City(Tlalpan) or in a more northern area(Xa1ostoc). These two areas were selectedbecause we expected the major sources oflead exposure to differ: Tlalpan is mostly aresidential area, and XalOStOC is locatedwithin the industrial pan ofMexico City.

In each area, a random sample of 250households was selected. All houses werevisited to obtain a sample size of 100 pairs(mother-child). Selected women wereinvited to participate in the srudy, whichincluded the completion ofa questionnaire,environmental sampling of their household,and collection of blood samples from eachwoman and her child. Participants wereinformed of the study objectives and askedto sign an informed consent form.Sampling procedures were conducted fromOctober 1992 to June 1993. Additionalenvironmental monitoring of street dustwas conducted from May to June 1994.After all data were collected, dietary coun­sciing and advice to minimize lead exposurewas provided to all panicipants.

Environmental samples. Environ­mental sampling procedures for soil, dust,paint, and water were carried out in accor­dance with the technique proposed by the

Environmental Sciences and TechnologyLaboratory, Georgia Technical ResearchInstitute (Atlanta, Georgia) and recom­mended by the U.S. Department ofHousing and Urban Development (8).Training of the field personnel and stan­dardization of procedures were provided bya senior scientist from the GeorgiaTechnical Institute. All procedures werecarried out using vinyl gloves.

Composite soil samples were obtainedfrom various places close to each partici­pant's house (yard, front door, children'splay area, place where rain water drainsfrom the roof). These samples wereobrained from superficial soil, using aspoon [hat was cleaned between collectionof each sample. Five subsamples were rakenin each area. All were collecred in plasticcontainers with hermetic lids.

We used two techniques to collect inte­rior dust samples. 1) Dust was collectedfrom carpeting and furniture with a person­al monitoring pump (2.5 I/min) connectedto a two-piece air monitoring cassette witha 0.8-~g cellulose ester filter (37 min).Several samples (30 cm 2 each) wereobtained. All personal monitoring pumpswere calibrated on a daily basis before fieldwork. 2) Samples were obtained from floorsand window sills using moist wipes (K­Mart "Little Ones"). The sample area waswiped three times in an "S" partern, whilettying to achieve 100% coverage over a sur-

Address correspondence to M. Hernandct-Avila,Instituto Nacional de Salud Publica, AvUniversidad 655, Col Sta Maria Ahuacatidan,Cuernavaca, Morelos, Mexico.This study was supported by funding from theFundacion Mexicana para la Salud. the ConsejoNacional para la Ciencia y la Tecnologia, TheAmerican British Cowdray Hospital, The ConsejoAsesor en Epidemiologia. the French MiniS[ry ofEnvironment, and the National Center forEnvironment, Centers for Disease Control andPrevention. We thank David Jacobs. GeorgiaTechnical Institute. for training field personnel andstandardizing procedures; Tito Alexandre and all ofthe health professionals who panicipated in the fieldwork; Magdalene Rojas for the laboratory analysisof glazed ceramic samples; the National Institute ofOccupational Safety and Health and the WisconsinOccupational Health Laboratory for providing thefilters for dust analysis; and Jane A. Zanca for assis­tance in preparing the manuscript.Received 13 March 1995, accepred 3 August 1995.

1036 Volume 103, Number II, November 1995. Environmental Health Perspectives

Articles' Environmental lead exposure in Mexico City

face of at least 30 cm2 Each wipe wasplaced in a 100-ml plastic tube with a het­metic lid. Sampling was conducted in theliving toom, the kitchen, the childten'sroom, and the parents' room. A similartechnique was used to sample the dirt onthe childten's hands. Street dust was col­lected using a small btoom ovet an atea ofI m2 and sealed in a plastic container withhetmetic lid.

We tested fot lead in paint using a XK­3 (Ptinceton Gamma Tech, Princeron,New Jersey) instrument. The instrumentwas calibtated at the beginning of eachwotk petiod and duting usage. Quick cali­btation checks wete made accotding to theprotocol fot quality control of field mea­sutements made with X-tay fluotescence(XRF) instruments. Thtee teadings weteobtained ovet a selected atea and the atith­metic mean was calculated. Fot tesultsberween 0.5 and 1.5 mglcm2, paint chipswete obtained ovet an atea of at least 4 cm2

and kept in a plastic bag.Watet samples wete obtained in 250-ml

plastic containers ptewashed with 5% nitricacid. To obtain samples of pH equal to 2.0,2 ml of nitric acid was added to the con­tainer. At the time of the household visit,samples were obtained from the kitchenfaucet as well as from watet Stored fordrinking or cooking pUtposes. Participantsusing low-temperature lead-glazed ceramicware to cook Ot stOte foods wete asked toprovide the cookwate for analysis. A Steelpan was offeted in exchange. Atmospheticlead levels wete provided by the monitotingnerwotk of Mexico City (monitoting Sta­tions in Tlalpan and Xalostoc).

All laboratoty analyses were conductedusing atomic absotption spectrophotome­try. Labotatoty analysis fot lead in soil,dust, and paint was conducted by the HESLabotatory (CharleSton, South Carolina).Laboratory analyses for lead in watet weteconducted using a Perkin Elmer 3000instrument by the ABC HospitalLaboratory, Mexico City, Mexico. Ceramicware lead analyses were conducted at thelaboratory of the National Institute ofNeurology and Neurosurgery, MexicoCity, Mexico. All laboratories had internaland external quality controls. Efforts weremade to obtain environmental samplesfrom each participating household. Insome cases (for example, if the house wasnot painted), specific environmental sam­ples could not be obtained.

Blood samples. Venipuncture bloodsamples were obtained from each pair(mother-ehild) in their household, collect­ed in lead-free tubes by a trained pediatricnurse. Blood samples were analyzed byaromic absorption spectrophorometry

(Perkin Elmer 3000) by a standardized lab­oratory (ABC Hospital Laboratory).External quality control was provided bythe Centers for Disease Control andPrevention Labotatoty (Atlanta, Georgia).Blood lead measurements were reported inmicrograms per deciliter (1 flg/dl =0.0484flmolll).

Statistical analysis. The statisticalanalyses included environmental data col­lected in 200 households (100 in thesouthwest part of the city and 100 in thenortheast part of the city) and the bloodlead levels of children living in these house­holds. In many households, we obtainedseveral samples of soil, dust, and paint ftomvarious areas of the house. The lead con­tents of specific samples were averaged, andthe median was used in the analyses. Weanalyzed the data fitst using environmentalsamples with detectable levels of lead andsecond including samples below the detec­tion limit, assuming a value of 0.5 of thedetection limit for these samples. Resultswere similar using borh methods. In theresults we present only those includingsamples with complete information. Tocombine the rwo types of lead paint mea­surements (XRF and wet chemistry), weused the ordinal scale ptoposed byRabinowitz et al (9). A score of 0 corre­sponded to <0.5% lead by wet chemistty or<0.4 mg/cm2 by XRF. Similarly, a score of1 cotresponded to 0.5-1.5% lead by wetchemistty or 0.5-1.5 mglcm2, and so on toa score of 10, which was assigned to anyvalue equal to or greater than 10% or 10mg/cm2

To analyze the impact of lead-glazedceramics on the children's blood lead levels,we created a new variable thar combinedthe questionnaire response on the use oflead-glazed ceramics to prepare or srorechildren's food and the measurements oflead leached from the ceramic wareobtained from the participating house­holds. When the mother teported notusing lead-glazed ceramics ro prepare herchild's food, the value assigned to the vari­able was O. Otherwise we assigned thevalue of lead leached by the ceramic wareftom the cotresponding household.

To determine the correlarion berweenatmospheric lead and other environmentalvariables, we used the lead content of par­ticulates on the sampling date of each spe­cific household. Since measurements ofatmospheric lead were performed onlyevety 6 days, the value was assigned for thedate of the air sampling, 2 days before, and3 days after the monitoring day. To deter­mine the correlation berween children'sblood lead and atmospheric lead, we aver­aged monitoring data over the 3 months

before blood sampling, thus establishing abetrer estimate of children's exposure.

To determine the socioeconomic levelof the participants, we used an adaptationof the socioeconomic index developed byBronfman et al. (J(J). This index has beenwidely used in Mexico and has been provento discriminate social strata very well.Because the distribution of blood lead lev­els was skewed, we used the log-trans­formed value of blood lead levels in allanalyses. To determine the relation ofblood lead levels and environmental mea­suremems, we used correlation coefficientsand linear regression analysis accountingfor porential confounding variables (11).Chi-square value due to linear regressionwas used for the significance of the lineartrend. All analyses were performed usingSAS software (Cary, North Carolina) (12).

ResultsThe average blood level among the 200children participating in the study was 9.9flg/dl (SO 5.8 flg/dl; range 1-31 flg/dl).Table 1 presents the mean blood levelsaccording to age groups and areas of resi­dence. Blood lead levels were slightly high­er in children in the industrial area ofXalostoc than children in the residentialarea of Tlalpan (mean 10.5, SO 5.5 flg/dlversus mean 9.4, SO 6.0 flg/dl, respective­ly). This was observed in all age groups. Asshown in Table I, in both areas there wasan increase in the blood lead level of chil­dren between the ages <18 months and18-35 months (p = 0.02 in Tlalpan and p= 0.15 in Xalosroc), and a significantincreasing trend in blood lead levels wasobserved with increasing age in both areas(p =0.0035); older children tended to havehigher blood lead levels than younger ones.Among the children ~18 months of age,52% had blood lead levels exceeding 10flg/dl in Xalostoc vetsUS 36% in Tlalpan (p= 0.05).

Lead concentrations in the environ­mental samples are presented in Table 2.Most of the lead levels in indoor dust werelow, and only a few samples exceeded theguidelines of the U.S. Department ofHousing and Urban Development (13).The highest indoor lead levels wereobserved in dust samples from windowsills: 7.1 % of these samples exceeded 0.215flg/cm2 of lead content (corresponding to200 flglft2). Residential soil samples had alow lead content. Only 6% of these sam­ples exceeded a lead content of 200 ppm;one soil sample exceeded a lead content of500 ppm. In comparison, lead concentra­tions in street dust were high, with 44.5%of the street dust samples exceeding a leadcontent of 200 ppm and 7.5% exceeding

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1037

Articles' Romieu et al.

Tabl. 1. Blood lead levels I~g/dll in relation to age and study area, Mexico City, 1993'

Xalostoc Tlalpan Total

Age n x SO %>10 ~g/dl x SO %>10 ~g/dl x SO %>10 ~g/dl

<18 months 27 7.89 4.53 25.9 25 6.82 5.13 20 52 7.38 4.81 23.1~18-35 months 30 10.93 6.77 46.7 25 9.17 4.67 28 55 10.13 5.92 38.2~3!;-49 months 22 11.86 4.19 54.5 22 10.27 7.13 31.8 44 11.07 5.83 38.2~50 months 21 11.59 5.04 57.1 28 11.26 6.33 46.4 49 11.40 5.76 51.0Total 100 10.45 5.50 45.0 100 9.40 6.02 32.0 200 9.91 5.78 38.5

'Significant increasing trend of blood lead levels with age was observed in both areas Ip<O.04)

Tabl.3. Spearman correlation between different environmental lead measurements, Mexico City,1993-1994

Floor Carpet Furniture Windowsill Street HandSample dust dust dust dust Soil dust dirt

Air lead 0.08 0.15 0.18 0.32- 0.16 0.21- 0.28-Bare-floor dust 0.41- 0.Jg- 0.11 0.30" 0.05 0.15Carpet dust 0.45" 0.55- 0.34 0.30* 0.10Furniture dust 0.06 0.15 -0.008 0.0005Window sill dust 0.21 0.01 0.21"Soil 0.41- 0.26"Street dust 0.15Hand dirt 1.00

"p~0.05.

-p~O.01.

'Only samples with detectable levels of lead are included.blnterquartile range 25%-75%.cStandard guideline =0.01 ppm.'The Mexican norm has been established at <75 ppm for 1994 and ~25 ppm for 1996.'Paint score is the combination of X-ray fluorescence and wet chemistry.'l4-hr average.

Tabl.2. Environmental lead measurements, Mexico City, 1993-1994observed, wirh a maximum of 2.41 ~glm3

(24-hr average). Over rhe srudy period,armospheric lead levels were significanrlyhigher in Xalosroc rhen in Tlalpan (p =

0.001).The lead levels in indoor dust on bare

(nor carpered) floor, carpeted floor, furni­rure, and window sills were posirively cor­related (Table 3). Soil and Street dust werealso positively correlated. Atmospheric aitlead levels were correlated with furnitureand window sill dust lead and street dustlead. There was a positive correlationberween the amounr of lead collected onchildren's hands and atmospheric lead, aswell as indoor dust lead coUected on floorsand window sills. The highest correlationwas observed with the lead conrenr of win­dow sill dusr samples (r = 0.21, P = 0.07)(Table 3). Residenrial soil and street dustlead COnrenrs were also positively cotrelatedwith the lead content of dirt on children'shands.

We observed a positive correlationberween children's blood lead levels andthe lead contenr of glazed ceramic wareused to prepare food (Table 4; r= 0.24, p =0.002). None of the orher environmenrallead measurements were significantly corre­lated to the children's blood lead levels.Atmospheric lead was only marginallyrelared ro blood lead levels (r = 0.11, P=0.14). However, we observed a significanrcorrelation berween the lead conrenr of thedirt on children's hands and their bloodlead levels (r= 0.19, p =0.025).

We then derermined the major predic­tors of children's blood lead levels. Age wassignificanrly related to children's blood leadlevels, but socioeconomic level and hous­ing location were not. Blood lead levelstended to increase with the inrensiry of therraffic close to the children's homes and theamounr of armospheric lead measured overthe 3 monrhs before blood sampling.Children who ate food prepared in lead­glazed ceramic had significanrly higherblood lead rhan their counrerpans. Finally,blood lead levels increased with the leadconrenr ofdirt from children's hands.

When we included these variables in amultivariate model, the only variables rhat

0.00~.024

0.002-ll.0080.00H.0070.02-ll.1O89.5-27030-1042.ll-4.6

0.0016-ll.0042230-35590.8-1.0

0.20-0.52

SO

0.080.0070.0030.19182.1305.22.260.00316860.600.59

likely ro conrain lead rhan warer-basedpainr (69% versus 16.7%). We alsoobrained addirional painr-chip samples (n =46) from some homes wirhour prior XRFscreening. Among rhese, 28% (n = 13)exceeded 5000 ppm.

We obrained 54 samples of lead-glazedceramic ware from rhe households enrolledin rhe srudy. Among rhese, 81% leached aquanriry of lead rhar exceeded rhe Mexicannorm of7 ppm (14). The quanriry of leadleached ranged from 0.05 ro 4968 ppm(mean 2163.3 ppm). The lead conrenr ofall warer samples were well below WorldHealrh Organizarion srandard guidelines(15J.

Over rhe srudy period, the meanatmospheric lead level did not exceed 1.5~g/m3. However, some exrreme values were

0.030.0060.0090.11205.6117.23.450.00421631.020.54

500 ppm. Comparing rhe areas of Tlalpanand Xalosroc, we observed rhar rhe leadcontent of soil and window sills was onaverage significanrly higher in Xalosroc (p =0.013 and p =0.010, respecrively).

Lead in residential paint was also low,and mosr of rhe XRF measurements fellwirhin rhe "inconclusive" range (0.5-1.4mg/cm 2). Among 419 measuremenrs,61.1 % (n = 256) were inconclusive andonly 10% (n = 42) were classified as posi­rive for lead conrenr (> 1.6 mg/cm2). Fromrhose samples wirh inconclusive lead con­renr by XRF measuremenr (>0.5 mg/cm2

and <1.6 mglcm2), we obrained 66 (21%)painr-chip samples for laborarory analysis.Thirry-rhree samples (50%) exceeded 5000ppm. However, we noriced rhar samples ofoil-based painr were significanrly more

Bare-floor dust 1~g/cm21 169Carpet dust 1~g/cm21 53Furniture dust 1~g/cm21 70Window sill dust (~g/cm21 104Street dust Ippml 200Soillppml 66Hand dirt I~g/subjectl 139Water Ippml' 195Lead in ceramic ware Ippmld 54Paint score' 128Air lead 1~g/m3If 200

Type of sample' n

1038 Volume 103, Number II, November 1995 • Environmental Health Perspectives

Articfes • Environmental lead exposure in Mexico City

Table 5. Regression analysis between children's blood lead levels and environmental variables and age,Mexico City, 1993'

'Blood lead is log transformed. The multivariate regression model explained 18.8% IR2) of the variability ofthe children's blood lead levels."Log transformed; measured in ppm.'Reference is low traffic score.dLog transformed; average over 3months before blood sampling, measured in ~g/m3.'Aeference is Tlalpan.

Univariate Multivariate

Variable B SE p R21%1 B SE p

Hand dirt 0.060 0.024 0.014 4.3 0.05 0.02 0.034Lead gla2ed ceramicb 0.147 0.050 0.004 4.1 0.17 0.05 0.003Traffic scorec 0.308 0.128 0.017 2.8 0.33 0.13 0.021Airbone leadd 0.213 0.049 0.000 8.5 0.150 0.06 0.015Living areae 0.145 0.091 0.111 1.2 0.04 0.11 0.717Age Imonthsl 0.0146 0.007 0.039 2.1 0.003 0.008 0.652

remained significanr were rhe lead conrentof the ceramic ware used ro prepare food,rhe inrensiry of traffic (rraffic score) closero children's home, the amounr of atmos­pheric lead measured over the 3 monrhsbefore blood sampling, and the lead con­tenr of dirt from children's hands (Table5). Our model explained 18.8% of thevariability of the children's blood lead(Table 5). When we stratified the data byage groups, we noted that among youngerchildren (25 months or younger), themajor predicrors of blood lead levels werethe intensity of the traffic close to thehouse (F = 3.85, P = 0.06), and the lead

. conrenr of dirt from children's hands (F =2.58, P=0.11). Among children older than25 monrhs, the major predictors were theuse oflead-glazed ceramic cookware to pre­pare the child's food (F = 5.76, P = 0.02),the vehicular traffic close ro the household(F = 5.49, P =0.02), and the lead conrenrof dirt from hands dirt (F = 4.76, P =0.03).

DiscussionThis is the first large cross-sectional studyto evaluate the lead content of various envi­ronmental samples in Mexico City.Environmenrallead levels were low, except

Table 4. Spearman correlation between children'sblood lead levels and environmental variables

Variable R P

Floor dust ·0.03 0.73Carpet dust 0.18 0.19Window sill dust 0.07 0.47Furniture dust -0.15 0.23Street dust 0.04 0.55Soil ·0.04 0.73Air lead 0.11 0.14Air lead, 3-months' 0.30 0.000Hand dirt 0.19 0.025lead in ceramic ware 0.24 0.002Paint score ·0.08 0.36

'Average over 3 months before blood sampling,measured in ~g/m3.

for the lead conrenr leached from glazedceramic ware. We found that lead levels insuch cookware greatly exceeded theMexican norm for the lead content ofceramic ware (J4).

Children's blood lead levels were simi­lar in the twO areas of the study but wereslightly higher among children living inXalostoc, an industrialized area, in each agegroup. We also observed that the lead con­tenr of environmenral samples was higherin Xalosroc, especially for soil, window sill,and air. The major predictors of blood leadlevels were the use of lead-glazed ceramic toprepare or srore the child's food, lead frommotor vehicular emissions, and the leadconrent ofdirt from children's hands.

These results confirm that the use oflead-glazed ceramic is a major source oflead exposure (even among young chil­dren), and that airborne lead, mainly frommotor vehicular traffic, also plays animportanr role as a determinanr of chil­dren's blood lead levels.

Compared with results from studiesconducted in the United States (9,16-18),we did not observe high lead levels in resi­denrial painr, and there was no associationbetween blood lead levels and painr leadscores. The main source of indoor leadseemed to be related ro atmospheric leadlevels. Leaded fuel is still used in Mexico,and lead accumulates indoors, especially onwindow sills, which are not cleaned as fre­quently as floors. The lead conrenr of thestreet dust samples was higher than in theother environmenral dust samples. Theselevels were not correlated with the chil­dren's blood lead, probably because chil­dren of the age groups included in thesrudy were more likely ro stay at home.

We observed a positive correlationbetween lead in dirt from hands and bloodlead levels. Lead levels in hand dirt werecorrelated with indoor dust lead conrenr(floor and window sill); therefore, lead lev­els in hand dirt could be considered as a

proxy for lead exposure from householddust. Among younger children (25 monrhsor younger), hand dirt was an importanrpredictor of blood lead levels. This is notsurprising, since younger children are morelikely to have pica habits and to crawl onthe floor. Street traffic density near thehouse, as well as the three-monrh averageatmospheric lead levels before blood sam­pling, were related to blood lead levels.These two factors emphasize the impor­tance of the lead emitred in the atmos­phere, by both mobile and fixed sources, tochildren's lead exposure.

[n accordance with other studies con­ducted in Mexico, we observed that the useof lead-glazed ceramic to prepare and srorefood (3-6) was a major determinant ofchildren's blood lead levels. In this study,however, we quantified the relationbetween rhe amounr of lead leached fromthe ceramic ware and the blood lead levelsof children and confirmed the importanceof this source of lead exposure among chil­dren.

We were not able to measure the leadcontent of other potential sources of leadexposure, such as children's toys. As recent­ly as 1994, it was reported that, in Mexico,the paint used to cover some toys andschool equipment has a high lead content(5). Certainly, this could have contributedto the blood lead levels in the popularionstudied. A recently established standardregulates the use of leaded paint for chil­dren's toys; however, until industry com­pliance is ensured and umil items manufac­tured before the standard are phased out,srudies to assess and monitor blood leadlevels will be essential to the public'shealth.

All environmental samples in this studywere obtained following a standardizedprotocol, and our technicians were trainedby a senior scientist from GeorgiaTechnical Institute. We believe that thelead levels observed in this study are accu­rate and that environmental indoor leadlevels in households of Mexico Ciry are, onaverage, low. Households were selected atrandom afrer census of the two study areas;therefore, our findings can be inferred tothe general population of these areas,except for households located close to fixedsources of lead exposure (such as batteryrecycling shops).

We believe that our results are of greatpublic health relevance. Using the quanti­tative assessment of the lead content ofenvironmental media that we have provid­ed, it is possible to reduce blood lead levelsamong children by focusing on the majorsources of exposure. Environmental lead inMexico Ciry could be controlled by ade-

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1039

Articles· Romieu et al.

quate public health plOgrams to reinfotcethe use of unleaded gasoline and to imple­ment the production and use of unleadedcookware. An important element of theseptograms is an informed population.Parents who know the potential sources oflead exposure can and likely will act todectease exposure by regularly washingyounger childten's hands, teaching olderchildren to wash their hands often, andavoiding the use of lead-glazed ceramicware to prepare or store food.

REFERENCES

1. Hernandez Avila M, Ramieu I. Rios C. RiveroA. Palazue10s E. Lead-glazed ceramics as majordeterminants of blood lead levels in Mexicanwomen. Environ Health Perspecr 94:117-120(1991).

2. Albert LA, Badillo F. Environmental lead inMexico. Rev Environ Contam Taxicol 117:1-49 (1991).

3. Ramieu I, Palazue10s E, Meneses F, HernandezAvila M. Vehicular traffic as a determinant ofchildren's blood lead levels: a pilot study inMexico Ciry. Arch Environ Health47:246-249 (1992).

4. Jimenez. C, Ramieu I, Palazuelos E, Munoz I,Cones M, Rivero A, Catalan J. Facrofes de

exposicion ambiental y concenrraciones deplamo en sangre en ninos de la Ciudad deMexico. Salud Publica Mex 35: 599-606(1993).

5. Ramieu I, Palazuelos E, Hernandez Avila M,Rios C, Munoz I, jimenez C, Cahero G.Sources of lead in Mexico City. Environ HealthPerspeet 102: 384-389 (1994).

6. Rothenberg SJ, Perez Guerrero lA, Perroni·Hernandez E, Schnaas·Arrieta L, Casino-OrtizS, Suro-Carcamo M, Flores-Ortega j,Karchmer S. Fuentes de plomo en embarazadasde la cuenca de Mexico. Salud Publica Mex 32:632 --643 (1990).

7. Lara-Flores E. A1agon-Cano J, Bobadilla JL,Hernandez Prad B, Cisco man Begona A.Faccores asociados a los niveles de ploroo ensangre en residenres de la Ciudad de Mexico.Salud Publica Mex 31: 652-..Q33 (1989).

8. Georgia Technical Research Insticute. Lead­based paint detection and abatement. Atlanta,GA:Environmenral Sciences and TechnologyLaboratory, Georgia Technical ResearchInstitute, 1992.

9. Rabinowitz M, Leviton A, Needleman H,Bellinger D, Waternaux C. Environmental cor·relates of infant blood lead levels in Boston.Environ Res 38:96-107 (1985).

10. Bronfman M, Guiscafre H, Castro V, GutierrezG. II. Medicion de la desigualdad: Una estrate­gia merodologica. Analysis de las caracteristicassocioeconomicas de la muestra. Arch Invest

Call for Papers

Med (Mex) 19:351-360 (1988).11. Snedecor GW, Cochtan WG. Statistical meth­

ods. Ames, IA:lowa State University Press,1980.

12. SAS Institute. SAS language guide, release 6.03.Cary, NC:SAS Institute, 1988.

13. HUD. Lead-based paint: interim guidelines forhazard identification and abatement in publicand Indian housing. Washington DC:U.S.Department of Housing and UrbanDevelopment, 1990.

14. Diario Oficial Mexicano, CDLXXXII (120),NOM-Ol1-SSA1-1993. Mexico City:Gobierno constitucional de los £Stados UnidosMexicanos. 1993.

15. WHO. Revision of the WHO guidelines fordrinking water quality. Report of the final [askgroup meeting. Geneva:World HealthOrganization, 1992.

16. Sayre J, Charney E. Vostal J. Pless D. Houseand hand dust as a potential source of child~

hood lead exposure. Am J Dis Child127:167-179 (1974).

17. Clark S, Bornschein R, Succop P, Roda S,Peace B. Urban lead exposure of children inCincinnati, Ohio. Chern Spec Bioavail3:163-171 (1991).

18. Gilber C. Tuthill RW, Calabrese EJ, PerersHA. A comparison of lead hazards in the hous­ing environment of lead poisoned children ver·sus non-poisoned concrols. j Environ SciHealth 14:145-168 (1979).

International Symposium on EnvironmentalBiomonitoring and Specimen Banking

December 17-22, 1995 Honolulu, Hawaii, USA

This symposium is being held as part of the International Chemical Congress of Pacific Basin Societies (PACIFICHEM 95),sponsored by the American Chemical Society, Canadian Society for Chemistry, Chemical Society of Japan, New ZealandInstitute of Chemistry and the Royal Australian Chemical Institute.

Papers for oral and poster presentations are solicited on topics that will focus on: monitoring of organic pollutants; monitor­ing or trace metal pollutants; exposure assessment; and biomarkers and risk assessment/management. The deadline forreceipt of abstracts on the official Pacifichem 95 abstract fonn is March 31, 1995.

For further infonnation and abstract fonns, please contact:

K.S. Subramanian, Environmental Health Directorate, Health Canada, Tunney's Pasture,Ottawa, Ontario KIA 01.2, Canada (Phone: 613-957-1874; Fax: 613-941-4545)

or G.V. Iyengar, Center for Analytical Chemistry, Room 235, B125, National Institute of Standards and Technology,Gaithersburg, MD 20899, USA (Phone: 301-975-6284; Fax: 301-921-9847)

or M. Morita, Division of Chemistry and Physics, National Institute for Environmental Studies,Japan Environmental agency, Yatabe-Machi, Tsukuba, Ibaraki, 305 Japan(Phone: 81-298-51-6111 ext. 260; Fax: 81-298-56-4678).

1040 Volume 103, Number 11, November 1995· Environmental Health Perspectives

Third Annual Conference on

Exploiting Molecular Diversity:Small Molecule Libraries for Drug Discovery

January 29-31,1996, San Diego, California

The use of combinatorial libraries has rapidly moved from curiosity to a fundamental technique thatis revolutionizing high throughput screening for drug discovery. The technology addresses a prima­

ry bottleneck, which has been a limitation on the available diversity of compounds to be screened.Further progress is still needed to expand diversity and to optimize strategies for identifying new leadsand analogs of current leads. The progress of programs at many of the leading firms using combinatori­allibraries, as well as innovations by various newer entrants into the field, will be presented. The thirdday of the meeting will feature targets and resulting compounds being developed by pharmaceuticaland biotechnology end users.

For Information, contact:Mary Chitty, Cambridge Healthtech Institute

1037 Chestnut StreetNewton Upper Falls, MA 02164(617) 630-1300 FAX: (617) 1325

Advance Registration Deadline: 12/8/95Poster Deadline 1/5/96

Second Annual Genetic Screening & Diagnosisof Human Diseases

March 7-8, 1996, San Francisco, California

The sequencing effort of the Human Genome Project is complementing and simplifying efforts ofpositional cloning, leading to a dramatic rise in the number of genes identified for inherited disorders,

as well as genes and mutations that may predispose an individual to greater risk of other more com­mon diseases.The technology for detection of such genes and mutations, as well as some of the very

powerful implications of screening the genetic makeup of individuals, will be covered. Reports onefforts related to the identification and detection of genes and mutations for specific diseases, includ­ing cancers,Alzheimer's disease, and cardiovascular disorders, will be featured on the second day.

Advance Registration Deadline: 1/19/96

Poster Deadline 2/2/96For Information, contact

Mary ChittyCambridge Healthtech Institute

1037 Chestnut StreetNewton Upper Falls. MA 02164

(617) 630-1300FAX: (617) 1325

Potential for Bias in Epidemiologic Studies That Rely on Glass-basedRetrospective Assessment of RadonC.R. Weinberg

National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709 USA

Retrospective assessment of exposure to radon remains the greatest challenge in epidemiologicefforts to assess lung cancer risk associated with residential exposure. An innovative techniquebased on measurement of a-emitting, long-lived daughters embedded by recoil into household

glass may one day provide improved radon dosimetry. Particulate air pollution is known, howev­

er, to retard the plate-out of radon daughters. This would be expected to result in a differential

effect on dosimetry, where the calibration curve relating the actual historical radon exposure tothe remaining a-activiry in the glass would be different in historically smoky and nonsmoky

environments. The resulting "measurement confounding" can distort inferences about the effectof radon and can also produce spurious evidence for synergism between radon exposure and ciga­

rette smoking. Key wordr. bias, cigarette smoking, confounding, dosimetry, epidemiologic meth­

ods, passive smoking, radon. Environ Henlth Pmpect 103:1042-1046 (1995)

Radon is a noble gas formed as pan of theradioactive decay chain of radium, whichoccurs narurally in the earth's crust. It seepsthrough the soil and accumulates in build­ings, panicularly if the strucrure has cracksbeneath it and is tightly consrructed to beenergy efficient. Radon decays with a half­life of 3.8 days and forms radioactive lead,bismuth, and polonium"daughters" (Fig. I)that can attach and emit a-radiation, pene­trating the surfaces of the respiratory tract.

Dara from underground miners whowere occupationally exposed to high levelsof radon show evidence of the carcinogenic­ity of radon (more precisely, of radondaughters) to the lung (1). The evidence fordeleterious effects at rhe lower levelsencountered in rhe typical home has beenunconvincing (2-5), though such risk ishighly plausible.

A number ofcase-<:ontrol srudies of resi­dential radon exposure have been undenak­en. The rerrospective assessment of exposurerequires the placement of long-term (usuallyyear-long) radon measurement devices ineach home in which the srudy participanthas lived. The esrimated house-specificexposures must then be combined, e.g.,through integrating or averaging, for riskmodeling. Such srudies are highly laborintensive, and daunting practical difficultiesarise. The residential histories provided bythe study participant, including years ofoccupancy, must be verified, and the currentoccupant must agree ro have detectorsplaced in the home. In some cases the housemay not exist any more, the street may havebeen renamed or renumbered, or the housemay have been structurally modified to thepoint where the relevance of the currentradon levels to the levels formerly encoun­tered by the study participant is dubious.There is also considerable room for mismea-

surement because oflifestyle differences; forexample, the current occupant may sleepwith a window open, whereas the studypanicipant did not. Missing measurements,leading to large gaps in the reconstructedexposure histories are unavoidable, panicu­larly in a residentially mobile populationsuch as the United States. Experience incarrying out these difficult retrospectiveexposure asssessments shows that radonmeasurements can be made for about 70%ofstudy homes.

A recent breakthrough (6,7) couldpotentially both simplilY and improve the.retrospective assessment of residentialradon exposure. The method makes use ofglass objects that the study participantoriginally bought new and has taken fromhouse to house over many years. If suchobjects can be identified, have been our inopen display, and can be dated fairly pre­cisely (e.g., a child's baby picture or a wed­ding picrure), then the glass can provide anintegrated measure of its exposure to radondaughters. Although appropriate glassobjects are not always available, the feasi­bility of obtaining such measurements onhousehold glass has been demonstrated (l!)in the field in the context of a case-eontrolstudy.

The short-lived radon daughters shownin Figure 1 are electrically charged andavidly form attachments to panicles in theair and surfaces in the room. The attach­ment of these daughters to the room sur­faces is called "deposition" or "plate-out."Once an a-emitting radionuclide, such as2IBpo or 2I4Bi, has attached to the surfaceof a piece of glass in the room, the subse­quent a decay produces an energeticenough "recoil" that (depending on thedirection of emission of the a particle) thedaughter product can become embedded a

short distance into the surface of the glass.The embedding is shallow, but deepenough to resist removal by usual cleaningmethods (.9).

Within a few weeks, virtually all theradon in a room will have decayed to 210Pb,which has a vety long half-life (22 years),but eventually decays to form (after a shonincarnation as 210Bi) 2lOpo. A fraction ofthis 210po will have found its way, via plate­out followed by a-recoil embedding, intothe surface of the glass. One can, in princi­ple then, measure the a panicles emitted bythe embedded 210po, as a dosimetric markerfor long-term radon daughter exposure.The presumption, for use of this technologyin epidemiologic studies, is that the expo­sure of the glass can serve as a fairly goodsurrogate for the residential exposure of thestudy panicipant.

Figure 2 shows the fraction of radonthat persists as 210po after varying lengths oftime. This fraction was computed by apply­ing exponential decay ro the successivedaughters in the decay chain shown inFigure 1, using the known half-lives foreach species (see Appendix). If we make thesimplilYing assumption that the environ­mental conditions, including the patterns ofventilation and air turbulence, haveremained approximately constant over theyears, then this curve can be thought of asrevealing the effective weighting functionfor the implicit integral over time capturedby the measurement of 21Opo that remainsembedded in the glass at time O. Because ofthe long half-life of 210Pb, the embedded210po yields an integrated measure thateffectively averages across decades, presum­ably reflecting exposures during the tenureof the glass in former residences as well as inthe current residence. In this way, a piece ofglass that was not previously owned and hasbeen displayed by the study participant for30 years can provide an integrated exposuremeasure over the decades of its ownership.

The empirical correspondence betweenthe results of a-decay measurements basedon household glass and measurements usinglong-term radon track-etch detectors has

Address correspondence to c.R. Weinberg, NIEHS,PO Box 12233, Research Triangle Park, NC 27709USA.Glinda Cooper, Dale Sandler, and Allen Wilcoxprovided useful comments.Received 9 February 1995; accepted 3 August 1995.

1042 Volume 103. Number 11. November 1995 • Environmental Health Perspectives

Articles· Glass-based radon dosimetry

Tima(years)

Figure 2. The fraction of radon daughter activity from that present at time tyears remaining at time t; 0 inthe form of lIOpO. For example, of the activity present in the room 20 years ago, almost 1% remains in thepresent time in the form of ZIOPO.

Figure 1. The predominant pathways in the decay of 122Rn (radon) down to its stable descendent, 206Pb.The vertical arrows correspond to (l decays, which decrease the atomic weight by four, while the hori­zontal arrows correspond to Bdecays. The half-lives for each species are shown. The airborne carcino­genic descendents are shown by gray shading. Note that there are two points in the sequence whereembedding via recoil into household glass can lead to embedded lIOpO: the decay of lI·PO already adher­ing to the glass to form "'Pb and the decay of z"Po already adhering to the glass to form ZIOPb.

been reasonably good (8-10). Methodsrecently developed now allow the measure­ment to be made wirhout removing theglass from the home (8). The glass iscleaned, and a 2-inch square of CR-39plastic is affixed to its surface and left inplace for a few weeks. Next the plastic isremoved. placed in a sealed bag. andmailed to the investigators, who count thealpha-tracks that have been etched into itssurface by the ongoing random decay of2lOpo residing within the glass.

Although cigarette smoke containsradioactive "1lOpo, this will not be embed­ded into the glass because the parentradionuclide is not in the smoke, and thesmoke-based 210pO therefore has no decaymechanism to cause it to embed in glass.Traces of this 210pO that may remain in afilm on the glass will be removed by clean­ing. and this soutce is thought to con­tribute only neglibly to the measured aactivity (J1).

Plate-out

A key step in this process is the requiredinitial attachment of the daughter radionu­elides to the surface of the glass. Not all theradon daughters in a room plate-out. Manyof these atoms remain airborne and areeventually vented out of the toom as aircirculates. The rate of plate-out depends onthe aetosol content of the room air (J2,13).If there are a lot of panicles in the air, theradon daughters will tend to attach to thematerial in the air rather than to the sur­faces, increasing the likelihood that theywill ultimately be vented out of the roomrather than attach to a surface.

An interesting set of experiments peru­nent to this issue was conducted byBergman and colleagues a decade ago (J4).They took frequent (lOthr) measurementsof the a radioactivity in the air of a roomover 17 hr, beginning when the room ven­tilation system had just cycled of[ After thelevels had stabilized. they lit 12 cigarettesand let them burn passively in the room,giving offside-stream smoke into the ambi­ent air. The results of one such seties ofexperiments are shown in Figure 3. Thefigure shows rhe mean and high and lowexrremes of radioacrivity for five controlexperiments with no cigarette smoke andcorresponding results for studies with ciga­rerre smoke. The levels of airborne radioac­rivity increase in the presence ofsmoke andremain elevared for hours. While there is,as nored above, some 2lOpo radioactivity incigarene smoke. a companion study (J4)carried our in a room thar had low ambientlevels of radon showed thar the radioacrivi­ty inrroduced directly into the air by thesmoke could account for vety little of the

·s·10-15·zo

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1043

Articles' Weinberg

Hours

Figure 3. Data from Bergman et al.!l4} showing the effect of cigarette smoke on the levels of airborne aradioactivity. Details given in text.!Reprinted with permission.}

Figure 4. Schematic showing possible calibrationcurves relating the actual cumulative radon expo­sure to the glass-based result. leading to mea­surement confounding. An incremental change inthe radon exposure has less effect on the glass ina smoky environment than in anonsmoky environ­ment. resulting in a steeper slope for smokyhomes.

tion. Betgman et al. (J 4) proposed thatthe phenomenon they described could bethe basis for the observed excess cancer riskassociated with second-hand smoke, ratherthan a direct carcinogenic effect of thediluted smoke itself. In short, the presenceof smoke may serve to make radon daugh­ters more [or possibly less (J7)] available tothe lung, an effect that can be thought of asdose modification. These are clearly impot­tant questions, but beyond the scope ofthis paper. .

Distinct Calibration CurvesFigure 4 shows the hypothesized relation­ships between 2IOpo activity in glass andthe mean exposure of the glass to radon.An incremental change in the exposure(radon) has a diffetent effect on the glass ina smoky room than in a room with cleanerait. This can be thought of as differentialcalibtation curves, where the proper curverelating the measurement to the exposuredepends on the presence or absence of arisk factor for lung cancer, here cigarettesmoke. Notice that this is not really a mea­surement error problem in the usual epi­demiologic sense: both calibration curvescan be considered "correct" and the prob­lem remains.

What are the consequences of ignoringthis difference in calibration curves andsimply treating the 2IOpo activity in theglass as a sutrogate for long-term radonexposure? Clearly, if smoking is ignoted,radon could spuriously appear to be protec­tive, since smoky houses, where the lungcancer risk is elevated, will tend to showlower radon levels.

As a simple example, suppose the aver­age plate-out is reduced by a fuctor of 0.75in homes of smokers. [This is consistent,for example, with the data shown byMahaffey et al. (submitted), although theyonly had sufficient data to compare houseswith light and moderate smokers.] For sim­plicity, also suppose that smoking status isunrelated to true tadon levels, and radon isuntelated to risk of lung cancer. If we con­sider the situation where each participanthas lived in only one house and assumethat 95% of cases and 35% of controls aresmokers, then one can show [assuming thelognormal distribution of radon levels esti­mated by Nero (I8)1that the unadjustedrelative risk associated with the highestquintile of radon, relative to the aggregateof lower exposures, is 0.75. This spuriouslyindicates a strong proteclive effect.

More realistically, if smoking is "adjust­ed for" but the adjustment is incomplete,in other words, important smoking effectspersist within each crudely defined smok­ing strarum), then the estimated effect of

10

shown to markedly reduce both the levelsof airborne radon daughters and the esti­mated a-radiation dose to the lung (J6).

The data of Mahaffey et al. (submitted)lend futther support to the possibility thatthe fraction of the daughters that plate-outis reduced in a smoky environment. In acase-eontrol study of Missouri women whowere never- or ex-smokers, study subjectswho had both long-term radon detector­based and glass-based measurements werecategorized crudely according to theirsmoking habits after age 18 or according tothe smoking habits of co-residents. Onlythe categories "light" and "moderate" con­tained enough subjects for comparativeanalysis. The incremental change in the 0.

activity in the glass per unit change in themeasured radon exposure was found to beless in homes with moderate smoking thanin homes with light smoking. This is justwhat would be predicted from theBergman data. Again, we see evidence thatsmoky environments retard the plate-out ofradon daughters and reduce the amount of2IOpo embedded in the glass surfaces.Presumably, the same sort of distortionswould occur with other types of air pollu­tion as well, such as those typically presentin smoggy city air.

The existence of such a phenomenonraises important biological questions aboutpossible modification of the radon dose bysmoke. The smoke could serve to increasethe biologically effective radioactive dose tothe lung by increasing the time a-emittingdaughters remain airborne, although theactual effect of particulates on lung doseremains controversial and depends in com­plex ways on the distribution of particlesizes, which affects the "unattached" frac-

Smoky houses

Glass measure

- No cigarette, five experiments

- 12 cigarettes burnt at time 0,fiveeKperiments

300

200

500

400

==...l!...!!

effect. Overall, these data suggest thatsmoke can serve as a carrier for raclon­daughter radioactivity, and this effect canpersist ovet many hours. To the extent thatsmoke can in this way reduce the rate ofplate-out of radon daughters, the daughtersare more likely ro be vented out of theroom rathet than to attach to the surfucesof the room. This suggests that a givenlevel of radon will contribute less embed­ded 210po ro the glass of a smoky roomthan ro the glass of a similat room withcleaner air.

The kind of phenomenon shown inFigure 3 ha~ been recognized by laboratotyresearchers, who sometimes use tobaccosmoke as an aerosol vector to enhancedelivety of radon daughters to the lungs ofexperimental animals (J5). In homes, theuse of an air filtering device has been

1044 Volume 103. Number 11. November 1995 • Environmental Health Perspectives

radon will still be distorted toward showingno risk and may give evidence for protec­tion, by the same kind of bias.

There is also a distortion affecting theassessment of combined effects of smokingand radon on lung cancer risk. Supposethere is a true model relating tadon expo­sure to tisk and suppose the true relation­ship is the same among smokers and non­smokers. Regardless of the model, theincremental effect of a unit change in theglass measure will appear to be greateramong smokers than among nonsmokers.Fundamentally this occurs because a unitchange in smoky houses has a differentmeaning from the same unit change inhouses with cleaner air. Fining a noncon­tinuous model based on categorizing theexposure does not avoid the problem andwill be prone to the same biases.

Choice of Exposure Method forField StudiesRecent case-control studies have relied onlong-term a-track etch detectors (.~5),usually left in place for a year to get anintegrated measure over the seasons. Sincethis kind of device measures filtered radon,rather than the airborne daughters, themeasurement should not be affecred by thepresence of smoke. So we can assume thatthe studies that have already been done arenot subject to systematic biases in radonmeasurement related to smokiness.

On the other hand, problems of inter­pretation arise, even with track-etch mea­surements. Radon is not the active agent ofinterest: the exposure of interest is theshort-lived daughters that irradiate thelung, radon itself being inert with a fairlylong half-life. To the extent that the pres­ence of smoke particles may decrease orincrease the effective integrated dose to therespiratory tract, the traditional measure­ments based on radon gas may overesrj·mate or underestimate the dose to the lungin smoky houses.

On the other hand, the traditionalapproaches do provide a robust measure ofradon, and by including separate dosimetryfor each former house, have the advantagethat risk models can be fitted that allow foreffects of time since exposure, provided onestudies a residentially mobile population.By contrast, the glass-based approach isconstrained by the historical weightingimplied by Figure 2. Moreover, themethod is subject to potential bias due tothe presence ofcigarette smoke.

Future of Glass-based TechnologyThe actual magnitude of the effect ofsmoke on glass-based measurement is diffi­cult to predict on theoretical grounds, and

the bias described could be small enough tobe overlooked in field studies of radon andlung cancer.

However, before retrospective assess­ment based on household glass can be usedwith confidence, more methodologic workis required. Health physicists need to carryout laboratory studies, measuring the plate­out of radon daughters onto glass, usingcontrolled exposure chambers that candeliver a known amount of radon andsmoke. More methodologic field studies ofhousehold glass should also be cartied out.In particular, additional validation studiesneed co be done where measurementsbased on glass are compared with thosebased on radon in air, as measured by long­term track-etch detectors. The resultingregression slopes for smoky and nonsmokyhouses should be compared, as in Figure 4.

Although the distortion of glass-basedexposure assessment by the presence ofsmoke may ultimately lead to the conclu­sion that such methods should not be usedfor case-eontrol studies of radon and lungcancer, the methods may ultimately bewidely applicable for screening. CurrentEPA recommendations call for a short-termscreening test to be done in the lowest liv­ing area of the house; if the result indicatesa potential problem, a longer-term device isplaced to get a more accurate measure­ment. At least several months of measur­ment are required to reduce errors due to

day-to-day variations in radon levels. Usinghouse-specific glass, such as the pane of abuilt~in cabinet or window in a house ofknown age, such a measurement could beaccomplished with greater accuracy (9) andwithin a few weeks. Lively and Steck (9)also point out that the technique "has anadvantage in that the embedded activiry istamper-proof." If screening is the goal, onewould want to identifY houses with poten­tiallevels exceeding some cut~off) currentlyestablished at 4 pCill by the EPA for theUnited States. For houies that are at least afew years old, one could use glass and a cal­ibration curve appropriate to a smoky envi­ronment (the steeper line in Figure 4) toestablish a conservative cut-point based onthe a activity of appropriate windowpanes. Only houses that minimally exceedthis cut-point would then require a follow­up long-term assessment.

In this way, most homeowners andbuyers could be reassured fairly quicklythat the house will not expose their familiesto excessive levels of radon. On the otherhand, for houses with strong evidence ofexcess based on the glass measurements,remediation could be started right away.With this strategy, the houses with trulyhigh levels could be targeted more effi-

Articles· Glass-based radon dosimetry

ciendy than under the current approaches.To accomplish this goal, the glass-basedtechnology will, however, need to be devel­oped further, validated, and made widelyavailable.

Appendix

Calculation of the Curve Shown inFigure 2

The curve of Figure 2 shows rhe appropri­ate weighting function that determines thea activiry in the glass due to its exposure atvarious times, following the simplifYingassumption that the conditions of exposureof the glass (ventilation rates, temperature,air turbulence, etc.) have remained approx­imately constant over the lifetime of theglass. The exposure may not have remainedconstant, as, for example, when the piece ofglass has been carried from house to houseas the study subject changed residences.

Since radioactive decay is exponential,the curve is derived as a simple integral, asfollows. Suppose we follow the fate of anincremental exposure due to the radon thatwas present in a room t years ago. Theintermediate daughters with very shorthalf-lives can be neglected, because virtual­ly all of that radon will have decayed to

21°Pb within a few weeks. The fraction ofthese lead atoms that persisrs in the form of21Opo can be calculared as an integral. Ifthe 210Pb decays according to C[exp(-t A)]and 21Opo decays according to C[exp(-t/)],then we know that A is In(2)/22 and /) isIn(2)/(138/365), if t is expressed in years.This follows from the knowledge of theirrespective half-lives as 22 years and 138days. The events leading to 21Opo involvedecay of 210Pb at time s followed by the sur­vival of 210pO for time lasting at least t- s.Then we simply need to integrate over allchoices of sfrom 0 to t, as follows:

1t , -,<, -Olt-,}ds A [-At -Ot]fl.e e =---e-eo (8-A)

This corresponds to the curve displayed inFigure 2. If a piece of glass has had a time­varying exposure, as in typical scenarioswhere people move from house to house,then the resulting activiry in the glass shouldbe approximately proportional to the inte­gral of the product of the curve showing thetrue radon levels multiplied by the curve ofFigure 2. The proportionality constantdepends on the plate-out rate for radondaughters and the ventilation tates for therooms in which the glass was exposed.

Of course, if the glass has been exposedin several different residences over its life-

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1045

Articles' Weinberg

time, the tesidual embedded a. activitydetermined by the exposures and subse­quent decays cannot distinguish betweenhigh exposures that happened long ago andmoderate exposures of recent origin. Thuswith this method of measurement, theintegration described cannot be decon­volved, and consequently one cannot fitrisk models that take into account effects oftime since exposure.

REFERENCFS

1. Commine< on .he Biological Effects ofIonizing Radiations IV. Heal.h risks of radonand other internally deposited alpha·emincrs.Washington. DC:National Academy Press,1988.

2. Lubin JH, Liang Z, Hrubec Z, Penhagen G,Schoenberg JB, Blot Wj, Klotz JB, Xu Z-Y,Boice: JD. Radon exposure in residences andlung cancer among women: combined analysisof three studies. Cancer Causes Control5:114-128 (1994).

3. Letourneau EG, Krewski D, Choi NW,Goddard MJ, McGregor RG, Zielinski JM, DuJ. Case·comrol study of residential radon andlung cancer in Winnipeg, Manitoba, Canada.AmJ EpidemioI140:3W-322 (1994).

4. Pershagen G, Aketblom G, Axelson 0,Clavensjo B, Damber L, Desai, G, Enflo A,Lagarde F, Mellander H, Svartengren M,Swedjemark GA. Residemial radon exposureand lung cancer in Sweden. N Engl J Med330:159-164 (I994).

5. Alavanja MCR, Brownson RC, Lubin JH,Berger E, Chang J, Boice JD. Residential radonexposure lung cancer among nonsmokingwomen. J Nat! Cancer Inst 86:1829-1837(1994).

6. Lively RS, Ney EP. Surface radioactivity result­ing from the deposition of Rn-222 daughterproducts. Health Phys 52:411-415 (I987).

7. Samuelsson C. Retrospective determination ofradon in houses. Natute 334:338-340 {I 988).

8. Mahaffey JA, Parkhurst MA, James AC, CrossFT, Alavanja MCR, Boice JD, Ezrine S,Henderson P, Brownson RC. Estimating pastexposure to indoor radon from household glass.Health Phys 64:381-391 (1993).

9. Lively RS, Steck DJ. Long-term radon concen­trations estimated from Po-210 embedded inglass. Health Phys 64:485-490 (1993).

10. Samuelsson C, Johansson L, Wolff M. Po-210as a tracer for radon in dwellings. Radiat ProtDos 45:73-75 (1992).

II. Comelis J, Landsheere C, Ttier AV,Vanmarcke H, Poffijn A. Experiments on glass·absotbed polonium-210. Appi Radiat Isot43:127-138 (1992).

12. Bigu J. Effect of selected variables on aitborneRn-220 progeny concentrations. Health Phys54:93-98 (1988).

13. Knutson EO. Modeling indoor concentrationsof radon's decay products. In: Radon and itsdecay producu in indoor air, New York(Nazaroff WW, Nero AV Jr, eds). NewYork:John Wiley and Sons, 1988;161-202.

14. Bergman H, Edling C, Axelson O. Indootradon daughter concentrations and passivesmoking. Environ 1m 12:17-19 (1986).

15. Johnson NF, Newron GJ. Estimation of thedose of radon progeny to the peripheral lungand the effect of exposure ro radon progeny onthe alveolar macrophage. Radiat Res139:163-169 (1994).

16. Hopke PK, Jensen B, Momassier N. Evaluationof several air cleaners for reducing indoor radonptogeny. J Aer Sci 25:395-405 (1994).

17. Wasiolek PT, Hopke PK, James AC.Assessment of exposure to radon decay prod­UCtS in realistic living conditions. JExpo AnalEnviron Epidemiol 2:309-322 (1992).

18. Nero A, Schwehr M, Nazaroff W, Revzan K.Distribution of airborne radon-222 concentra­rions in U.S. homes. Science 234:992-997(1986).

The San Francisco office of the Natural Resources Defense Council, a national nonprofit

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People of color are encouraged to apply.

1046 Volume 103, Number II, November 1995 • Environmental Health Perspectives

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Meeting~_ort _

Role of Chelating Agents for Prevention, Intervention, and Treatment ofExposures to Toxic MetalsR.A. Goyer, l M.G. Cherian/ M.M. Jones,3 and J.R. Reigart4

'National Institute of Environmental Health Sciences. Research Triangle Park. NC 27709 USA; "University of Western Ontario. LondonN6A5Cl Canada; 3Vanderbilt University, Nashville, TN 37235 USA; 'Medical University of South Carolina, Charleston, SC 29425 USA

The role of chelating agents fat the pteven­tion, intervention, and treatment of expo­sures lO roxic metals was (he topic of a con­fetence held at the National Institute ofEnvironmental Health Sciences, 22-23September 1994. The objective of the con­ference was to review experimental andclinical studies concerned with the effective­ness and potential toxicity of chelatingagents used to reduce the body burden ofvarious metals and to identify reseatchneeds in the area of chelation. The confet­ence was prompted by emerging evidencethat low-level exposures to metals mayresult in roxic effects nor previously recog­nized. For example, the recent interest inuse of chelation as an intervemion strategyto reduce blood lead levels followed theawareness that exposure to lead in infantsand young children resulting in blood leadlevels as low as 10-15 pg/dl may impaircognitive and behavioral development (I).The question increasingly asked is to whatdegtee, if any, does increased excretion of atoxic metal reverse established toxicity? Forexample, does reduction in blood lead levelsreverse the impairment of cognitive andbehavioral development in children? Doesthe process of chelation cause potentiallydangerous redistribution of lead to suscepti­ble organs from those less susceptible tolead toxicity? While intervention for toxici­ty from any metal includes removal fromexposure. what are the indicarions for usingchelating agents that enhance excretion ofmetals?

Complete answers to these questionsmay not be currendy available, but discus­sion of benefits and problems related tochelation therapy should help identifY areasneeding furrher study. The conference par­ticipants were asked to share current dataand to identify gaps in data necessary [Q

obtain a bener understanding of the properplace of chelating agents in the manage­ment of metals exposure and toxicity.

Chelation of Lead with EDTAIt was suggested at the conference that theessential characteristics of an ideal leadchelator are I) rhe ability to reduce the cel­lular lead burden in the target cells for leadtoxicity, 2) the ability to restore or preventlead-induced loss of cell function, 3) theabsence of adverse effects produced by

interfering with homeostasis and uriliza­tion of essential trace elements, and 4) noor little intrinsic toxicity (~.

Historically, the drug of choice intreatment oflead toxicity is EDTA (disodi­urn ethylenetetraacetate) (J,3). The com­mon practice of treating children with highlead exposure (blood lead levels of 70-100pg/dl) wirh a combination of EDTA andBAL (British anti-Lewisite, Dimetcaprol) isbelieved to reduce mortality from leadencephalopathy from about 30% to 1 or2% and is more effective under these cir­cumstances than treatment with EDTAalone. EDTA may not be approptiate fattreating low-level lead exposures because itmust be given parenterally, and it can betoxic in that it increases excretion of someessential metals. EDTA produces substan­tial diuresis of zinc and a temporary30-40% decrease in plasma zinc (4).

The relationship between blood leadconcenuation and the quantity of leadexcreted with EDTA treatment is nonlin­eat. Arithmetic increases in blood lead ateassociated with exponencial increases inexcretion of lead. As blood lead levelsdectease, the risk-benefit ratio for EDTAbecomes progressively less favorable. Thelead-chelate complex is filtered by the renalglomerulus with a biological half-time of1.5 hr. In subjects with normal renal func­tion most of the lead--<:helate complex isexcreted within 8 hr, bur excretion maytake as long as 3 days in persons with renalfailure. In children in which exposure tolead is of relatively shorr duration, the cor­telation between blood lead and chelatablelead is variable. In adults with temote pastexposure, the couelation between bloodlead and chelatable lead is poor. A latgetfraction of the lead burden in childrenresides in soft tissues compated to adults.After a single challenge dose of EDTA,lead is excreted largely from blood and softtissues (5-7). Howevet, a single EDTAueatment does nor ptoduce a dtamaticdectease in bone lead as measured by L x­ray fluotescence (L-XRF) in children (8,9).K-XRF measurements of bone lead aresuperiot to chelation challenge tests as amarker of long-term lead exposure (5). Inadults, bone lead measured by trans-iliacbiopsies or by in vivo tibial K-XRF corre­lates well with chelarable lead duting long-

term chelation therapy. The upper limit ofnormal lead-chelate excretion is about 650pglday for adults and is comparable to thatreporred in children when notmalized forbody mass. In adults with elevated bonelead from chronic lead poisoning, there isdecrease in blood, bone, and chelatable leadduring long-term chelation. Reequilibrationbetween blood and bone lead takes about 2weeks (7,10.

EDTA nephrotoxicity as described inearliet literature is not found with the cur­tendy available pyrogen-ftee calcium salt attecommended dosage «50 mg/kg) (ll).Experimental studies of efficacy of EDTAand dimercaptosuccinic acid (DMSA) sug­gest that the toxicokinetics of lead diffet inolder animals, and there is less reduction inliver and kidney lead than in younger rats.Excretion of essential trace metals afterchelation therapy with EDTA or DMSA isgreatet in older animals than in youngeranimals (J~.

Chelation of Lead with DMSAThe Food and Drug Administration hasrecently licensed the drug DMSA (suc­cimer) for reduction of blood lead levels~45 pg/d1. This decision was based on thedemonstrated ability of DMSA to reduceblood lead levels. An advantage of this drugis that it can be given orally. However,there is no information tegarding ilS effec­tiveness in reversing the clinical effects oflow-level lead exposure, including effeclS onthe central nervous system. Interest in usingDMSA to treat low-level lead exposute hasprompted studies tegarding the source ofthe endogenous lead temoved by this drug,its possible redistribution between organs,and whether DMSA increases gastrointesti­nal absotption of lead, since it is adminis­tered orally. Answets to these questions areincomplete. While studies in animals showthat DMSA does not seem to redistributelead into the btain from other organs, thereis no consensus as to the effectiveness ofDMSA in removal of lead from brainand/or bone (J3). One study using stableisotopes of lead suggests that DMSA mayenhance gastrointestinal absorption of lead,

Address correspondence (0 R.A. Goyer. NIEHS.PO Box 12233. R=rch Triangle Park, NC 2n09USA.

1048 Volume 103, Number II, November 1995. Environmental Health Perspectives

but this may be telated to dose, duration oftreatment and, of course, the amount oflead in the gut (I4).

Results of a clinical trial were presentedin which rhe effectiveness of DMSA inremoval of lead from ·19 children withblood lead levels of 5Q-{)9 flg/dl was com­pared to treatment of 4 comparable chil­dren with EDTA. DMSA decreased bloodlead by 61 %, whereas in 4 children treatedwith EDTA, blood lead decreased by 45%.The group of 4 children receiving EDTAwas too small to evaluate for statistical sig­nificance. However, urinary lead was com­parable in the two groups. There is a posi­tive correlation between blood lead levelsand half-time elimination of DMSA, sug­gesting that lead may interfere with renalexcretion of DMSA and possibly otherdrugs. Concomitant anribiotics mightslightly decrease the efficacy of DMSA (I5J.

Most of the DMSA excreted in theurine of humans is in the form of a mixeddisulfide in which each of the sulfur atomsof DMSA is in disulfide linkage with a cys­teine molecule. There is a small amount ofexcreted DMSA in which only one mole­cule of cysteine is in disulfide linkage withDMSA. In an experimental study it wasfound that synthetic DMSA:cysteine (I :2)mixed disulfide mobilizes and increases theexcretion oflead in rats preloaded with leadacetate (I6).

The actions of DMSA and EDTA oncellular metabolism of lead have been com­pared in cultures of osreoclastic bone cells.Both DMSA and EDTA have distinct andcomplex effecrs on the cellular metabolismof lead. Both compounds reduce the size ofthe largest and most stable subcellular poolof lead. However, EDTA increases the sizeof the most rapidly exchanging Pb2+ poolwithout effecting a significant reduction inthe total cellular burden. In contrast,DMSA only slightly increases the interme­diare lead pool, but effectively reduces thetotal cellular lead burden. These experi­ments indicate that DMSA alters the trans­fer of lead within cells such that a greaterpercentage of total cellular lead present incells is in a readily exchangeable pool.Neither DMSA nor EDTA is particularlyeffective in restoring lead-impaired cellfunctions such as protein synthesis, por­phyrin synthesis, heme synthesis, andosteocalcin expression, even though cellularlevels oflead are diminished (2).

Experimental studies in animals haveshown that, because of differences in thetoxicokinetics of lead in animals at differ­ent ages, older (mature) animals mayrequire larger doses of chelating agent thanyounger animals to remove a particularamount of lead. Also, EDTA increases

excretion of essential metals, calcium, andzinc, whereas DMSA increases the excre­tion of copper. Human studies have alsoshown that excretion of copper, and to alesser degree zinc, are increased by DMSAadministration (4,12,17,18).

Chelation of Lead withD-PenicillaminePenicillamine has been used ro chelatetoxic metals including copper (in Wilson'sdisease) as well as lead, mercury, andarsenic. It has been approved by the FDAfor treatment of Wilson's disease, cysti­nosis, and rheumatoid arthritis but not forlead poisoning, primarily to avoid its mis­use in the workplace. Nevertheless, a sub­stantial body of experimental and clinicaldata exists regarding the pharmacology andutiliry of penicillamine in both adult andchildhood lead poisoning. Experience atthe Lead Clinic of the Boston Children'sHospital suggests that D-penicillamineincreases excretion of lead with a minimalrisk to children with blood lead levels <35flg/dl. Penicillamine may produce substan­tial reduction in blood lead levels and lessrebound rhan rrearment with DMSA orEDTA probably due to the continuiry ofthe penicillamine treatment. Potential sideeffects include hypersensitivity reactions,particularly in subjects allergic to penicillin(I9J.

Effects of Lowering Blood Lead byChelationNIEHS is sponsoring a randomized, multi­center clinical trial of about 1300 childrenunder 24 months of age is currently testingthe effectiveness of succimer in reversingthe slower cognitive and behavioral devel­opment in children with blood lead levelsbetween 20 and 44 flg/dl. The trial will beconducted on a double-blind basis, and fol­low-up of the children will extend for atleast 2 years. Other interventions such ashome cleanup and nutritional supplemen­tation will be done for all children. Resultswill not be available for some time (20).

A preliminary study presented at theconference showed that lowering blood leadlevels in children does not result in a signifi­cant beneficial effect on growth (length orheight). However, the study did not involvea control group and did not assess dietaryand socioeconomic factors (21).

Chelation of MercuryAnother objective of the conference was toreview the effectiveness of drugs forremoval of mercury. The two chelatingagents that have been most studied forremoval of mercury are DMSA and a relat­ed drug, 2,3-dimercapto-I-propanesulfonic

Meeting Report· Chefating agents

acid, (DMPS, dimaval) (22). DMSA andDMPS are chemical analogs of BAL(dimercaprol) and can be administeredorally. However, the two drugs are bio­transformed differently in humans. Morethan 90% of DMSA excreted in urine ofhumans is in the form of a mixed disulfidein which each of the sulfur atoms ofDMSA is in disulfide linkage with a cys­teine molecule. After DMPS administra­tion, however, acyclic and cyclic disulfidesof DMPS are the major metabolites in theurine (23,24). Both DMSA and DMPSincrease the urinary excretion of mercury.

Animal studies have shown that DMPSexhibits some organ specificiry in the chela­tion of mercury (25,26). In rats exposed tomercuric chloride or mercury vapor,administration of DMPS increased urinaryexcretion of mercury and decreased renalmercury content. The inctease in urinaryexcretion was directly proportional to therenal burden of mercury in rats injectedwith mercuric chloride or exposed to mer­cury vapor. Thus, DMPS may be of poten­tial use to measure the renal burden ofleadand mercury.

About two-rhirds of the mercuryexcreted in persons with mercury-contain­ing dental amalgams appears to be derivedfrom mercury vapor released earlier fromtheir amalgams, and a highly significantpositive correlation has been foundbetween numbers and sizes of amalgam fill­ings and urinary mercury excretion follow­ing DMPS administration (2,i).

In a clinically controlled trial in whichhalf the subjects received DMSA and theother half received a placebo, DMSAincreased the urinary excretion of lead,copper, mercury, and, to a lesser degree,zinc in the first 24 hr; lead excretionincreased about 10-fold over controls,whereas both copper and mercury doubled.Although DMSA enhances excretion ofmercury, lead is the toxic metal most clear­ly affected by DMSA treatment (I,i).

While elemental or inorganic mercurycan be removed from tissues by chelatingagents, it is unlikely that methylmercury canbe chelated (28). The methylmercurycation, CH

3Hg+, forms a thermodynamical­

ly stable bond with the deprotonated thiolgroup. Thus, the formation of only onebond between mercury atom and anotherligand precludes the formation of ring struc­tures needed to produce a metal chelate.However, the strong linear bond formedbetween mercury and a rhiol group allowsthe formation of a variety of complexes,whereby thiol-containing compounds maybe used for antidotal therapy. Exchangewith the protein-bound mercurial should berapid (29), provided that the thiol com-

Environmental Health Perspectives. Volume 103, Number 11, November 1995 1049

Meeting Report· Goyer et al.

pound to be used as an antidote can pene­trate the macrostructure of proteins to reachthe site of the bound mercury.

Metallothionein, a Natural ChelatorMetallothionein (MT) was discovered in1957 as a cadmium-binding prorein in therenal COrtex of the horse and is character­ized as a low molecular weight (>9000 Da),cysteine-rich, metal-binding protein.Mammalian MT contains 61 amino acids.The protein contains no aromatic aminoacids or histidine. Twenty of the 61 aminoacids are cysteine, and are arranged in ahighly conserved sequence which isobserved in vertebrate, invertebrate, yeast,and plant MT. Metals bind to MT inmetal-thiolate complexes exhibiting tetra­hedral (cadmium, zinc) or trigonal (cop­pet) geometty. Two major isoforms of MT(designated MT I and II) have been identi­fied in most species and are controlled sep­arately by different genes. Humans containsubforms of the two isoforms. Recently, athird isoform (growth inhibitory factor,MT III) has been identified in the brain.The MT molecule is divided into two dis­tinct metal-binding domains. The carboxylterminal half of the molecule is designatedthe a.-domain and represenrs amino acids30-61. It contains 11 cysteinyl residuesand binds four atoms of zinc or cadmiumor six atoms of copper. The IS-domain isthe amino-terminal half of MT and con­tains nine cystinyl residues. This domainbinds three ions of zinc or cadmium or sixcopper ions. MT exhibits numerous bio­logical and physiological functions. Itappears to have a role in zinc and coppermerabolism. The.induction of MT protecrsorganisms from toxic metals such as cadmi­um. MT also exhibirs free-radical scavagingactivity. Medically, the induction ofintesti­nal MT by zinc therapy is correlated withnormal to negative copper balance in

patients with Wilson's disease. Renal MTinduction also protecrs the intestine againstthe toxic effects of cisplatin treatment.However, tumor cells that are resistant toelecrrophilic antineoplasric agents exhibitincreased cellular MT levels. Thus, MTmay protect some tumor cell types againstthe effecrs ofcertain antitumor drugs (30).

The toxicity of the cadmium-metal­lothionein complex precludes any consider­ation of use of this natural metal-ligand forclinical use to enhance excretion of metals.

Chelation of CadmiumDeveloping an effecrive chelation therapyfor cadmium is difficult because cadmium istightly bound to metallothionein in liverand kidney. Cadmium in liver has a longhalf-life (about 30 years in humans) and isgradually mobilized from liver to kidney,which is considered the critical organ forcadmium toxicity. The cadmium-metal­lothionein complex is extremely toxic to thekidney (31), and most chelating agents thatdo remove cadmium from the liver areexcreted by the kidney, producing nephro­toxicity. Therefore, the best approach tochelating cadmium from the liver is throughbile, before it reaches the kidney. A numberof substituted dithiocarbamate compoundswith a pair of sulfur atoms that serve asdonors to cadmium are the most promisingtypes ofchelating agenrs for cadmium mobi­lization. Sodium N-(4-methoxybenzyl)-o­glucarnine dithiocarbamate (MeOBGDTC)is one of the most effective for removingcadmium from liver and kidney. Cadmiumis then excreted in bile complexed withMeOBGDTC and glutathione (32,33).Although MeOBGDTC and other similarcompounds have been shown to be effectivein removing cadmium from tissues of exper­imental animals with cadmium exposure,efficacy in humans has not been demon­strated.

Conference Presenters

Selective Removal of Copper Boundto Metallothionein byTetrathiomolybdate

The affinity of copper for binding to MT ishigher than that of zinc or cadmium.However, it has been recently shown thatcopper can be removed both in vitro and invivo by tetrathiomolybdate (TIM) withoutaffecting the other two metals bound toMT. The mechanisms whereby TTMremoves copper have been studied in a ratmodel for Wilson's disease, the LEC rat,which expresses a genetically defective cop­per-dependent ATPase thar regulares cop­per emux (34).

TIM appears to remove copper fromMT and facilitates excretion by three dif­ferent reaction pathways. When rheamount ofTIM (from tepeated injections)is less than half the amount of copperbound to MT, TIM appears to removecopper only from cytosolic MT; Zn-MTand apo-MT remain in the cytosol(Cu,Zn-MT ~ Cu,Zn-MT/TIM ~ Zn­MT/apo-MT). Copper remaining in theliver is present as a copper-molybdenate­sulfur polymer. A putarive dimer,MT-TIM connected by a (TIM)-S-Cu­S-(MT) bridge, is also formed. WhenTIM is grearer than half the amount ofcopper, the TIM dissociates copper fromthe MT- TIM complex and copper for­merly bound to MT becomes associatedwith a high molecular weight protein in rhecytosol. The copper-molybdenare complexbound to the high molecular weight pro­tein is assumed to be a soluble oligomercomplex and is thought to be excretedfrom the liver. A rhird pathway for removalof copper from MT by TIM is by facilitat­ing the polymerization of rhe soluble (Cu­S-MoSz-S-) polymer to an insoluble (-Cu­S-MoSz-S) polymer (35).

H. Vasken Aposhian, University of ArizonaM. George Cherian, University of Western OntarioJulian Chisolm, Johns Hopkins UniversityThomas Clarkson, University of RochesterDeborah Coty-Slechta, University of RochesterPatricia Durbin, University of California-

Lawrence Berkeley LaboratotyJames FoulS, National Institute of Environmental

Health SciencesArthur Gtidet, University ofTexas at AustinRobert Goyer, National Institute of Environmental

Health SciencesJohn Graef, Boston Children's HospitalPhilippe Gtandjean, University of Odenese, Denmark

1050

Joseph Graziano, Columbia UniversityMark Jones, Vanderbilt UniversityMichael J. Kosnett, University of California at San FranciscoRichard Maiorino, University of ArizonaMaty Ellen Mortensen, Children's Hospital, Columbus, OhioJanet Phoenix, National Safety CouncilJoel Pounds, Wayne State UniversityKen N. Raymond, University of California at BerkeleyWalter Rogan, National Institute of Environmental

Health SciencesJohn Rosen, Montifiore HospitalDon Smith, University of California at Santa CruzK.T. Suzuki, Chiba UniversityRichard Wedeen, Medical and Dental College of New Jersey

Volume 103, Number 11, November 1995 • Environmental Health Perspectives

Design of New Chelating Agents forRemoval of Cadmium, Copper, andActinides

For the design and development of newchelaring agenes for reducing body burdenof metals such as cadmium, copper, andthe radioactive actinide elemenes, Pu(JV),NpM, and UM), specific chemical, phys­iological, and pharmacological propertiesmust be included in the molecule (36.37).There are various approaches ro achievingthe appropriate design. One approach is roidentify an indicaror compound by selec­tive screening of possible candidates.Another approach is ro start by ideneifyingthe possible ways in which a chelatingagent strucrute can be designed to matchthe geometric and chemical preferences ofthe ceneral (toxic) metal ion under consid­eration. This method is illustrated by thedevelopmene of chelating agents to mobi­lize cadmium from its intracellular deposit(38). Compounds in this category includedithiocarbamates, mono- and diesters ofmeso-2J-dimercaprosuccinic acid.

The design of an improved chelatingagene for lead has involved an examinationof a series of bidentate ligand functionalitiesthat show some significane affinities or pref­erences for lead (36). This was followed bythe design and synthesis of multidentate lig­ands based on the coordination propeniesof Pb2• found in simple natural systems,particularly the low-molecular weight pep­tides found in plants or other organisms(39). Some of the lead-sequestering agentsidentified by this approach are the thiohy­droamato complexes, and mono- and bis­(hydroxypyridinethione) ligands (40).

ConclusionIn summary, the conference achieved itspurpose of highlighting the current pat­terns of clinical usage of chelating agents aswell as the current status of promisingexperimental drugs. Insights were providedas to how to design new agents.

The conference also brought into focusquestions about the effectiveness of cur­rently available drugs. Although drugs incurrent use are effecrive in lowering levelsof toxic metal in body fluids, there is littleinformation about removal of toxic metalsfor tissues or reversal of toxic effects. Theissues discussed in the conference have pro­vided the basis for identifying the followingresearch needs:

I) Determine the sites from which leadis removed during chelation therapy andidentify which chelator is most effective inremoving lead from the nervous system.

2) Determine if intervention withchelating agents enhances the reversal of

functional impairment of cognitive andbehavioral development associated withexposure to lead.

3) Better characterize essential metalexcretion during intervention with chelat­ing agenes, particularly DMSA.

4) Determine whether orally adminis­tered chelating agenes enhance absorptionof toxic metals from the gastrointestinaltracr.

5) Determine whether there are advan­tages to the simultaneous use of multiplechelating agenes.

6) Perform longer-term experiments onlead-loaded primates ro investigate removalof lead from bone. Such information mightbe useful in devising clinical treatments toremove lead from bone. How do differentintervention regimens with or withoutchelating agents compare in terms ofremoval of lead from tissues particularlythe nervous system and bone' This infor­mation might help avoid later problemswhich arise under circumstances when suchlead is remobilized as a result of pregnancyor disorders of bone metabolism such asosteoporosis.

7) Develop and clinically test chelatingagents for removal of cadmium. Furthertest the use of DMSA and DMPS forremoval of mercury.

8) Assess the use of less common toxicmetals for effective antagonists. Theseinclude thallium, beryllium, and theradioactive actinide metals.

REFERENCES

1. CDC. Preveming lead poisoning in young chil­dren: a statement by the Centers For DiseaseControl. Atianta,GA:Centers for DiseaseControl; 1991.

2. Pounds JG. EffectS of lead on cellular leadmetabolism and toxicity. In: Abstracrs from theconference on the role of chelating agents forthe prevention, intervention, and treatment ofexposures to toxic metals, 22-23 September1994, Research Triangle Park. NCi A3.

3. Piomelli S, Rosen JF, Chisolm JJ Jr, GraefJW.Management of childhood lead poisoning. JPediarr 105:523-532 (984).

4. Chisolm JJ Jr. Indications for treatment of leadtoxicity and CaNa2EDTA. In: Abstracts fromthe conference on the role of chelating agentsfor the prevention, intervention, and treatmentof exposures to toxic metals, 22~23 September1994, Research Triangle Park, NCi A8.

5. Kosnecr MJ, Regan LS, Kelley TJ, Osterloh JD.Interrelationships of urinary lead after DMSAchallenge. bone lead burden and blood lead inlead exposed workers. Vet Hum Toxicol36:363 (994).

6. Cory-Slechta DA, Weiss B, Cox C.Mobilization and redistribution of lead over thecourse of CaEDTA chelation therapy. ]Pharmacol Exp Ther 243:804-813 (987).

7. Batuman V, Wedeen RP, Bogden ], BalestraDJ, Jones K, Schidlovsky G. Reducing bonelead content by chelation treatment in chronic

Meeting Report· Chelating agents

lead poisoning. An in vivo X~ray florescenceand bone biopsy study. Environ Res 48:70-76(1989).

8. Rosen JF, Markowicz ME, Bijur PE, Jenks ST,Wielopolski L, Kalef-Ezra JA, Slatkin DN.Sequential measurements of bone lead contentby X~ray fluorescence in CaN~EDTA-treated

lead-toxic children. Environ Health Perspect91:57-62 (991).

9. Markowicz ME, Bijur PE, Ruff HA, Rosen JF.The effects of CaNa2EDTA chelation in mod­erate childhood lead poisoning. Pediatrics92:265.271(993).

10. Wedeen RP, Batuman V, Quinless F, WilliamsFH Jr, Bogden J, Schidlovsky G, Jones !CW. Invivo x~ray florescence (XRF) for assessing bodylead stores. In: In vivo body composition stud­ies (Ellis K], Yasumua S, Morgen W, eds)London: Institute of Physical Science andMedicine,1987;357-362.

11. Wedeen RP, Batuman V, Landy E. Thesafetyof the EDTA lead-mobilization test. EnvironRes 30:58-62 (1983).

12. Cory-Slechta DA. Lead exposure duringadvanced age: alterations in kinetics and bio­chemical effects. Toxicol Appl Pharmacol104:67-78(990).

13. Jones MM, Basinger MM, Gale GR, AtkinsLM, Smith AB, Stone A. Effect of chelate treat~

ments on kidney, bone and brain lead levels oflead~intoxicated mice. Toxicology 189:91-100(994).

14. Smith DR, Flegal AR. Srable isotopic tracers oflead mobilized by DMSA chelation in low lead­exposed rats. Toxicol Appl Pharmacal 116:85~

91 (992).IS. Graziano JH, LoIacono N, Moulton T.

Controlled study of meso-2,3-dimerc3tosuc­cinic acid (DMSA) for the management ofchildhood lead intoxication.] Pediatr 120:133~

139(1992).16. Maioriano RM, Aposhian MM, Xu ZF, Li Y,

Polt RL. Aposhian HV. Determination andmetabolism of dithiol chelacing agents. XV.The meso-2,3-dimercatposuccinic acid~cysteine

(l :2) mixed disulfide, a urinary metabolite ofDMSA in the human, increases the urinaryexcretion of lead in the rat. J Pharmacol ExpTher 267:1221-1226 (1993).

17. Grandjean P. Eff'ectofchelation treatmenrwithDMSA on [race element status: a clinical con­trolled trial. In: Abstracts from the conferenceon the role of chelating agents for the preven­tion, intervention, and treatment of exposuresto toxic metals, 22~23 September 1994,Research Triangle Park, NCi A19.

18. Cory-Slechta DA. Mobilization of lead over thecourse of DMSA chelation therapy and long.term efficacy. J Pharmacol Exp Ther 246:840­891 (988).

19. Graef J. Penicillamine for treatment of leadtoxicity. In: Abstracts from the conference onthe role of chelating agents for the prevention,intervention, and treatment of exposures totoxic metals, 22-23 September 1994, ResearchTriangle Park, NC; A23.

20. Rogan W. Toxicity of lead in children trial. In:Absrracrs from the conference on the role ofchelating agents for the prevention, interven~

tion, and treatment of exposures to toxic met­als, 22-23 September 1994, Research TrianglePark, NC; A12.

21. Mortensen ME. Impact of chelation on growthof lead poisoned children. In: Abstracts fromthe conference on the role of chelating agents

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Meeting Report· Goyer et al.

for the prevention, intervention. and treatmentof exposures to toxic metals, 22-23 September1994. Research Triangle Park. NC; A12.

22. Aposhian HV. DMSA and DMPS-water solu­ble antidotes for heavy metal poisoning. AnnuRev Pharmacol ToxicoI23:193-215 (1983).

23. Aposhian HV. Aposhian MM. Meso-2.3­dimercaptosuccinic acid: chemical, pharmaco­logical and toxicological propenies of an orallyeffective metal chelating agent. Annu RevPharmacol ToxicoI30:279-306 (1990).

24. Hutlbut KM. Maiotino RM. Mayersohn M.Dart RC. Bruce DC, Aposhian HV.Determination and metabolism of dithiolchelating agents. XVI. Pharmacokinetics of 2,3·dimercato-I-propanesulfonatc after intravenousadministration to human volunceers. JPharmacol Exp Thet 268:662-668 (1994).

25. Twarog T. Cherian MG. Chelation of lead bydimercapcopropane sulfonate and a possiblediagnostic use. Toxicol Appl Pharmacal 72:550-556 (1984).

26. Cherian MG. Miles EF. Clarkson TW. Cox C.Estimation of mercury burdens in rats by chela­tion with dimercapropropane sulfonate. J.Pharmacol Exp Ther 245:479-484 (1988).

27. Aposhian HV. Bruce DC. Alter W. Dan RC,Hurlbut KM, Aposhian MM. Urinary mercuryafter administration of 2.3-dimercaptopropane­I-sulfonic acid: correlation with dental amal­gam score. FASEB j 6:2472-2476 (1992).

28. Clarkson T. Can methyl mercury be chelated?

In: Abstracts from the conference on the role ofchelating agents for the prevention, interven­tion, and treatment of exposures to [oxic met­als. 22-23 September 1994. Research TrianglePark. NC; A12.

29. Kostyniak p. Clarkson T. The role of chelatingagents in metal toxicity. Fundam Appl Toxicol1:376-380 (1981).

30. Grider A. Metallothionein, a natural chelator.In: Abstracts from the conference on the role ofchelating agents for the prevention, interven­tion, and treatment of exposures to toxic met­als, 22-23 September 1994, Research TrianglePark. NC; A12.

31. Chan HM. Zhu L-F, Zhong R, Grant 0,Goyer RA, Cherian MG. Nephrotoxicity in ratsfollowing liver transplanration from cadmium­exposed rats. ToxicoI Appl Phatmacol 123:89­96 (1993).

32. jones MM. Cherian MG. Singh PK. BasingerMA, Jones SG. A comparative study of theinfluence of vicinal dithiols and a dithiocarba­mate on the biliary excretion of cadmium inthe rat. Toxicol Appl PharmacoI 110:241-250(1991).

33. Gale GR. Smith AB, jones MM. Singh PK.Evidence of active transport of cadmium com­plexing dithiocarbamates into renal and hepaticcells in vivo. Phatmacol Toxicol 71:452-456(1992).

34. Suzuki KT, Yamamoto KY. Kanno S. Aoki Y.Takeichi N. Selective removal of copper bound

to metallothionein in the liver of LEC rats bytetrathiomolybdate. Toxicology 83: 149-158(1993).

35. Suzuki KT. Yamamoto KY. Ogra Y. Kanno S.Aoki Y. Mechanisms for removal of copperfrom metallothionein by tetrathiomolybdate. JInorg Biochem 54:157-165 (1994).

36. Raymond KN, Durbin PW, The design. syn­thesis and evaluation ofsequestering agenrs spe­cific for plutonium(IV}. In: Proceedings of thefirst Hanford Separation Science Workshop,23-25 july 1991. PNL-SA-21775. Richland,WA:Bauelle Pacific Northwest Laboratories,1993.

37. Jones MM, Newer chelating agents for in vivotoxic metal mobilization. Comments InorgChern 13:91-110(1992).

38. jones MM. Cherian MG. The search forchelate antagonists for chronic cadmium intoxi­cation. Toxicology 62: 1-25(1 990).

39. Abu-Dari K. Ekkehardt Hahn F, RaymondKN. Lead sequestering agents 1. synthesis,physical properties and structure of lead thiohy­droxarnato complexes. J Am Chern Soc112:1519-1524 (1990).

40. Abu-Dari K. Karpishin TB. Raymond KN.Lead sequestering agents. 2. Synthesis ofmono- and bis-(hydoxypyridinethione) I i g ­ands and their lead complexes. Srrucwre ofbis(6-carbomoyl)-I-hydroxy-2( 1H)-pyridine-2­thionato-(O.S)lead(lI). Inorg Chern 32:3052­3055 (1993).

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:~{~E AMERICAN SOCIETY FOR CELL BIOLOGY

Thirty-Fifth Annual MeetingDecember 9- J3. 1995Washington Convention CenterWashington, DC

The thirty-fifth ASCB Annual Meeting will include symposia. mini symposia, poster sessions. special interestsubgroup meetings. special lectures. workshops, and other events that reflect the eclectic nature of cell biol­ogy and the tremendous impact of cell biology on all aspects of biomedical research. Each facet of the pro­gram incorporates venues designed to increase interaction among scientists and the exchange of ideasamong all participants.

EXHIBITSThe commercial exhibits will be open 9:00AM-4:00PM Sunday-Tuesday. December 10-12 and Wednesday.December 13 from 9:00AM-3:00PM. There will be approximately 450 exhibit booths, allowing registrantsthe opportunity to examine state-of-the-art products and seNices. The ASCB will provide complimentaryrefreshments each morning and afternoon in the exhibit hall.

For information contact:The American Society for Cell Biology

9650 Rockville Pike. Bethesda. MD 20814-3992FAX: 130 I) 530-7139 E-mail: ascbinfo@ascb.faseb.org

1052 Volume 103, Number 11, November 1995· Environmental Health Perspectives

World Health OrganizationInternational Agency for Research on Cancer (IARC)

IARC has an opening in its headquarters in Lyon. France. for the post of

Chief of the Unit ofCarcinogen Identificationand Evaluation

The main activity of this Unit is the production of the publication series IARC Monographs onthe Identification and Evaluation of Carcinogenic Risks to Humans. The Monographs programmehas provided reviews and evaluations of the evidence of carcinogenicity of about 800 chemicalsmixtures. exposure circumstances and biological agents. Three volumes of Monographs are pub­lished annually; each volume includes documents prepared by a Working Group of scientificexperts.

Applicants should have an MD. PhD. or equivalent in a field relevant to the Programme. a strongtheoretical background and significant experience in one or preferably several of the areas ofcancer epidemiology. cancer bioassays. toxicology and mechanisms of carcinogenesis. a solidunderstanding of all these areas and of their integration in the processes of cancer hazard identi­fication and risks assessment Good communication skills. ability to supervise staff. and ability tocoordinate working group meetings are essential. Training in epidemiology. biostatistics. scientificpublishing and experience in a national or international programme on carcinogenic hazardswould be desirable.

The incumbent is expected to plan. lead and coordinate the execution of the Unit's programmeswhich includes selecting topics for monographs. providing authoritative advice to the Director.IARC. on the selection and assignments of experts. serving as secretary to the monographsmeetings and being responsible for the production of high-quality monographs. He/she is alsoexpected to stimulate development and to initiate intramural and extramural research activities.

The initial appointment will be for two years. the first being probationary.The annual salary level is $53.611 US dollars tax-free at single rate and $57.806 US dollars for astaff member with dependents plus a cost of living element, which is currently 61 %of the abovefigures.

Those interested should write. enclosing a curriculum vitae. to:

Personnel OfficeIARC

ISO, Cours Albert ThomasF-69372 Lyon Cedex 08 France

FAX: (33) 72 73 83 35

Applications from women are encouraged.

New BooksAnother Turn of the Crank; EssaysWenrkll BerryWashington, DC: Counterpoint, 1995, 128 pp.ISBN: 1887178007 (alk. papet), $18.

Bioaugmentadon for Site RemediationExpansion ofPresentations Made at the ThirdInternational In Situ and On~Site BioreclamationSymposium, April 24-27, San Diego, CA.Columbus, OH: Battelle Press, 1995,276 pp.ISBN: 1574770047, $59.95.

Bioremediation of Chlorinated Solvents

Expansion ofPresentations Made at the ThirdInternational In Situ and On-Site BioreclamationSymposium, April 24-27, San Diego, CA.Columbus, OH: Barrelle Press, 1995,350 pp.ISBN: 1574770055, $69.95.

A Building Revolution; How Ecology and HealthConcerns Are Transforming Construction

David Malin Roodman, Nicholas LenssenWashington, DC: Worldwatch Institure, 1995,67pp. ISBN: 1878071254 (paper), $5.

Careers in the EnvironmentMichael Fasuw, Paul WalkerLincolnwood, IL: VGM Career Horizons, 1995,304 pp. ISBN: 0844244562 (hard), $16.95.0844244570 (paper), $12.95.

Clean Ships, Clean Ports, Clean Oceans;

Controlling Garbage and Plastic Wastes at SeaNational Research CouncilWashington, DC: National Academy Press, 1995.ISBN: 0309051371 (alk. paper), $42.95.

The Deep Ecology Movement; An Introductory

AnthologyAlan Drmgson, Yuichi Inoue, etis.Berkeley, CA: North Atlantic Books, 1995, 300 pp.ISBN: 1556431988, $14.95.

Ecology and Management ofNeotropicai

Migratory Birds; A Synthesis and Review ofCritical IssuesThomas E. Martin, Deborah M. Finch

New York: Oxford University Press, 1995. ISBN:0195084403, no price available.

Environment as a Focus for Public PolicyLynton, K CaldwellCollege Sration, TX: Texas A&M Univetsity Press,1995,310 pp.ISBN: 0890966435, $39.50.

Environmental Chemodynamics; Movement ofChemicals in Air, Water, and Soil

Louis j. ThibodeauxNew York: J. Wiley and Sons, 1995,640 pp. ISBN:0471612952 (clorh, alk. paper), $69.95.

Environmental Indicators; A Systematic Approach

to Measuring and Reporting on EnvironmentalPolicy Performance in the Context of SustainableDevelopmentAllen Hammond et al.Washington, DC: World Resources Institute,

1995,50 pp.ISBN: 1569730261, $14.95.

Encyclopedia of Environmental BiologyWilliam A. Nierenberg, ed.San Diego, CA: Academic Press, 1995. ISBN:0122267311 (vol. I A-E), 767 pp. ISBN:01 2226732X (vol. 2 F-N), 654 pp.ISBN:0122267338 (vol. 3 O-Z), 693 pp.$475 (ser).

Green Gold: Japan, Germany, the United Statesand the Race for Environmental TechnologyCurtis Moore, Alan MillerBoston, MA: Beacon Press, 1995,288 pp. ISBN:0807085308, $25.

In Situ Aeration: Air Sparging, Bioventing, and

Related Remediation Processes

Expansion o/Presentations Made at the ThirdInternational In Situ and On~Site BioreclamationSymposium, April 24-27, San Diego, CA.Columbus, OH: Battelle Press, 1995,634 pp.ISBN: 1574770039, $79.95.

Intrinisic Bioremediation

Expansion ofPresentations Made at the ThirdInternational In Situ and On-Site Biorrclamation

Symposium, April 24-27. San Diego, CA.Columbus, OH: Battelle Press, 1995,278 pp.ISBN: 1574770020, $59.95.

Mental Health and the Planned Environment;More Than Bricks and Mortar

David HelpernWashington, DC: Taylor & Francis Ltd., 1995.ISBN: 0748402357, (clorh, alk. paper), $79.0748402365 (paper, alk. paper), $24.95.

Methods in Plant Molecular BiologyPal Maliga et al.Cold Spring Harbor, NY: Cold Spring HarborLaboratoty Press, 1995,446 pp. ISBN:0879694505 (clorh), $110. 087969386X (paper),$75.

Molecular Biology and BiotechnologyRobert A. Meyers. ed.New York: VCH Publications, Inc., 1995, 1034pp. ISBN: 1560815698 (cloth), $149.95,1560819251C (paper), $59.95.

Ozone Layer Protection; Country IncrementalCostsKenneth King, Mohan MunasingheWashington, DC: Global Environmem Facility,1995. ISBN: 0821331337, $8.95.

The Safe Shopper's Bible; A Consumer's Guide toNontoxic Household Products, Cosmetics, and

FoodDavid Steinman, Samuel S. EpsteinNew York: Macmillan USA, 1995,352 pp.ISBN:0020820852, $15.

Supramolecular Chemistry

Jean~MarieLehnNew York: VCH Publications, Inc. 1995,271 pp.ISBN: 3527293116, $39.95.

American Occupational Health ConferenceAnnual Conference ofThe American Assocation ofOccupationalHealth Nurses, Inc. & the American College ofOccupational and

Environmental Medicine

1054

Aprll 26-May 3, 1996San Antonio ConventionCenterSan Antonio, Texas

For information:Nancy Kay Olson, Director ofConference &

MeetingsA'nterican Occupational Health Conference 55 w.

Seegers RoadArlington Heights, IL 60005

Volume 103, Number 11, November 1995 • Environmental Health Perspectives

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1-7 March. Fri-Thu. Viral Genome ReplicationTamanon. Colorado. Inforrn,uion: Keystone Symposia,Dr.lW« 1630, Silvenhome, CO 80498, (303) 262-1230,FAX (303) 262-1525

~ Much, Mon-Wul. Building Ene<gy. (In In<=ation>!SOW fJ<aric IlWIdings Confer.nce, 12m Ann.,.} QualilyBuilding ConFerence, and RENEW'96), Copley PiauHord, Boston, MassachusettS. Informalion: NortheastSustainable Energy Association, 50 Mib Sneet, Greenfidd,MA 01301, (413) 774-6051, FAJC(413) 774-6053

8-14 March, Fri-Thu. The ExtraceUular Matrix of Plants:Molecular, Cellular and Developmental Biology,Tamarron, Colorado. Information: Keystone Symposia,Drawer 1630, Silvenhorne. CO 80498. (303) 262-1230.FAX (303) 262-1525

I~14. March. Sun-Thu. Society ofToI.icology, AnaheimConvention Cemer. Anaheim California. Inform:;nion:Trish Strong Sociery ofToxicology, 1767 Business UntttOrin, Suitt 302, Reston, VA (703) 438-311 S. FAX:(703)438-3113

10-16, March, Sun-Sal. Posllranscriplional RNAProassing, Hihon Head Island. Soulh Carolina.Information: Keystone Symposia, Drawer 1630,Silvenhome, CO 80498, (303) 262-1230, FAX (303)262-1525

11-17 March, Mon-Sat. Molecular Basis for DrugResistancein Bacteria, Parasites and Fungi, Park City.Utah. Informacion: Key-SlOne- Symposia. Drawer 1630.Silvenhome, CO 80498, (303) 262-1230, FAX (303)262-1525

15-21, March, Fri-Thu. Signaling in NeuronalDevelopment, Differentation and Degeneration,Tamarron. Colorado. Informal ion: Keysrone Symposia,Dr.lw« 1630, Silvenhome, CO 80498, (303) 262-1230,FAX (303) 262-1525

17-23, March, Sun-Sat. SteroidlThyridlRetinoic AcidGene Family. Lake Tahoe. California. Information:Keyslone Symposia, Drawer 1630, Silverthorne. CO80498, (303) 262-1230, FAX (303) 262-1525

17-23, March, Sun-Sat. Transcriptional Mechanisms,Taos. New Mexico. Information: Keystone Symposia.Drawer 1630, Silvenhorne. CO 80498. (303) 262-1230.FAX (303) 262-1525

20-26, March, Wed-Tue. Lymphocyte Activation, HiltonHod Island, South Carolina. Keystone Symposia, Drawer1630, Savenhome, CO 80498, (303) 262-1230, FAX(303) 262-1525

25-31, March, Mon-Sun. Proteolytic Enzymes andInhibitors in Biology and Medicine, Keystone, Colorado.Keystone Symposia, Drawer 1630, Silverthorne. CO80498, (303) 262-1230, FAX (303) 262-1 525

26 March-I April, Tue-Mon. Immunopathogenesis ofHIV Infecrion, Hilton Head Island. Soulh Carolina.Keysrone Symposia. Drawer 1630, Silverthorne. CO80498, (303) 262-1230, FAX (303) 262-1525

27 March-2 April, Wed-Tue. Signal Transductionthrough Tyrosine Kinases, Taos, New Mexico. Keystone

Symposia, Drawer 1630, Silverthorne, CO 80498, (303)262-1230, FAX (303) 262-1525

31 March-3 April, Sun -Wed. American Sociery ofMechanical Engineers Solid Waste Processing DlvisionSeventeuth Biennial Conference. Trump RegencyHOlel, Atlanlic City, New Jersq. Infonnuion: RichardWill, The Coordinate Group, Inc.. Box 3356, Warrtmon,VA 22186-1956 (800)627-8913, FAX (703) 349-4540

April

14-I7April, Sun-Wed. Experimental Biology '96,Washington, DC Convention Center, Washington, DC.Information: FASEB Office of Scientific Meetings andConferences, 9650 Rockville Pike, Bethesda. MD20814-3998, (301) 530·7010, FAX (301) 530-7014

21-23 April, Sun-Tue. American Association for CancerResearch, Washingwn, DC Convention Center,Washington, DC. Information: MCR Public LedgerBuilding, Suite 816,150 South Independence Mall WestPhiladephia, PA 19106-3483 (215) 440-9300, FAX,(215) 440-9313

26 April-May 3, Fri-Fri, American Occupational HealthConference, San Anlonio Convention Cemer, SanAntonio, Texas. Information: Nancy Kay Olson,Direccor of Conferences & Meetings. AmericanOccupational Health Conference, 55 W. Seegers Road,Adingwn, Heigh", 1L 60065, (708) 228-6850, ext. 156,FAX (708) 228-1856

May

4-7 May, Sat-Tue. AnnuaJ Meeting of the Council ofBiology Editors, Ponland Hilton, Poreland, Oregon.Information: Cindy Clark, Council of Biology Editors.11 South LaSalle Street. Suite 1400, Chicago, IL60603-1210, (312) 201-6101, FAX (312) 201-0214

~10 May. Mon-Fri. 1996lntemational Conference onIncineration and Thermal Treatment Technologies,Savannah, Georgia. Information: lori Barnow,Office ofEnvironment Health, and Safety, University ofCaliromia, hvine, CA 92717-2725 (714) 824-5859

19-22 May, Sat-Wed. Founh International Symposiumon Metal Ions in Biology and Medicine,Tarragona/Barcdona, Catalonia, Spain. Information:Mercedes Gomez, Laboratory of Toxicology andBiochemistry, School of Medicine, elSan Lorenzo 21,43201 REUS, Sl"'in 34 77 759 376, FAX 34 77 759 322

20-22, May, Man-Wed. International Symposium onWork in the Information Society, Marina CongressCenter, Helsinki, Finland. Information: Work in theInformation Society, Finnish Institute of OccupationalHeal<h, Topdiuksenkatu 41 a A, F1N-00250 Helsinki,Finland, FAX, 358 0 4747 548. e-mai)',I;l@occupheahh.fi

June

2-6 june, Sat-Thu. ASBMB/ASIP/AAJ joint Meeting,Ernest N. Morial Convention Center, New Orleans,

Calendar

Louisiana. Information: FASEB OH'ice of ScientificMeetings and Conferences, 9650 Rockville Pike,B«hesda, MD 20814-3998. (301) 530-7010, FAX(301) 530-7014

July

14-17, july, Sun-Wed. The Coastal Society, FifteenthInternational Conference, Seattle, Washington.Information: The Coastal Society 15ch InternationalConference, clo Washington Sea Grant Program, 3716Bwoklyn Avenue, NE, Seanle, WA 98105, (206) 685­1108.

September

11-13 September, Wed-Frio Biological Monitoring inOccupational Environmental Health, Espoo, Finland.Information: Biological Monitoring, cia FinnishInstitute of OccupationaJ Health Symposium Sttretariat,Topdiuksenkaru 41 a A FIN-00250 Helsinki. Finland,358-0-47-471, FAX 35804747548

15-20 September. Sat-Fri, International Congress orO<:aJpationaJ Health. Stockholm, Sweden. Information:Arne Wennberg, Secretary General ICOH'96, Nationa.!Institute of Occupational Health, S-171 84 SOLNA,Sweden, 1+46) 8 730 91 00, FAX (+46) 8 82 05 56

October

20-24 October, Sun-Thu. Second World Congress onAhernatives and Animal Use in the Life Sciences,Uueclu, The Netherlands. Information: World CongressAlternatives 1996, FBU Congress Bureau, P.O. Box80.125, 3508 TC Utrecht, The Netherlands31.30.53.5044/2728 FAX 31.30.53.3667, e-maiLl.donkers@pobox.ruu.nl

December

7-11 December, Sat-Wed. Sixth International Congresson Cell BiologyrThirty.Sixth American Society for CellBiology Annual Meeting, Moscone Convention Center,San Francisco, California. Information: The AmericanSociety for Cell Biology, 9650 Rockville Pike. Berhesda,MD 20814-3992, (301) 530-7153, FAX (301) 530­7139, e-mail: ascb.info@ascbfaseb.org

1997

August

24-29 August, Sun-Fri. Seventeentb InternadonalCongress of Biochemimy and Molecular Biology 1997Annual Meeting American Sociel)' for Biochemistryand Molecular Biology, Moscone Convention Center,Sa.n Francisco,California. Information: CongressSecretariat, 17rh Imernariona.! Congress for Biochemislryand Molecular Biology, 9650 Rockville Pike, Bethesda,MD 20814-3996, FAX (301) 571-1824, ,-mail,171 UBMB@asbmbJaseb.o<g.

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Environmental Health Perspectives. Volume 103, Number 11, November 1995 1057

tivilY, should be submitted co the National Institutesof Drug Abuse, Mental Health, Ot Alcoholism andAlcohol Abuse by February I.Under this program. NIH institutes identify andsuppOrt exceptionally ralenred investigacocs who arewell established in theit fields, as a means of enhanc­ing those investigators' skills and dedication [0 theirareas of research.For copies of the program announcement, comaa: Dr.Etnestine D. Vanderveen, PhD, NlAAA, 6000Executive Blvd., Suite 402/MSC 7003, Bethesda, MD20892-7003. (301) 443-1273, FAX (301) 594-6043,e~mail: rvanderv@willco.niaa.nih.gov. Reference: PA~

95-051.

Great Lakes Protection Fund Call for

PreproposalsTo assist potential applicants in planning and coor­dinating gram requests, the Great Lakes ProtectionFund announces adoption of two fixed dates forsuhmission of preproposalo-January 2 and July I.The fund may also issue a limited call fot prepro­posals to target a specific wpic or topics within oneof rhe fund's four goals.The Fund's priority applicants ace nonprofit agen­cies; however, individuals and proprietary entitiesmay apply if a clear public benefit can be demon·strated and if financial benefits stemming from theproposed work accrue to the public good.Successful applicants must maintain open access toproject data, records and financial information.Results must be disseminated so that they are read·ily accessible to others.The two·page preproposal is the first of two stepsin the fund's proposal review process. The secondstep is an invitation to submit a full proposal basedupon favorable evaluation of the preproposal.Preptoposals are evaluated stricily against the fund'smission and must address one of the fund's lUur goals.

Proposed projectS must be appropriately collaborativeamong the private, public and independent sectors.The fund seeks ro supporr projectS which are supple­mental and non..<fuplicative of other effons. For multi­year projects, the fund may issue challenge grants to

encourage supplemental contributions.Staff reviews the preproposals and makes recom­mendations to the fund's grant making committeeof the Board of Directors. Preproposals are notsent to outside technical reviewers. Full proposals,however, are sent to at least three independenttechnical reviewers.Preproposals must be received in the office by 5:00pm Central Time, January 2, 1996. Preproposalsreceived after that date will be considered with pre­proposals submirred for the July I, 1996 deadline.Thtre are no exceptions to these deadlines.The fund also supports efforts to promote collabora­tion, coordination and regional action through plan­ning and discretionary travel grants. For more infor·mation on these grants, please contact the fund:Preproposal Application, Great Lakes ProtectionFund, 35 Easr Wacker Drive, Suite 1880, Chicago,II. 60601.

Magnetic Fields and Breast CancerStudies to evaluate the potential of 50 Hz magneticfields to promote mammary gland carcinogenesis inrats treated with dimethylbenzanthracene (DBMA)are needed over a 17-month performance period.This work will seek to replicate previously reportedstudies that magnetic fields increase breast cancer ratein DMBA-treated rats. For solicitation copy andmore information, reference RFP NIH·ES-95·31and contact: Jo Ann Lewis, Contracts andProcurement Management Branch, NIEHS, 79T. W. Alexander Dr., Bldg. 4401 ResearchCommons, PO Box 12874, Research Ttiangle Park,NC 27709, (919) 541-7893, FAX (919) 541-2712.

Fellowships, Grants & Awards

Metabolic EngineeringResearch that will expand the conceptual and experi­mental basis of metabolic engineering is sought bythe National Institute of Diabetes and Digestive andKidney Diseases.This initiative invites: (1) basic research that con·tributes to a quantitative understanding of the inte­gration and control of genetic, catalytic and transportprocesses that comprise metabolism; and (2) researchto create techniques that facilitate the exploitation ofmetabolic ptocesses for biomedical uses.Examples of more specific topics include: (l) deter­minants of lIux for metabolic pathways; (2) in-vivobehavior of metabolic enzymes and regulatory mole­cules; (3) such genetic tools as selective markers,reporter genes, vectors and regulatory molecules tointroduce targeted synthetic or regulatory capacityinto host cells; (4) creation of a broader range of hostcells fot introducing heterologous genes; (5) databas­es and computational tools for pathway analys~ andquantitative modeling of metabolism; (6) determi­nants of small molecule transport; and (7) systems(e.g., planrs, microbes) thar show potentially novelmetabolic capacity. Program deadlines includeFebruary 1and June I.For copies of the program announcement, contact:Warren Jones, Division of Pharmacology, Physiologyand Biological Chemisrry, N1GMS, 45 CenterDrive, MSC 6200, Bethesda, MD 20892-6200.(301) 594-5938, FAX (301) 480-2802, e-mail:JONESW@gml.nigms.nih.gov or CarherineMcKeon, Division of Diabetes, Endocrinology andMetabolic Diseases, NIDDKD, 45 Center Drive,Room 5AN-18B-MSC 6600, Bethesda, MD20892-6600. (301) 594-8810, FAX (301) 480-3503,e-mail: McKEONC@ep.niddk.nih.gov. ReferencePA 95-087.

Back Issues ofEnvironmental Health Perspectives Supplementsare available FREEfrom NIEHS

Volume 102, No. 12Volume 102, No. 11Volume 102, No. 10Volume 102, No.9Volume 102, No, 8Volume 102, No, 7Volume 102, No, 6Volume 102, No, 5Volume 102, No, 4

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Genetic and Molecular EcowxicologyDosimetry for Risk AssessmentOxygen Radicals and Lung InjuryToxicological Evaluation of Chemical InteractionsBiostatistics in the Study of Human CancerHealth Effects of BoronCarcinogenic and Mutagenic N-Substituted Aryl CompoundsBiopersistence of Respirable Synthetic Fibers and MineralsRisk Assessment of Urban Air: Emissions, Exposure, Risk Identification, and

Risk QuantitationMolecular Mechanisms of Metal Toxicity and CarcinogenicityBiostatistics in the Study ofToxicology

To order a copy, write: Supplement Circulation/Environmental Health Perspectives, Nationallmtitute ofEnvironmental HealthSciences, PO Box 12233, Research Triangle Park, NC 27709 orfax 919-541-0273.

Environmental Health Perspectives. Volume 103, Number II, November 1995 1059

Ion Homeostasis and CeU Injury (HNV95)Changes in ion transport and homeoscasis appear to

be involved in apoprotic cell death. Studies focus onmeasuring changes in intracellular calcium, pH, sodi­um and magnesium in isolated cells using fluorescentindicators in cells stimulated to undergo apoptosis.Alterations in signal transduction pathways which areresponsible for the ionic alternations are also undersmdy. Applicants must have experience in ion mea­surements using fluorescent indicators or experiencewith cell culture Ot molecular biology.Contact: Elizabeth Murphy. (919) 541-3873.Laboratory ofMolecular Biophysics, Maildtop 17-05.

Molecular Dosimetty and Epidemiology(HNV96)Knowledge and techniques in molecular biology areapplied to investigations designed [0 determine effectsof low-dose exposures to environmental agents.Animal models. cell systems and human samples areused. Studies encompass mutation analys~ and signaltransduction elements.Contact: George W. Luciet. (919) 541-3802, labora­tory of Biochemical Risk Analys~. Maildrop A3-02.

Molecular and CeUuIar Biology (HNV97)The action and function of several nuclear (orphan)receptors in the regulation of gene expression and dif­ferentiation are being investigated. Studies involvecharacterization of response elements, interaction withother transcriptional factors and gene knockouts.Applicams must have training in molecular biologytechniques.Contact: Anton Jetten. (919) 541-2768, Laboratoryof Pulmonary Parhobiology. Maildrop 02-01.

Mechanisms by Which Organisms Produa:Mutations (HNV99)Studies are aimed at understanding the mechanismsby which organisms produce mutations. Specific pro~

jeets involve the isolation and molecular characteriza·tion of antimutator mutants in the bacterium E (o/~

the genetic and biochemical analysis nf DNA replica­don fideliry in this organism; and a structure-functionanalysis of the dnaE and dnaQ genes (encoding,respectively. the DNA polymerase and exonucleolyticproofreading activiry).Conract: Roel M. Schaaper. (919) 541-4250.Laborarory of Molecular Genetics, Maildrop E3-01.

Mechanisms ofDNA Replication (HNVlOO)The regulation and mechanism of human DNA poly­merases involved in the replication of nuclear andmitochondrial DNA is being investigated. Attentionis on the mutation rate of the mirochondrial andnuclear genome by understanding rhe enzymology ofthe mirochondrial and nuclear DNA polymerases.Future studies will include the regulation of theseessential enzymes in the cell.Contact: William Copeland. (919) 541-4792.Laborarory ofMolecular Genetics. Maildtop E3-01.

Reproductive Biology and Toxicology(HNVI04)The molecular events underlying the abnormal devel~

opment of the reproductive system associated withexposure to xenobiotic estrogens such as diethylstilbe­strol (DES) are being investigated. Particular interestis the biochemical and molecular analysis of transientand permanent alterations in the estrogen-responsive

(e.g., lactoferrin) and metabolizing (e.g., sulfotrans-­ferase) genes and the implications for human healthdisease.Contact: Masahiko Negishi. (919) 541-2404,Laboratory of Reproductive and DevelopmentalToxicology. Maildrop E4-07.

Ceo Adhesion in Metastasis (HNVI05)The molecular mechanisms by which cancer cellsmetastasize are being studied, focusing on the roles ofcell surface teceptors and cell adhesion. Special inter~

ests include the effects ofswainsonine, an inhibitor ofprotein glycosylation, on tumor cells and thehematopoietic system. Candidates should have exper­tise in cancer biology, molecular biology and bio­chemistry.Conract:John Roberts. (919) 541-5023. LaboratoryofMolecular Carcinogenes~, Maildrop 0-14.

Molecular Mechanisms of Respiratory Diseases(HNVIIO)This is a tenure track position to develop an indepen­dent research program in cellular and molecularmechanisms of respiratory biology and diseases.Extensive postdoctoral experience in molecular biolo~

gy, developmental biology, signal transduction or bio~

chemical mechanisms of inflammation is required.Conract: Paul Nettesheim, (919) 541-3540.Labotatnry of Pulmnnary Pathobinlogy. Maildtnp02-01.

Epitope Mapping (HNVI I I)Mass spectrometry combined with proteolytic footprinting is being used to determine conformationalepitopes of recombinant HIV proteins towards mono~clonal antibodies. Candidates should have primaryexperience in protein chemistry, including affinitytechniques and proteolytic techniques.Conract: Kenneth Tomer. (919) 541-1966,Laboratory or Molecular Biophysics. Maildtop 6-0 I.

Molecular Biology and Fatty Acid Biochemistty(HNVII2)Novel human eytochtnme P450 enzymes that metab­olize fatty acids are cloned and expressed, and rhe car­alytic properties of the recombinant, purified proteinsare evaluated by HPLC and GC/MS. The P450enzymes are localized to specific cell types byimmunohistochemistry and in situ hybridization andthe regulation of P450 gene expression is studies usingNorthern blor analysis. RT-PCR and proteinimmunoblotting. Applicants should have a strongbaekgtnund in cell and molecular biology.Contact: Darryl Zeldin, (919) 541-1169, Lahoratoryof Pulmonary Parhobiology. Maildrop 02-01.

Laboratory of Reprodnctive and DevelopmentalToxicology (HNVII4)An independent program of basic research in the fieldof developmental biology relative to studies in repro­ductive biology, developmental toxicology, hormonemechanisms, signal transducrion. cell gtnwth and dif­ferentiation, apoptosis, gene regulation and cancerbiology will be iniriated. Applieanrs with the porenrialfor creative research in developmental biology who arestudying cellular and molecular mechanisms of mam~malian development desired.Contact: Kenneth Korach, (919) 541-3512,Laboratory of Reproductive and DevelopmentalToxicology, Maildtnp B3-02.

Position Announcements

Gametogenesis (HNVI16)Genes with stage~specific expression during spermato­genesis are studied to define intrinsic and extrinsicmechanisms regulating development and function ofmale gametes. We use transgenic mice to dissect pro~

moter regions and gene knockout mice to define theroles of gene products in meiotic and post~meiotic

processes. Strong background in cell and molecularbiology required.Contact: E.M. Eddy. (919) 541-3015, Laborarory ofReproductive and Developmental Toxicology,Maildrop C4-0 I.

Signal Transduction (HNV1 17)Studies include receptor mechanisms, G~proteins,

inositol phosphates, calcium signaling, ion channels,cell growth and differentiation, apoptosis, gene regu­lation and cancer biology. Priority will be given toapplicants utilizing cellular and molecular approachesto study intermediate steps in signal transductionpathways such as phosphorylation-dephosphorylationcascades.Contact James Pumey. (919) 541-1420, Laboratoryof Cellular Molecular Pharmacology. Maildrop 19­01.

MolecnIar Biology of Renal Transport(HNVII8)Renal organic anion and cation secretion mediateelimination of toxic chemicals. Current projects usecultured epithelium, membrane vesicles and imagingto examine control of secretion and coordination ofintracellular and membrane events during secretion.Expression cloning of secretory transport proteins hasbegun. Amolecular biologist desired.Contact: John B. Pritchard, (919) 541-4054,Laboratory nf Cellular and Molecular Pharmacology,Maildrop 19-0 I.

Molecular Biomarken of Risk (HNVI 19)Molecular epidemiologic studies of gene~environmentinteraction. Development and application of methodsfor detecting somatic mutation and germline poly~

morphism in genes that modulate exposure, DNAdamage and disease in human population studies.Candidates should have molecular biology experience.Conract: Douglas A. Bell, (919) 541-7686.Laboratory of Biochemical Risk analysis, MaildropC3-03.

Ion Channel Ph}'5iology and Modniation(HNVI20)Ligand-gated (serotonin 5-HT3 and gluramate) andvoltage-gated calcium channels are studied in neuronsand cell lines, as well as channels expressed in mam~

maHan cells or Xenopus oocytes. Strucrure~function

aspects of theses channels are investigated, as well ashow intracellular signal transduction pathways modu­late the physiological properties of these channels.Applicants must have e1ecrrophysical (preferablypatch~clamp) experience. Experience in molecularbiological techniques would be a great asset.Cnntact Jerrel L. Yakel, (919) 541-1407, Laboratoryof Cellular and Molecular Pharmacology, Maildrop19-04.

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Editorial Policy _EnvironmtnW H(iJlth Pmpectives is intended to be aforum fot the discussion of issues in environmentalhealth. and several formats have been devised forthat purpose. In addition, several formats are avail­able for the publiOltion of scientific articles and sci­entific discussion. All scientific articles are subjea torigorous peer review. The primary criteria for publi­Olcion are environmental sigoifiClllce and scientificquality.

Environmental science is made up of manyfields. and therefore we are prepared to considerscientific progress in all of them. Cross-feniliza­tion and serendipity have proven to be exrremdyimponant processes in the advance of science ingeneral, and this must hold true for the science ofenvironmental health. We will consider for publi­Oltion anicles ranging from the most basic molec­ular biology to environmental engineering. Wepanicularly encourage those teseatchers concernedwith mechanisms of toxic action and newapproaches for detecting andlor remedying envi­ronmental damage.

Opinions and ideas based on scientific obser­vation and argument are welcome. While theexpression ofopinions may lead to debate and dis­agreement, such teactions are healthy and can leadto new research and discoveties. Presentations ofideas and opinions will be promoted. but our pol­icy will be to srrive for objectivity and balance.

In addition to scientifIC anides and discussion.we publish news of the environment We will con­sidet factual articles about issues that affect theenvironment and human health. We summarizelegislative and regularory developments. grantinformation from NIEHS and other grantingagencies, new research areas, environmental prol>­lems. technological advances. and informationabout the National Toxicology Program and otherimponant programs. Presentations of news strivesfor objectivity and balance and is based on thestrength ofscientific evidence.

Our current policy is to give the correspond­ing aurhor of each published article 200 fteereprints.

PERSPECTIVESThe journal is a forum for the expression of ideasand opinions. Opinions and ideas should becarefully consideted and based on scientific prin­ciples. Three formats are offered:

EDITORIAL statements are published by oureditors. members of our editorial boards, andoccasional guest editors. These statements areintended to focus anention on important orneglected areas of environmental health. offeropinions and ideas. and stimulate discussion.

COMMENTARIES are up-to-date articles thatmay ptesent commentaries offering perspectiveand insight on a panicular topic. Commentariesare subject to peer review.

CoRRESPONDENCE is encouraged. Opinions.perspectives, and insight are welcome. Com­ments on articles published in EnvironmtntalHealth PmpectivtJ are also welcome, but eriticismwill always be balanced by the opporrunity fordefense and c1arifiOltion. .

RFsEARCHTo ensure fairness in the review process, we rou­tinely seek opinions from three reviewers.Suggestions for reviewers of manuscripts will beconsidered. The research portion of the journalconsists of four formats:

RESEARCH ARTICLE.S are original manuscriptsreporting scientific research and discovery in thebroad field ofenvironmental health. Research arti­cles may come from any field of scientific research.from the mOSt basic molecular biology and bio­chemistty to atmospheric physics. ecology. andengineering. The criteria for publication ateweighted toward scientific quality and enviton­mental significance. The work will be assessedaccording to its originality. scientific merit, andexperimental design; the manuscript will be evalu­ated based on its conciseness, clarity. and presenta­tion. We also attempt to address certain ethicalproblems duting the teview process. We requireassurances that all human and animal subjects havebeen lteated humanely and with due regard for thealleviation of suffering. Manuscript review alsoconsiders scientific integrity as pan of the process.

RESEARCH ADVANCES are concise articlesintended to address only the most recent develop­ments in a scientific field. Clarity of presentationis of primary importance beCluse these articles areintended to be educational though targeted to theexperr audience.

REVIEWS are nartowly focused arricles thatemphasize recent developments in a panicuIar fieldof research. lengthy hisrorical perspeccives are norappropriate.

MEETING REPORTS are shorr summaries ofconferences. symposia, or workshops in whichthe scientific objectives and achievements of ameecing are described.

ENvIRONEWSThe news section provides up-to-date infounationon imporrant issues in environmenral health cov­ering a variety of areas including policy. legisla­tive, and regulatory actions; innovative technolog­ical and conceptual research advances; conferenceand meeting summaries; and emerging environ­mental problems. The news seerion consists ofseveral components:

FORUM anicles are brief repons on maltets ofpotential environmental health signifiClllce such aschemical spills and contamination episodes. Briefreviews ofrecent scientific advances are also included.

NIEHS NEWS summarizes signifiClllt activi­ties or accomplishments at NIEHS and theNational Toxicology Program.

Focus articles are substantive news itemsahour important issues in environmencal health.Examples include repons on risk assessment, riskmanagement dilemmas. women's health initia­tives, environmental equity. relevance of animalmodels to toxicity testing. and structure-activityapproaches to toxicity evaluation.

SPHERES OF INFLUENCE is a legal/reguIatorycolumn that presents repoctS on significantevents and decisions involving the executivebranch. Congress, and regulatory agencies.Examples include new directions of White

House policies, impact of Clean Air Act legisla­tion, and coverage of congressional hearings onenvironmental health issues.

INNOVATIONS presents emerging opporruni­ties in environmencal health based on new dis­coveries or approaches in biology. chemistry.engineering. or information sciences. Examplesinclude the use of transgenic animals in toxicitytesting. new advances in molecular biology,development of more rapid and efficient meth­ods for clean-up of hazardous wastes, and meth­ods for early detecrion of environmenraI damageand environmentally mediated diseases.

ANNOUNCEMENTS includes a calendar ofupcoming events such as conferences, work­shops, and public hearings. Appropriate listingsare made for industrial, academic, regulatory.and legal activities. This seerion also includes list­ings of fellowship and grant announcements andpositions available.

ENVIRONMENTAL HEALTII PERSPECTIVESSUPPLEMENTSDuring the last 20 years, we focused on thedevelopment of a series of monographs that havegenerally arisen from symposium ot conferenceproceedings. Monographs are now published assupplements to the main journal. Six to eightsupplements are published per year: four to sevenof these consist ofconference. workshop, Ot sym­posium proceedings. and one issue is dedicatedto solicited and unsolicited comprehensivereviews on environmental health. Conferencemanuscripts must be of the highest scientificquality and are subject to rigorous peer review.Manuscripts that do not meet EHP standards arenOt published.

Each supplement resulting from aconferenceshould address a specific area of concern. aresearch problem, or a panicular scientific issue.Supplements are. in general, dedicated to scien­tific issues and not to programmatic themes.Each supplement should form a landmark state­ment for a panicular subjea and must be an up­to-clate, balanced source of reference material forresearchers, teachers, legislators, and theinformed public. PubliOltion of conference pro­ceedings in EHP Suppkmtnt5 requires the suI>­mission ofa proposal as desctihed in Instructionsto Authors.

SUPPLEMENT ARTICLES from conferences aregenerally the result of research investigations.reviews. or a combination of both; however, briefrepons and commentaries are also approptiate.

PERSPECTIVE REVIEWS are targeted to the oneor cwo specific issues of EHP Supplements setaside for the publication of reviews in enviton­mental health sciences. Perspective teviews arein-depth, comprehensive articles that addtessdevelopments in specific ateas. Perspectivereviews must not be simply a compilation of theliterature but should be scholarly. landmatkstatements offering a complete and balanced per­spective as well as insight into the environmencalsignifiClllce of the research.

1064 Volume 103, Number 11, November 1995. Environmental Health Perspectives

Instructions to AuthorsEnvironmental Health Perspectives covers all disci­plines engaged in the broad field ofenvironmen­tal health. Aurhors should therefore write in aclear and simple manner, avoiding unnecessarytechnical jargon, so that the article is understand­able ro readers in other disciplines.

All submitted manuscripts are acknowledgedupon receipt and subjected to three independentpeer reviews. Submir four copies of the manu­script, along with three sets of publication-quali­ry figures. Authors may suggest reviewers whensubmitting a manuscript, although suggestedreviewers may not be chosen. Peer review is gen­erally completed within four weeks and authorsare notified of necessary revisions or rejection ofthe manuscript. Revisions are requested withinthree weeks of notification. Aurhors must submittwo copies of the revised manusctipt, a letterresponding to reviewer's comments, and adiskette containing the revised manuscript.Articles are generally published three monthsafter receipt of revisions. Corresponding aurhorsare sent 200 free reprints of their article uponpublication.

MANUSCRIPT PREPARATION

All manuscripts must be ryped, double-spaced, inEnglish, on only one side of the paper. Type thearticle on white paper, 216 x 279 mm (8.5 x 11in) or ISO A4 (212 x 297 mm), with margins ofat least 25 mm (l in). Number pages consecurive­Iy, beginning with the title page. Reference lists,tables, and figure legends should be on sepatatepages, and should also be double-spaced. If themanuscript is accepted for publication, a comput­er disk copy must be submitted along with twohard copies of the revised manuscript.

Titles should not exceed 20 words and shouldgenerally not contain abbreviations or numericalvalues. The title page should also list authors (firstor second names spelled out in full), full addressof the institution where the work was done, andaffiliation of each author. Indicate aurhor towhom galley proofs and reprints should be sent(include complete address for express mail service,telephone and FAX numbers).

Place a running title, nor to exceed 50 charac­ters and spaces, on the second page of the manu­script. Also on this page, list 5-10 key words forindexing purposes, lisr and define all abbrevia­tions, and include acknowledgments and grantinformation, not to exceed 50 words. Nomen­clature and symbols should conform ro the rec­ommendations of the American Chemical Societyor the International Union of Pure and AppliedChemistry (IUPAC).

All articles except meeting reports and com­mentaries must include an abstract, not to exceed250 words, which should be placed on rhe rhirdpage of the manuscript. Do not include details ofmaterials and methods or references in theabstract.

Text should begin on the fourth page. Forresearch involving human subjects, include a stat­ment that informed consent was obtained. For

animal subjects, include a statement that care andtreatment was conducted in accordance withestablished guidelines. Concise headings (not toexceed 8 words) may be used to designare majorsecrions. Recommended headings, where appro­priate, are "Materials and Merhods," "Resulrs,"and "Discussion" or "Conclusion." Referencesmust be listed by number, in order of citation.Reference numbers should be italicized, if possi­ble, and placed in parentheses in the text.

The reference list should begin on a separatepage. Personal communications, unpublishedobservarions, manuscripts in preparation, andsubmitted manuscripts should not be included inthe reference list, nor should explanatory text(foomotes). Such references should be inserted atappropriate places in the text, in parentheses,without a reference number. "In press" articlesshould be included in the reference lisr.Abbreviate journal names according to IndexMedicus or Serial Sources for the BIOSIS PreviewsDatabase. List all authors and editors; do not useet al. in the bibliography. Include rhe title of thejournal article or book chapter and inclusive pagi­nation. For reports, include the authoring organi­zarion, report number, "publisher" and location,and year of publication. Some examples are shownbelow:

Journal Article:1. Canfield RE, O'Connor JF, Rirken S, Kirchevsky

A, Wilcox AJ. Development of an assay for abio­marker of pregnancy in early feral loss. EnvironHealth Petspeer 74:57-66 (1987).

Book Chapter:2. Lohman AHM, Lammers AC. On the structure

and fiber connections to olfacrory centers inmammals. In: Progress in brain research: senso­ry mechanisms, vol 23 (Zonerman Y, 00). NewYork:Elsevier, 1967;65-82.

Report:3. U.S. EPA. Status of pesticides in reregistration

and special review. EPA 738-R-94-008.Washington, DCEnvironmental ProrecrionAgency, 1994.

Each table must be on aseparare page. Tablesshould be numbered with Arabic numerals, fol­lowed by a brief title (not to exceed 25 words).General foomotes to tables should be indicated bylowercase superscript letters beginning with a foreach rable. Foomotes indicating statistical signifi­cance should be identified by asterisks (', ") anddaggers (t, t). Type foomotes directly after thetable. Tables should contain no more than threelayets of column headings, and the entire tableshould fit on one journal page.

Figure legends should be typed, double­spaced, on a separate page. Legends should be asbrief as possible without compromising explana­tion of the figure. Use Arabic numerals to numberfigure legends. Define any abbreviations in thelegend on first mention.

Three sets of publication-quality figures mustbe submitted. Electronic versions of figures areencouraged, but should be submitted in additionto, not in lieu of, hard copies of the figures. Dotmatrix computer drawings are not acceptable as

original art. The style of figures should be uni­form throughout the paper. IdentifY all figures onrhe back with the authors' names and figure num­ber and indicate orientation. Label axes of graphsclearly and define all symbols used.

Marerial suitable for inclusion as on-line doc­umentation, such as kinetic studies, is welcome.Contact the EHP office for instructions regardingsubmission.

Electronic copies of accepted manuscripts arerequired. We prefer 3.5-inch diskettes, Macintoshplatform, Microsoft Word, but IBM PC-compati­ble files are acceptable. The file should contain aUparts of rhe manuscript in one file. Label rhediskette with title, aurhor, manuscript number,and software used. Diskettes are not returned toaurhors. Electronic files created by word proces­sors or similar equipment are not acceptable.

ENVIRONMENTAL HEALllI PERSPECTIVESSUPPLEMENTSSUPPLEMENT MANUSCRIPTS result from confer­ences, symposia, or workshops and may take sev­eral forms. 1) Manuscripts teporting originalresearch should be formatted as described forResearch Articles, 2) opinions and discussionabout a particular topic should be formatted asdescribed for Commentaries, 3) manuscriptsreviewing a topic or reporting a combination ofreview and original research should be formattedas described below for Perspective Reviews.

PERSPECTIVE REVIEWS are in-depth, compre­hensive reviews of a specific area. They shouldbegin with a title and second page as describedfor research articles. Introduction and presenta­tion of information should be continuous wirhspecific items and discussion indentified by usingsubheadings. Absttacts, references, abbreviations,figures, and tables should also be handled asdescribed for research articles.

PROPOSAlS for the publication ofconference,symposium, and workshop proceedings will beconsidered; however, space is limited. We turnaway many excellent proposals simply becausewe do not have space to publish them.

All proposals are reviewed and examinedwith a number of specific questions in mind. Indeveloping a proposal, consider the following:Proposals are assessed according to their original­ity and scientific merit. Is the supplement need­ed? Is rhe subjecr matter timely and potentiallyuseful to workers in the field? What is the envi­ronmental significance of the topic beingaddressed? Is the proposed supplement a com­plete representation of rhe field? Are there otheraspects that should be included? Does the pro­posal comain sufficient information for evalua­tion? Is the presentation clear? Can the organiz­ers integrate rhe participants into acohesive unit?Are rhe contributors appropriate for the topiclisted and do they have sciemific credibility?

The source of funding is also considered.Scientific objectivity is extremely important, andit must be clear that organizers are not beingused to present a bias favored by the fundingbody. Contributions from an interested party toa conference need not disqualifY a proposal, but

Environmental Health Perspectives • Volume 103, Number 11, November 1995 1065

Instructions to Authors

it is appropriate that the major source of fundingbe from a disinterested source or that organiza­tional safeguards be set in place to minimize theintrusion of institutional bias.

All proposals must be submitted at least sixmonths in advance of the conference. In thepublication ofconference proceedings, timelinessis essential. Because it takes at least six months topublication, no proposal will be considered afterthe conference has been held.

SUBMISSION OF MANuSCRIPTS ANDPROPOSALSSubmit all manuscripts and proposals in quadru­plicate roo

Editor-in-ChiefEnvironmental Health PerspectivesNarional Institute of Envitonmental

Health SciencesPO Box 12233III Alexander DriveResearch Triangle Park, NC 27709 USA

In your covering letter please provide assurancesthat the manuscript is not being considered forpublication elsewhere and that all animals usedin the research have been treated humanelyaccording to institutional guidelines, wirh dueconsideration to the alleviation of distress anddiscomfort. If the research involved human sub­jects then a statement must be made to theeffect that participation by those subjects did

not occur until after informed consent wasobtained.

Permission to reprint figures or tables fromother publications must be obtained by theauthor prior to submission of the manuscript.

Finally, a statement must be made indicat­ing that all authors have read the manuscriptand are in agreement that the work is ready forsubmission to a journal and that they accept theresponsibility for the manuscript's contents.

Inquiries may be made by calling (919)541-3406 or by FAX at(919) 541-0273-

SUBMISSION OF NEWS INFORMATIONEnvironmental Health Perspectives welcomesitems of interest for inclusion in the Envir­onews, Calendar of Events, and Announ­cements sections of the journal. All items arepublished subject to the approval of the Editors­in-Chief. All submission for these sectionsshould be sent to the attention of:

News EditorEnvironmental Health PerspectivesNational Insritute of Envitonmental

Health SciencesPO Box 12233III Alexander DriveResearch Triangle Park, NC 27709 USAItems submitted for inclusion in the Forum

sectinn must not exceed 400 words. Items may beedited for style or content, and by-lines are not

attached to these articles. If possible, items shouldbe submitted on computer disk usingWordPerfect or Micrnsoft Word, in straight textwithout formatring.

Items received for rhe Calendar of Eventswill be published in as timely a manner as possi­ble, on a space-permitting basis. Submissionsshould include all relevant information aboUl thesubject, date, time, place, information contact,and sponsoring organization of the event.

Position announcements will be limited toscientific and environmental healrh posirions andwill be run on aspace-permitting basis. Althoughwe seek to publish all appropriate announce­ments, the timeliness of publication cannot beguaranteed.

Public information advertisements will berun free-okosr as space becomes available. Allads are run subject to their appropriateness tothe editorial format of the journal. Submissionsof advertisements should include full-page,half-page, and quarter-page formats if available.Ads should be camera-ready, black and whitepositives.

Persons interested in free-lance wriringopportunities with Environmental HealthPerspectives should submit acover letter, resume,and writing samples to the address above. Forinquiries call the news editor at (919) 541-5377.

1066 Volume 103, Number 11, November 1995· Environmental Health Perspectives