Heafth Hazards from Volcanic Gases: A Svstematic

Literature Review

ANNA HANSELTDepartment of Epidemiology & Public Healthlmperial College LondonLondon, UKCTIVE OPPENHEIMERDepartment of GeographyCambridge UniversityCambridge, UK

AT LEAST 455 mil l ion people worldwide l ive withinpotential exposure range of a volcano that has beenactive within recorded history.t Volcanoes and geother-mal areas are associated with emissions of a variety ofgases that typical ly include carbon dioxide (COz); sul furdioxide (SOr); hydrogen chlor ide (HCl); hydrogen f luo-r ide (HF); hydrogen sulf ide (HrS); carbon monoxide(CO); radon (Rn); and heavy metals including lead andmercury.2,3 Emissions may occur in associat ion witheruptions of all sizes. They are also common betweeneruptions on many volcanoes, where they can be vent-ed from fumarole fieldsa or diffusely through the soil.5-7Cas fluxes can be substantial in terms of atmosohericsource strengths. For example, the mean SO2 flux fromMt. Etna in Sici ly is equivalent to the total of anthro-pogenic SO, emissions from France, making i t arguablythe world's largest sustained point source emitter ofSO2.B Annual emissions from volcanoes in Japan approx-imately equal those from anthropogenic activities inJapan.e Of particular note at present is Miyakelima vol-

628

ABSTRACT. Millions of people are potentially exposed to volcanic gases worldwide, andexposures may differ from those in anthropogenic air pollution. A systematic literature reviewfound few primary studies relating to health hazards of volcanic gases. SO, and acid aerosolsfrom eruptions and degassing events were associated with respiratory morbidity and mortal-ity but not childhood asthma prevalence or lung function decrements. Accumulations of HrSand CO2 from volcanic and geothermal sources have caused fatalities from asphyxiation.Chronic exposure to H2S in geothermal areas was associated with increases in nervous sys-tem and respiratory diseases. Some impacts were on a large scale, affecting several countries(e.9., laki fissure eruption in lceland in 1783-4). No studies on health effects of volcanicreleases of halogen gases or metal vapors were located. More high quality collaborative stud-ies involving volcanologists and epidemiologists are recommended.<Key words: air pollution, acid aerosols, carbon dioxide, hydrogen sulfide, l i terature review,risk assessment, sulfur dioxide, volcanic eruption>

cano, where the SO, flux peaked at over 100 kilotonnesper day in 2000 and has remained above 5,000 tonnesper day since.l0 Despite their use of "natural" energysources, geothermal power stations also contribute sig-ni f icant ly to air pol lut ion; sul fur, CO2 and mercury emis-sions from some geothermal power stat ions areequivalent to those from fossil fuel power stations.11,12Addit ional ly, volcanic emissions may contr ibute sub-stant ial ly to urban air pol lut ion in some ci t ies. For exam-ple, concentrations of SO, and sulfate in Mexico Cityare significantly elevated when affected by emissionsfrom the Popocat6petl volcano.13,1a

Studies assessing volcano-related mortality from his-torical and contemporary eruptions suggest that vol-canic gases account for < 13'15 1e 4oh16 of recordeddeaths from volcanoes. This is likely to be an underesti-mate. Such studies general ly focus on erupt ions,neglecting volcanic degassing apart from eruptive activ-i ty. Addit ional ly, the extent of dispersion of volcanicgases is not always appreciated. For example, Blong3

Archives of Environmental Health

refers only to the deaths from starvation resulting fromthe major erupt ion of Laki in lceland in 17834, where-as recent work suggests that there may have beenimportant impacts on mortal i ty as wel l as morbidi ty inareas o f nor thern Europe, inc lud ing the Un i tedKingdom.B, l7

There is now an extensive bodv of literature on thehealth effects of air pol lut ion of anthropogenic or igin.Most of these exposures actually involve a complexmixture of organic and inorganic gases, plus a var iableparticulate fraction with both organic and inorganiccomponents.ls Mixtures from anthropogenic sources areusual ly di f ferent from those in volcanic gases, and i t isunclear whether the dose-response coefficients can bedirect ly transferred to volcanic emissions. Addit ional ly,human exposures to very high concentrations of somevolcanic gases such as hydrogen sulf ide or CO, areuncommon, and information from occupat ional studiesmay not ful ly descr ibe effects in a general populat ion.Also, people's behavior dur ing volcanic episodes mayeither reduce their expsosure to volcanic gases (e.g.,taking shelter indoors) or increase i t (e.9., volcano sight-seeing), making comparabi l i ty with studies of currenturban exoosures more di f f icul t .

In this review, we aimed to ident i fy al l pr imary cl in i-cal and epidemiological studies to better synthesizewhat is known about the human health effects of vol-canic gases and to identify areas for further study. Theterm volcanic gases has been used, and single pollutantgases have been discussed throughout, consistent withthe simplification of gas chemistry in health effect stud-ies relat ing to anthropogenic pol lut ion.

Method

A l i terature search was conducted using biomedicaljournal databases Medl ine (Ovid 1966 to end 2003) andEmbase (1988 to end 2003), the lSl Web of Science(1981 to end March 2004), and the geological databas-es CeoRef (1785 to end March 2OO4) and CEOBASE(1990 to end February 2OO4). Medl ine is a bibl iograph-ic database produced by the U.S. Nat ional Library ofMedicine covering approximately 4,500 journal t i t les,whereas EMBASE is a bibl iographic database producedby Elsevier Science in the Netherlands covering approx-imately 4,000 journals with a more European focus thanMedl ine. Thomson lSl Web of Science includes search-es of databases of the Science Citation lndex, the SocialSciences Citation Index, and the Arts and HumanitiesCitation lndex (all 1981-). CeoRef is a bibliographicdatabase for the geosciences published on the Web byCommunity of Science, Inc. l t contains references toarticles, books, maps, conference papers, reports, andtheses, covering the geology of North America from1 785 and for the rest of the world from 1933. CEOBASEis produced by Elsevier Science Publ ishing and covers

December 2004 [Vol. 59 (No. 12)]

the literature on geography, ecology, geology, oceanog-raphy, geomechanics, and developmental studies.

Biomedical journal searches used the textwords "vol-can$" or "geothermal ," and studies were limited tothose in humans. Web of Science, CeoRef, andCEOBASE sessions searched article title, keywords, orabstract for the phrase:

(volcan* and gas* and [death* or died or ki l l * or mor-bidi ty or mortal* or respir* or asthma* or health or can-cer* or carcinogen* or al lerg*J).

All titles and abstracts were read, and potentially rel-evant studies with at least an abstract in English wereobtained. Articles relating solely to health effects of vol-canic ash part iculate air pol lut ion were not included buthave been recently reviewed by Horwell and Baxter.lePapers relat ing to indirect ef fects on human health, e.9.,through effects on vegetation, animal health, or onozone layer depletion as a consequence of stratosphericemissions of SO2 were also excluded. Addit ional infor-mation was obtained from references in papers identi-fied by the literature searches, the authors' own files,from col leagues, from reports on nat ional volcanoobservatory web sites, observatories, and from theinternet.

Papers were defined as primary studies if they con-tained epidemiological , c l in ical , or forensic detai lsbeyond a mention that a death or event had occurred. Asimple assessment of study quality was conducted witharticles rated at low, moderate, or high risk of bias byone of the authors (AH; cr i ter ia avai lable on request).

Results

Twenty-three original studies on the health effects ofgaseous emissions in volcanic areas and six papersrelating to a historical review were located (Table 1).

These could be broadly grouped into impacts of mod-erate or large-scale eruptions,20 26 investigations ofunexplained mortality,2T-33 and long-term effects ofexposures from degassing or numerous eruptions.3447

Study methodology. Nineteen of the studies were epi-dem i o I og i ca I t20'21'27'28'31'3

447 11111 6 were fo re n s i c,2e'30 two

were case-reoorts32,33 and six concerned a search ofprimary h istorical I i1s131u ps.8,22-26

Study quality. All of the studies were rated at high ormoderate r isk of bias (Table 1), mainly because of inad-equacies in exposure assessments and study designs.Most study designs were lower on a conventional hier-archy of evidence as used in systematic review andmeta-analysis.as The methods of two studies wereunclear,4l ,42 so they were not considered further.

Eleven of the studies did not have actual exposuremeasures bu t used prox ies such as l i v ing nearsource,20,21,34,36-39,4446 exposure zones covering placeof residence,37,3e or wind direction.a0 Three of thesestudies36-38 also measured or reported ambient exposure

629

Baxterl gBg2B

K l i ng198730

Wagner.l

9BB2e

Ze 199627

Le Cuern199231

H i l l200032

Bates'l99746

Bates19984s

Bates200247

Kage.l gg833

Legator200144

Shinkura1ggg3s

Tomari1 99036

Uda199934

Lake Nyos disaster, Cameroon,I986: the medical effects of largescale emission of carbon dioxide?

The .l 986 Lake Nyos gas disaster inCameroon, West Africa

Medical evaluation of the vict ims ofthe 'l 986 Lake Nyos disaster

Respiratory symptoms and peakexpiratory flow in survivors ofthe Nyos disaster

An example of health hazard:people ki l led by gas during aphreatic eruption: Didng PlateauUava, Indonesia), February 20th1979

Possible asphyxiation from carbondioxide of a cross-country skierin eastern Cali fornia: a deadlyvolcanic hazard

Air pol lut ion and mortal i ty in theRotorua geothermal area

Cancer incidence, morbidity andgeothermal air pol lut ion inRotorua, New Zealand

Investigation of health effects ofhydrogen sulfide from ageothermal source

A fatal case of hydrogen sulfidepoisoning in a geothermal powerplant

Health effects from chroniclow-level exposure to hydrogensu lfide

Relationsh ip between ambientsulfur dioxide levels and neonatalmortal i ty near the Mt Sakuraj imavolcano in Japan

Comparison study on pulmonaryfunction in school chi ldren-effect of volcanic activity fromMt Sakura j ima and a lh le t i ccapabil i ty on the health ofschool chi ldren

Asthma-l ike disease in the chi ldrenl iving in the neighborhood ofMt Sakuraj ima

Lake Nyos,Cameroon

Lake Nyos,Cameroon

Lake Nyos,Cameroon

Lake Nyos,Cameroon

Sini la volcano,Dieng Plateau,)ava,Indonesia

MammothMountainarea, California

Rotorua,New Zealand

Rotorua,New Zealand

Rotorua,New Zealand

lapan

Puna, Hawai i

cross-sectionalsurvey ofcohort ofsurvivors

descriptive

case reporr

ecological

ecological

ecological

case repon

cross-sectionalsurvey

ecological

cross-sectionalsurvey

cross-sectionalsurvey

CO,

CO,

CO,

Cot

il-)High-remote area with no medical

faci l i t ies so exposure, cl inical,and forensic assessments wereconducted weeks to months afterthe event

High----only 257" of survivors werestudied. Actual exposures levelsunknown. Potential ly sensit ive(chi ldren, elderly, preexist ingrespiratory disease) excluded.

High-Remote area. Exposureassess-ments conducted 5 moafter event. No forensic orcl inical assessments.

H igh----exposure assessments carriedout 2 days after the death,forensic evidence not conclusivethat CO2 caused death

High-no exposure measures, con-founding from ethnicmisclassification on deatncert i f icates lMaoris have higherexposures)

High-no exposure measures, smallnumber of cases

Moderate-exposures based onplace of residence, informationon confounders limited togender, age, and ethnicity

Moderate-exposu re assessmentscarried out 1 wk after the death

H igh-response bias (communitybelief that the geothermal plantinvolved was making them sick),exposure measures not availabledue to local pol i t ics

High-number and location ofmonitoring stat ions not given.Not al l SO, in the city wasderived from the volcano.Potential incompletecapture of neonatal deaths.

Moderate--difficult to assess ful lyas only abstract and tables inEnglish. Number and location ofmonitoring stat ions not given.

Moderate-number and location ofmonitoring stat ions not given.Response bias possible with self-assessment questionnaire onsymptoms.

Coz

Coz

H,S

H:S

H,S

H,S

H,S

Mt Sakuraj ima,Japan

Mt Sakuraj ima,Japan

Mt Sakuraj ima,Japan

SO,,volcanicasn

Sor,particulates,NO,

SO,,volcanicash,particulates

Table 1.-Studies Relating to Health Effects of Volcanic Cases: Agent Studied, Location, and Risk of Bias

Volcano/ Agent(s)Region ldentified Type of StudyArticle Tit le

Assessment of Risk ofB ias-Reason

(Continues\

630 Archives of Environmental Health

Table l.-studies Relating to Health Effects of Volcanic Cases: Agent Studied, Location, and Risk ol Bias (Continued)

Art icle Tir leVolcano/ Agent(s)Region ldentified Type of StudY

Assessment of Risk ofBias-Reason

Wakisaka'l 98837

Stephenson1 gg l 38

Mann ino1gg63e

Chen1ggg40

5mrtn1 9984r

Smith199942

Michaud200443

Leus1 981 20

Witham200321

Crattan2O03a23

Crattan2003b24

Crattan1998a26

Crattan1 998b2s

Durand1ggg22

Durand2001 8

Effects of volcanic activity on themortality figures for respiratorydisease

Exposure to volcanic emissionsfrom the Hawai ian volcanoes: aNIOSH heal th hazard evaluat ion

Emergency department visits andhospital izations for respiratorydisease on the is land of Hawai i ,1 9 8 1 t o ' l 9 9 1

Study on the effect of wind directionon emergency room visits forasthma among chi ldren in Hi lo,Hawai i is land

The effects of "vog" on therespiratory systems of Hawai iPreparatory Academy Students

The human heal th response to'rog"

Emergency department visits and"vog"-re lated ai r qual i ty in Hi lo.Hawai i

Asthmatic bronchitis associatedw i t h a vo l can i c e ruP t i on i nSt. Vincent, West Indies

Mortal i ty in England dur ing the1783-4 Laki Craters eruption

Human sickness and morta l i ty ratesin re lat ion to the distant erupt ionof volcanic gases: rural Englandand the 1 783 erupt ion of theLaki f issure, lceland

l l lness and elevated humanmortal ity coi ncident withvolcanic erupt ions

Model l ing the impacts of pastvolcanic gas emissions: Evidenceof Europe-wide environmentalimpacts from gases emitted inI ta l ian and lcelandic volcanoesin 1783

The environmental tox icology ofvolcanic gases in the EuroPeanenvtronment

Extensive respiratory health effectsof volcanogenic dry fog in 1793inferred from Europeandocumentary sources

Effects of volcanic a i r pol lut ion onheal th

SOr, ecologicalpart iculates

High-difficult to assess as onlyabstract and tables in English.Concentr ic circles used asexposure measures. Noinformation on confounders suchas smoking.

Moderate-S0o/o response rate.Exposures measured on a daywith low emissions.

High-exposure zones based onconsensus of two cl inicians whotreated patrents

High

Methods unclear

Methods unclear

Moderate-two ambient Pol I utionmonitors used, so ecologicalfal lacy may apply. Noinformation on confounders

High-no exposure assessmentsavai lable

High-potential bias in Parishmortality records (the mortalitYdata source), only deaths ofChurch of England membersrecorded, no exposure measures.

High-review of historicaleyewitness reports

H igh-review of h istoricaleyewitness report and descriptiveanalyses of dataset used byWitham 2003 (qv)

H igh-review of historicaleyewitness reports

Mt Sakuraj ima,

Japan

Hawai iVolcanoesNat ional Park,Hawa i i

Hawai i

Hawa i i

Hawa i i

Hawai i

Hawa i i

Soufrierevotcano/St. Vincent ,Windwardls lands

Laki f issure,lceland

Laki f issure,lceland

Laki f issure,lceland

Laki f issure,lcelandEtna, Volcano,Strombol i ,I ta ly

Laki f issure,lceland

Laki f issure,lceland

Laki f issure,lceland

so2, HCI

"vog," So2acidaerosol

"vog": So2 ,particulates

"vog"'.particulates

"vog":particulates

"vog": so2,particulates

acidaerosols/volcanicash

acid aerosols

cross-sectionalsurvey ofparKemproyees

ecological

ecological

ecological

ecological

ecological

descriptive

ecological

acid aerosols

acid aerosols

acid aerosols

histor icalreview

histor icalreviewdescriptive

histor icalreview

acid aerosols

acid aerosols

acid aerosols

historicalreview

historicalreview

h istoricalreview

High-review of historicaleyewitness reports

High-review of h istor icaleyewitness reports

H igh-review of historicaleyewitness reports

December 2004 [Vol. 59 (No. 12)]

measures but did not formal lv l ink them to the healthdata.

Even where exposure measurements were used in theanalyses, potent ial for bias remained. Smal l numbers ofambient air qual i ty monitor ing stat ions were used insome studies,3s,a3 which may not ref lect individualexposures. ln urban areas i t was unclear how much ofthe SO, measured could be attributed to volcanicsources.3s lt was not always possible to make measure-ments close in time to the actual health outcome.2T-31Individual exposure measures were attemoted in onestudy,38 but were conducted on a single day.

Health hazards from volcanic gases. Due to the smallnumbers of studies and high r isk of bias, a formal r iskcharacterization of health hazards from volcanic gases,including dose-response relat ionship was not possible.However, the publ ished studies did al low a oual i tat ivedescript ion of the types of hazards encountered.Addit ional qual i tat ive information was avai lable fromreports of health effects from various sources (Table 2).

Carbon dioxide. CO, is given off in large quantitiesduring volcanic erupt ions and in volcanical ly act iveareas. Exposures generally occur from CO, clouds orfrom CO2 accumulat ions in low-lying areas (as CO, isdenser than air) . CO2 accumulat ions in volcanical lyactive areas may be difficult to detect, because the gasis odorless and accumulations may occur intermittently.TConcentrat ions of 10 and 30% oroduce unconscious-ness in about 10 min and 1 min, respect ively, and mayresult in seizures followed by death.ae Such effects maybe seen at lower concentrations (> 5%) if exposure isprolonged.T

The best-studied event related to 1,700 deaths atNyos (volcanic) crater lake in Cameroon in 1986.Epidemiological2B and forensic2e,30 studies suggestedthat a CO2 cloud was responsible. The favored explana-tion for the origin of the cloud was that large quantitiesof CO, had been discharged into the lake, resulting inhigh concentrat ions held in solut ion under pressure andan event such as a landslide had triggered a catastroph-ic release. Due to the remoteness of the area, formalinvestigations were conducted weeks to months afterthe event. A similar situation had occurred at LakeMonoun, about 100 km south of Lake Nyos in 1984,when 37 people were ki l led by a cloud of gas alsothought to be CO2.s0 lnvestigations in the Lake Monounevent took place 6 mo afterward; no autopsies were per-formed, and no t issue samples were avai lable. A thirdCO, cloud event was associated with a minor phreaticerupt ion at Sini la volcano, Dieng Plateau, Indonesia, in1979, which led to 139 deaths.31 Deaths from accumu-lations of CO, were fully documented in only one study,a case report of the death of a skier in the MammothMountain area in Cal i fornia.3l

The chief documented human health effect of CO2 inprimary studies was asphyxiation from exposure to high

632

concentrations. A kev feature of these events was thatthose affected were described as looking as if they hadfallen asleep where they stood, suggesting very little orno warning of the hazard.ae The only avai lable warningsof potential danger appeared to be dead animals orbirds, generally seen in caves or depressions in theground,ae,so or tree-kill.32 Reports of COr-related deathswere found for many other volcanic areasae (Table 2)including southern l Ialy,s,7 Japan,sl and Nicaraguas2 andare suggested in the folk lore of volcanic areas includingHawai is3 and Cameroon.ae

Bul lous and erythematous skin lesions resemblingburns chief ly on the face (especial ly cheeks), legs,abdomen, and back were reported in humans ki l led inthe Lake Nyos event,28 but such skin lesions were notseen in cattle, nor were they a feature in the Diengevent.ae Bl isters and blackened skin simi lar to burnswere key features of eyewitness reports of a CO2asphyxiat ion near Cosigt l ina volcano, Nicaragua, inves-tigated by one of the authors (AH) (Table 2), but werenot reported in the Mammoth mountain death.32 Precisedetai ls about exposures were not avai lable in any ofthese studies, so i t is unclear whether "burn" lesionsrelate to the concentration and duration of CO, expo-sures or to the presence of other gases. A smell of rotteneggs and gunpowder, possibly indicat ing hydrogen sul-fide or SO2 was reported by some Lake Nyos disastersurvivors, but could not be substantiated by the limitedforensic examinations and may have been due to olfac-tory hal lucinat ions induced by CO2.30 The Nyos l i tera-ture ascribed apparent "burns" to dependent changesrelated to the comatose state of those exoosed.28,30

Only one study invest igat ing long-term sequelae hasbeen conducted.2T The authors found no evidence ofrespiratory symptoms or reduced peak expiratory flowin approximately a quarter of Lake Nyos survivors 4 1/2 yrafter the event. However, those potent ial ly mostsusceptible-the elderly, children, and those with pre-existing respiratory disease-were excluded from thestudy. Long-term effects, particularly on nonregeneratingtissue such as the brain and nervous systemf were notinvestigated, but Baxter2s commented on the absence ofgross neurological or psychological sequelae in sur-vivors 2 wk and 1 yr after the event.

Sulfur dioxide. SO2 is a common component of vol-canic emissions and is less quickly removed from theplume than other acidic gases such as HCI and HF. TheWorld Health Organizat ion air qual i ty guidel ines forEurope set maxima for SO2 exposures at 500 p,{m3 llZSppb) over 10 min and 125 p"glm3 (44 ppb) for dai lyaverages.sa Predominant short-term effects are irritationof the eyes and respiratory tract and airway constrictionin asthmatics, but these effects are unlikely below200-500 ppb.ss

Four Japanese studies relating to SO, exposures fromongoing minor eruptions of Mt. Sakurajima, and volcanic

Archives of Environmental Health

Table 2.-Reports of Deaths and Adverse Health Effects in Active Volcanic Areas Attributed to Volcanic Emissions

Place Date Event Agent Source of lnformation and Comments

Laz io and A lban H i l l s(near Rome), l taly

Furnas, Sdo Miguel,Azores

Near Cosigi i ina volcano,N icaragua

Hakkoda, NE Japan

Sikidang crater, DiengPlateau, Java

Vulcano is land, l ta ly

Aso Volcano, Kyushu,Japan

Hawai i VolcanoesNat ional Park, US

Adatara Volcano,NE Japan

Rotorua, New Zealand

Mount Nyiragongo,Democratic Republicof Congo

.l death; man fel l intoabandoned well

"At least ' l 0" deaths " l inkedto" elevated CO,

Workers in trenchesovercome by gasaccumulation; no deaths

2 deaths of youths digginga we l l

1 death of a man digginga we l l

3 deaths of soldiers on at ra in ing miss ion

1 death and 2 hospital izat ionsfrom a sudden gas emission

2000

1 983-2003

1999

Mar 19981992

)uly 1997

Mar 1992

1 9BOs

Nov 1997June

' l 99419BO-97

19871 983-2003

CO, Death of man in 2000 mentioned bv Beaubien.TAnnunziatel l is,sr and Carapezzasl together withdeaths of cows and sheep in the area. Addit ionaldeaths 1983-2003 mentioned in BeaubienT butno detai ls given.

Furnas is located in the caldera of an activevolcano. Baxter et al.6 mapped substantial soi lgas emissions of CO, and Rn. Animal but nohuman deaths from CO2 were reported.

Personal visi t by one of the authors (AH) and localnewspaper report.s2 Concentrations ol 7.2"/" CO2and 10.0% O, in the well 2 days after 1998deaths.

Volcano Research Centre of japan{ http : / /hakone.eri .u{okyo.ac.jp, accessed8 February 2006) and later paper by Perez et al.srCO2 concentration 1 5-20% at scene

Previously on Clobal Volcanism program. Web siteat www.volcano.si.ed u/gvp/wo rld/ r egion06/javald ieng/var. htm#sean_0402but on 3' l March 2005 only avai lable athttp ://users.bend net.com/bjensen/volcano/indonesia/ java-d ieng.htm l.

Surface gas measurement the following day of CO2at 40"/o and 02 at 15o/o. Other gases detectedinc luded H2S 200 ppm and HCN 197 ppm.

Mentioned in Baubron 1990.s "Deaths fromasohvxia" in Vulcano also mentioned in Baxter1ggg.85

CO,

Coz

CO,

CO,

Sept 1 997

19461948

1954

19541954

1962

1962

1987

lan 2002

2 chi ldren at Vincenzino well CO,

2 deaths of tourists SO: Volcano Research Centre of Japan5 deaths of chi ldren on (http//hakone.eri .utokyo.ac.jp, accessed 31 March

school excursion 2005)7.1 hospital izat ions due

ro gases1 death of tourist with asthma SO, 1987 death mentioned in Stephenson 199.1 384 deaths in the last 20 yr gases 1 983-2003 deaths reported in conversation with

park ranger by one of the authors (AH). The parkcareful ly monitors volcanic activi ty and placesdangerous areas off- l imits. Al l four deaths

4 deaths or hikers in crater HzS ".i.'"'"T'F:#I:18#:;?H:X iil,ifr"ffi::

floor eri.u-tokyo.ac.jp, accessed 8 February 2006). HrSconcentration 400 ppm at 1 m above ground

1 death in public spa pool \ The New Zealand Herald newspapers6 with source2 affected by gases in sewer I credited to Dr. Michael Durand, Canterbury

pipe,. l death I University.5 affected by gases in septic I

tank, 1 death I Further information obtained direct ly from Ross1 death in hot pool I Price and Phil Shoemack of Toi Te Ora public1 death of man digging sump \HrS health department covering Rotorua:

hole ) confirmation of the deaths in 1954 and 19872 deaths; groundwater heating f and reports of a further possible three deaths

system leaks I from HrS related to spa pools in 2000 (1 death). l death; bui lding I and 2003 (2 deaths).accumula t ion o f gas I

2 deaths; faulty shower trap Ig iv inB connect ion w i th Igroundwater heating system /

1 death when lava flow Unknown British newspaper reportsT cites "toxicreached city of Coma fumes," but these may have resulted from lava

burning asphalt roads3s rather than direct lyrelated to volcanic sases

December 2004 [Vol. 59 (No. 12)] 633

ashfalls were located. Annual averages of daily meanvalues of SO2 in Sakurajima town were reported as rang-ing between 44 and 158 ppb in 1979-85,37 2Og ppb in1988,36 and 31 ppb in 1992.34 No effect was seen onself-reported prevalence of respiratory disease, respira-tory symptoms34,36 or on lung function of schoolchild-ren36 living in Sakurajima town compared with those atschools in control areas. Higher standardized mortalityratios for bronchitis and oneumonia were seen withplace of residence closer to the volcano,3T but the rela-t ionship was not conclusive for asthma or emphysema.Positive correlations with annual mean SO2 and totalsuspended particulate levels were seen for bronchitisdeaths but inverse correlations were seen for pneumo-nia deaths. Neonatal mortal i ty in Kagoshima ci ty ( fur-ther from the volcano than Sakurajima town) wasrelated to SO, levels,3s but it was unclear how much ofthe SO, was derived from volcanic sources, becauselevels were not markedly different from those seen inother Japanese cities.

Park rangers in the Hawaii Volcanoes National Parkare intermittently exposed to high levels of volcanicgases, chief ly SO, and HCl, in the course of their dai lywork. An occupational exposure study,38 in whichapproximately half (a3) of park employees returnedquestionnaires, found that "more than half" reportedsymptoms including headaches, eye irritation, throatirritation, cough, and phlegm as well as chest tightnessor wheezing and shortness of breath. Ambient SO2 con-centrations exceeded U.S. occupational limits at sever-al s i tes of high exposure (0.8 and 1 .7 ppm along a trai l ,5.0 ppm in a car park, 4.1 ppm at a vent source, and 1 .2ppm about 1 m from a volcanic vent), but personalexposure measures showed no detectable SO2.

There were reports of a small number of deaths inJapan and Hawaii-usually of asthmatic tourists-relat-ed to high levels of SO2 from degassing episodes, butfew details were available (Table 2).

Acid aerosols. Acid aerosol clouds may be associatedwith eruptions or with degassing events in volcanicareas. Several components of plumes are acidic, includ-ing SO2, HCl, and HF. H2S is abundant in some emis-sions and oxidizes in the atmosphere to SO2. Furtheratmospheric oxidat ion of SO2 yields clouds containinghigh concentrations of submicron sulfate particulates.Very low pH sulfate aerosol also appears to be releaseddirectly from some volcanic vents.s6,57 Acid aerosolclouds may affect large areas and were generally report-ed to cause respiratory effects and irritate the eyes.There are exposure limits for particles but not for acidaerosols; the U.K. air qual i ty standard for PM,o part ic lesis 50 pglm3 for a 24-hr rolling average.s8

The erupt ion of Laki in lceland in June 17834 result-ed in an acid gas and aerosol "fog" visible for days toweeksse affecting many parts of Europe. Concentrationsof SO, in the cloud may have been quite high and

634

deposited as SO, pr ior to oxidat ion to sul fate.60Numerous contemporary documents report respiratoryand eye symptoms.B,22,23 Analyses2r of U.K. parish mor-tality records representing approximately 7'h of the pop-ulation at that time suggested an average increase inmortality of 4O'h during August and September com-pared with the average for the surrounding 50 yr, withhigher impacts suggested for parishes in East Anglia,which might be expected to have had the highest expo-sures. However, it is unclear whether the increased mor-tality was directly related to the acid aerosol "fog,"caused indirectly through effects on crop yields, or dueto unusual ly high summer temperatures and a feveroutbreak.

Acid aerosols composed of SO2, sulfur trioxide, andhydrogen sulfide were held to be responsible for anincrease in pediatr ic admissions with "asthmatic bron-chit is" fol lowing a 1979 erupt ion of the Soufr idre vol-cano in St. Vincent, Windward ls lands,2o but exposureswere not reported and effects may have resulted fromconcomitant volcanic ash exposure.

Three ecological studies3e,40,43 examined the healthimpacts of "vog," a mist of SO2 and sulfate particlesemitted from Ki lauea, Hawai i . Emissions are substant ialwith estimated emissions of 1,000 Mg/d (i.e., tonnes/day)SOsince 198643 and of the order of 50 Mg/d of sul fateaerosol 10 km from source.61 The f i rst examinat ion byMannino et al.3e suggested increased hospitalizationsand emergency room visits for asthma and chronicobstructive pulmonary disease (COPD) in zones withhigher volcanic gas exposures. The f indings for emer-gency room visits for childhood asthma were replicatedin a reanalysis of these data by Chenao using wind direc-tion from Kilauea as the exposure measure. A moresophisticated analysis using actual exposure measuresand time series methodology found increases in asthmaand COPD emergency room visits ol 6.8"h per 10 ppbincrease in SO2 with a 3-d lag and 13.8% per 10 pglm3PM, (submicron aerosol, chief ly sul fur ic acid) with a1-d lag.a3 These impacts were lower than suggested bylocal perceptions, but exposure measurements revealedthat days of high "vog" exposures were rare.

Hydrogen sulfide. HrS is chiefly encountered in areaswith high geothermal activity and occupational settings.Acute exposures to accumulations of > 700 to 1000ppm cause unconsciousness within minutes fol lowed bydeath from HrS poisoning.7,62 Such effects have beenreported in geothermal power plants,33 in accumula-t ions in conf ined spaces in volcanic and geothermal lyactive areas,aT and accumulations related to geothermalheating systems (Table 2).

Pooulation health effects of chronic low-level exoo-sures have been little studied, and most guidelines aredesigned to protect against symptoms during occupa-t ional exposures of working adults. The U.S. Agencyfor Toxic Substances and Disease Registry (ATSDR)

Archives of Environmental Health

minimum risk levels, set to be below those that mightcause adverse health effects in the most sensitive indi-viduals in a populat ion, are 70 ppb for acute (1-14 d)and 30 ppb for intermediate (15-364 d) inhalationexposure to H25.63 These were based on a study show-ing respiratory effects in 2 of 10 individuals and on astudy in mice, respectively.6a

Three ecological studies of the health effects of chron-ic exposures to H2S were conducted by Bates et al.4s47in Rotorua, New Zealand, which has one of the largestpopulations Iiving over an active geothermal field. Thefirst two studies suggested higher respiratory mortality46and respiratory cancer risksas in Maori women andincreased hosoital admissions for nervous system dis-eases in Rotorua residentsa5 compared with NewZealand averages. The third study incorporated expo-sure measures dividing the city into low, medium, andhigh H2S exposures. Dose-response trends were seen forhospitalizations for diseases of the nervous system withan approximate doubl ing of r isk of admission forperipheral nervous system and sense organ disorders forhigh as opposed to low exposure level areas. The actualH2S levels approximated to = 1 ppm in high areas and< 50 ppb in low areas averaged over a 7-d period.6sWeaker trends were seen in hospitalizations for circula-tory system and respiratory system disorders.Adjustments were made for age, gender, and ethnicitybut not for other important confounders such as socioe-conomic circumstances and smoking.

A surveyaa of pooled symptom reports of residents inPuna, Hawai i , l iv ing within B km of a geothermal plantand Odessa, an American community with an industrialsource of H2S, found relative risks were higher in theexoosed communit ies than in control communit ies forall body symptoms. Relative risks for central nervoussystem and respiratory symptoms were at least twice ashigh as those for other systems, consistent with theRotorua findings, although at presumed lower expo-sures. However, findings may reflect response bias,given acknowledged political controversy related to H2Sexposure in both Puna and Odessa. Although actual H2Smeasurements in Puna were not made available to theresearchers, a report by the ATSDR66 suggested hourlyaverage values in the low ppb range, with occasional(on average fortnightly) peaks, usually < 50 ppb.

Discussion

Volcanic emissions have been studied in somedetail,l+,02,04 and the potential for health effects is wellrecognized.a,6s-70 However, surprisingly few primarystudies on the health effects of volcanic air pollution havebeen conducted. lt would be unwise to assume that lackof publications reflects lack of hazard. Hazards may notbe fully appreciated, particularly if these result in smallincreases in risks spread across a large population or to

December 2004 IVol. 59 (No. 12)l

intermittent sporadic events. Some of the affected areasare remote or in poor countries, with inadequate localhealth data. In some cases health studies may not be wel-comed,44 for example, if tourism is an important source ofrevenue. Additionally, the perception of risk from a natu-rally occurring form of pollution may be lower than theperception of risk from a man-made source.

Most of the studies identified had inadequate expo-sure measures and used study designs with high risk ofbias. Although they provide descriptive information thatcould be used to generate hypotheses for future studies,it was impossible to assess whether findings in thesestudies were consistent with studies of anthropogenic airpollution or occupational exposures. Only one study, byMichaud,a3 relat ing to emissions from Ki lauea onHawaii, provided information on dose-response rela-tionships. Coefficients for the relationship between vol-canic SO2 emisions and emergency room visits werevery similar in magnitude and timing to those reportedfrom anthropogenic sources.Tl ,72 However, it was notpossible to compare coefficients for sulfate acid aerosol,because no studies of anthropogenic SO2

"ffs61573-75used an equivalent submicron measure for acidaerosols. Descriptive findings from studies of long-term,low-level ambient H2S exposures4447 were consistentwith findings of nervous system effects in occupationalstudies,T6 but additionally suggested effects on the respi-ratory and circulatory systems.

Methodology used for the literature search. In com-mon with other authors,45,67,77,78 this search identifiedrelatively few studies, despite the use of text wordsearches to maximilze sensitivity and attempts to identifypapers through col leagues and the Internet. Somestudies may have been missed: for example, those with-out at least an abstract in Engl ish or in journals notincluded in the databases searched. Because of thesmall number and heterogeneous nature of the articlesand the fact that some studies were carried out underdi f f icul t c ircumstances, a del iberately simple assessmentof qual i ty was used.

Recommendations for future studies of volcanicgases. All health studies should attempt to obtain goodexposure assessments, preferably through collabora-tions with geochemists, so that dose-response effectscan be quant i f ied. Exposure assessments ideal ly shouldbe conducted near the individual and close to the timeof the health event with the percentage of gas or aerosolattri butable to volcan ic sou rces esti mated. Add itiona I lv,researchers should consider interactions between vol-canic and ambient (anthropogenic) air pol lut ion anddetails of gas chemistry.

Epidemiological studies are lacking for several volca-noes producing large quantities of gases in proximity topopulated areas, such as Mount Etna on Sici ly,Popocat6petl near Mexico City, Miyakejima in Japan,Nyiragongo in the Democratic Republic of Congo

Fig. 1. Mount Nyiaragongo looming over Goma, DRC. Mount Nyiaragongo is presently likely to bethe largest point source of sulfur and halogens on earth. 6oma has a population of approximately500,000, Photo reproduced by permission of Simon Carn,

(Fig.. l ) , and Masaya in Nicaragua. For example, SO,emissions from degassing at Masaya indicate that popu-lations directly downwind may be regularly exposed tolevels of up to 1 ppm,67 with daily averages estimatedat > 75 ppbv.68

Volcano tourism is becoming increasingly popular inmost areas of the world. The risks for the tourist are notwel l character ized, and volcanic airborne chemicalhazards are potentially a greater threat than direct phys-ical hazards. Deaths from volcanic gases occurr ing assporadic events (see Table 2) seldom reach the peer-reviewed l i terature. Signif icant exposures result ing inmedical attention but not death are even less likely to bereported. Volcano observatories could play an impor-tant role in collecting information on fatal and nonfatalevents related to tourism and other exDosures.

In cases of skin changes associated with high CO2exposures, histopathological examination of the skinand biochemical analyses of the bul lae f lu id are neededto help determine the cause of blisters and the appear-ance of burns on the skin.28,30 Further studies are arsoneeded to assess any long-term neurological and psy-chological effects in survivors of high CO, exposures.

No publ ished papers were located determining thehuman health effects of halogen gases HF or HCI-either as LAZETe (a dense hydrochloric acid mist formedwhen lava enters sea-water on Kilauea) or as a primaryemission. Fluorosis has been associated with volcanic

636

areas8o,Bl but has been studied in relation to volcanicash and not to HF gas. Radon emissions may lead to lev-els causing concern in areas with ongoing degassing6,B2and active geothermal areas,B3 but cancer risks in theseareas have not been investigated.

Volcanic air oollution deserves further medical atten-t ion. Volcanic emissions may produce air pol lut ionepisodes (e.9., Laki) or contribute to urban air pollution(e.g., Popocat6petl volcano near to Mexico City) and havethe potential to affect large communities. Although volca-nologists have produced detailed studies characterizinggaseous emissions of volcanoes, and epidemiologists havedone extensive research on health effects of anthropogenicair pol lut ion, their work has seldom overlapped.Collaboration between these two groups is neededbecause of potential for widespread exposures to volcanicgases and the relative lack of information about the poten-tial risks. Such research may also be helpful to improvecharacterization of risks from anthropogenic sources. Allresearchers need to be aware of local concerns.Community engagement and approval is important andshould be sought at the planning stages of health studies.

* * * * * * * * * *

The authors thank Claire Horwell, the International VolcanicHealth Hazard Network (www.ivhhn.org); Ross Price and PhilShoemack of Toi Te Ora public health department, NewZealancl; and Simon Carn.

Archives of Environmental Health

Submitted for publication December 15,2004; accepted forpublication February 1 6, 2005.

Requests for reprints should be sent to Dr. Anna Hansell,Dept Epidemiology & Publ ic Heal th, lmper ia l Col lege London,Norfo lk Place, London W2 1PC, UK.

E-mai l : a .hansel l@imper ia l .ac.ukCopyright O 2006 Heldref Publications

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