1196 VOLUME 113 | NUMBER 9 | September 2005 • Environmental Health Perspectives

Research

The life expectancy in Bangladesh during themid-1960s was only 46 years. Many pre-mature deaths resulted from drinking surfacewater that was contaminated with bacteriacausing diarrhea, cholera, typhoid, and otherlife-threatening diseases (Nyrop et al. 1975).Aid agencies, the Bangladesh government, andprivate individuals began installing 8–12 mil-lion tube wells to prevent these deaths by pro-viding access to microbially safe groundwaterfor drinking [World Health Organization(WHO) 2003]. By 1995, Bangladesh had120 million people (Monan 1995), approxi-mately 97% of whom drank tube-well water(WHO 2000), and for a variety of reasons thelife expectancy had increased to 55 years(Monan 1995).

Regrettably, this new source of drinkingwater was not tested for toxic metals. In1993, Dhaka Community Hospital first diag-nosed chronic arsenic poisoning caused bydrinking Bangladesh’s groundwater [BritishGeological Survey (BGS) 1999a]. In 1997,our team produced the first national-scale mapof As concentration in Bangladesh’s ground-water [Frisbie et al. 1999; U.S. Agency forInternational Development (USAID) 1997].This map showed that 45% of Bangladesh’s

area had groundwater with As concentrationsgreater than the 50 µg/L national standard(Frisbie et al. 1999; USAID 1997). In 2003,a risk assessment estimated that 28 millionBangladeshis were drinking water with Asconcentrations greater than this national stan-dard (Yu et al. 2003). As a result of this expo-sure, skin cancer, melanosis, leukomelanosis,keratosis, hyperkeratosis, and nonpittingedema from chronic As poisoning are com-mon in Bangladesh (BGS 1999b; Frisbieet al. 2002). In addition, the rates of bladdercancer, liver cancer, and lung cancer areexpected to increase in Bangladesh based onan analysis of death certificates for As expo-sures in Taiwan (Morales et al. 2000).

Fortunately, our 1997 study (Frisbie et al.1999; USAID 1997) also suggested that test-ing and sharing tube wells could rapidly andinexpensively provide drinking water with Asconcentrations less than the 50 µg/L nationalstandard to 85% of Bangladesh’s population.That is, 85% of Bangladesh’s neighborhoodshave at least one tube well that does notrequire treatment for As removal beforedrinking. Therefore, the vast majority ofBangladeshis with unsafe water could poten-tially get safe drinking water from their

neighbors (Frisbie et al. 1999; USAID 1997).As a result of this discovery, groundwater test-ing has become a major component of anoverall strategy for providing safe drinkingwater to the people of Bangladesh. To date,> 1 million of Bangladesh’s approximately10 million tube wells have been tested for Aswith easy-to-use, relatively inexpensive, andsemiquantitative field kits [UNICEF (UnitedNations Children’s Fund) 2004]. Tube wellsare considered safe and marked with greenpaint if the As concentration is ≤ 50 µg/L, thenational standard. Conversely, tube wells areconsidered unsafe and marked with red paintif the As concentration is > 50 µg/L. Thosewith safe water are asked to share with theirless fortunate neighbors. In addition to thisinitial survey, periodic testing of tube wells hasbeen recommended to ensure that the popula-tion has continued access to safe drinkingwater. This periodic testing is prudent becausethe As concentration in some of Bangladesh’stube wells has changed dramatically over time(Frisbie et al. 1999; USAID 1997).

This urgent need to periodically testapproximately 10 million tube wells and thelimited resources of Bangladesh have led to theuse of these semiquantitative field kits formeasuring As. However, these field kits are notprecise because the user must estimate the con-centration of As from a color chart, similar tothat used for measuring pH with pH paper.There are two commonly used field kits inBangladesh. The first kit is not sensitive and

Address correspondence to B. Sarkar, Department ofStructural Biology and Biochemistry, Hospital forSick Children, Department of Biochemistry,University of Toronto, 555 University Ave., Toronto,Ontario M5G 1X8, Canada. Telephone: (416) 813-5921. Fax: (416) 813-5379. E-mail bsarkar@sickkids.on.ca

We thank K. Adam, M. Quader, and M.A.El Shakankiri.

This study was supported by Better Life Labora-tories, the Bangladesh Association for Needy PeoplesImprovement, Green Mountain Laboratories,CNRS (Centre national de la recherche scientifique)at the Université de Bordeaux 1, the Hospital forSick Children, SETU (Services for Education,Training and Unity), and L. Spence.

The authors declare they have no competing financialinterests.

Received 28 January 2005; accepted 19 May 2005.

The Development and Use of an Innovative Laboratory Method forMeasuring Arsenic in Drinking Water from Western Bangladesh

Seth H. Frisbie,1 Erika J. Mitchell,1 Ahmad Zaki Yusuf,2 Mohammad Yusuf Siddiq,2 Raul E. Sanchez,3

Richard Ortega,4 Donald M. Maynard,5 and Bibudhendra Sarkar 6,7

1Better Life Laboratories, Inc., East Calais, Vermont, USA; 2Bangladesh Association for Needy Peoples Improvement, Chorhash, Kushtia,Bangladesh; 3Green Mountain Laboratories, Inc., Montpelier, Vermont, USA; 4Laboratoire de Chimie Nucléaire Analytique etBioenvironnementale, Université de Bordeaux, Gradignan, France; 5Johnson Company, Inc., Montpelier, Vermont, USA; 6Department ofStructural Biology and Biochemistry, Hospital for Sick Children, and 7Department of Biochemistry, University of Toronto, Toronto,Ontario, Canada

All of Bangladesh’s approximately 10 million drinking-water tube wells must be periodically testedfor arsenic. The magnitude of this task and the limited resources of Bangladesh have led to the use oflow-cost, semiquantitative field kits that measure As to a relatively high 50 µg/L national drinkingwater standard. However, there is an urgent need to supplement and ultimately replace these fieldkits with an inexpensive laboratory method that can measure As to the more protective 10 µg/LWorld Health Organization (WHO) health-based drinking water guideline. Unfortunately,Bangladesh has limited access to atomic absorption spectrometers or other expensive instrumentsthat can measure As to the WHO guideline of 10 µg/L. In response to this need, an inexpensive andhighly sensitive laboratory method for measuring As has been developed. This new method is theonly accurate, precise, and safe way to quantify As < 10 µg/L without expensive or highly specializedlaboratory equipment. In this method, As is removed from the sample by reduction to arsine gas,collected in an absorber by oxidation to arsenic acid, colorized by a sequential reaction toarsenomolybdate, and quantified by spectrophotometry. We compared this method with the silverdiethyldithiocarbamate [AgSCSN(CH2CH3)2] and graphite furnace atomic absorption spectroscopy(GFAAS) methods for measuring As. Our method is more accurate, precise, and environmentallysafe than the AgSCSN(CH2CH3)2 method, and it is more accurate and affordable than GFAAS.Finally, this study suggests that Bangladeshis will readily share drinking water with their neighborsto meet the more protective WHO guideline for As of 10 µg/L. Key words: arsenic, arsenomolybdate,Bangladesh, chronic arsenic poisoning, drinking water, graphite furnace atomic absorption spec-troscopy, silver diethyldithiocarbamate, spectrophotometry. Environ Health Perspect 113:1196–1204(2005). doi:10.1289/ehp.7974 available via http://dx.doi.org/ [Online 19 May 2005]

must be modified to detect As at the 50 µg/Lnational standard. The second kit is inaccurateand must be modified to avoid under-estimating the true concentration of As. Aftermodification, this second kit overestimates thetrue concentration of As (Geen et al. 2005). Asa result of these deficiencies, there is an urgentneed to supplement and ultimately replacethese field kits with a quantitative, accurate,precise, sensitive, inexpensive, and environ-mentally safe laboratory method for measuringAs in Bangladesh’s drinking water. The devel-opment and evaluation of such a laboratorymethod are reported here for the first time.

This new method uses relatively inexpen-sive reagents and equipment that are easilyobtained in Bangladesh and can be used tomeasure a wide variety of analytes. By design, ituses the same equipment as the silver diethyl-dithiocarbamate [AgSCSN(CH2CH3)2]method for measuring As [American PublicHealth Association (APHA) et al. 1989], whichis commonly used in Bangladesh. Therefore,the new method can be readily implementedin Bangladesh, and it does not require expen-sive equipment. Such resources are rare inBangladesh; for example, in 1997 there wasonly one atomic absorption spectrometer in theentire country that was used for the routineanalysis of As (USAID 1997). Also, it does notrequire highly specialized equipment, such asdevoted As analyzers, which have relatively highcost and limited utility (USAID 1997).

It is very important to realize that theWHO drinking water guideline for As of10 µg/L is based on a 6 × 10–4 excess lifetimeskin cancer risk for human males, which is60 times higher than the 1 × 10–5 factor thatis typically used to protect public health(WHO 1996). The WHO (1996) states thatthe drinking water guideline for As should be

0.17 µg/L based on the risk of death from skincancer. However, the detection limit for mostlaboratories is 10 µg/L, which is why the lessprotective guideline was adopted: “Guidelinevalues are not set at concentrations lower thanthe detection limit achievable under routinelaboratory operating conditions” (WHO1993, 1998).

Similarly, Bangladesh has limited access toatomic absorption spectrometers or othersophisticated instruments for measuring Asand uses a much higher 50 µg/L drinkingwater standard, largely because of the pooraccuracy of the AgSCSN(CH2CH3)2 method(USAID 1997). However, a 50 µg/L drinkingwater standard fails to protect against deathfrom not only skin cancer but also bladder,liver, and lung cancers. Drinking water with50 µg/L As may cause one extra death fromskin cancer per 500 people and one extradeath from bladder, liver, or lung cancer per300 people (Morales et al. 2000). Therefore,> 150,000 Bangladeshis are expected to diefrom skin, bladder, liver, or lung cancer caused

by drinking water with > 50 µg/L As. Morethan 120,000 of these lives could be saved ifBangladesh complied with the more protectiveWHO drinking water guideline for As of10 µg/L by sharing safe water within affectedneighborhoods. The present study suggeststhat Bangladesh could adopt this more protec-tive 10 µg/L guideline for As if it used thearsenomolybdate method for As measurement.

Materials and Methods

Sample Collection, Preservation,Shipment, and Analyses

Groundwater samples were collected fromfour neighborhoods in western Bangladesh(Fulbaria, Bualda, Jamjami, and Komlapur)during 18–21 July 2002 (Figure 1). A total of71 random samples were collected from67 tube wells in these four neighborhoods. Atotal of 18 random samples were collectedfrom 17 tube wells in each of three neighbor-hoods. In the fourth neighborhood, access wasdenied at 1 sampling location; therefore, a

An innovative method for measuring arsenic

Environmental Health Perspectives • VOLUME 113 | NUMBER 9 | September 2005 1197

647,000

642,000

637,000

632,000

627,000

622,000

Nor

thin

g (m

)

398,000 403,000 408,000 413,000Easting (m)

Jamjami

Garai River

Komlapur

Fulbaria

Bualda

Kushtia

Railro

ad

Sampling location+

Figure 1. Map of western Bangladesh showing thefour neighborhoods where groundwater sampleswere collected from tube wells. Kushtia is a majorcity.

Figure 2. As concentration (µg/L) in tube-well water at each sampling location by the arsenomolybdatemethod. (A) Fulbaria. (B) Bualda. (C) Jamjami. (D) Komlapur.

644,000

642,000

640,000

Nor

thin

g (m

)

407,000 409,000 411,000 413,000

399,000 401,000397,000 412,000 414,000

Easting (m) Easting (m)

647,000

645,000

626,000

624,000

622,000

639,500

637,500

635,500

Nor

thin

g (m

)

13

13

< 7

25

34

33

< 7< 7 < 7 < 7 < 7

< 799

74

< 7

200

8

< 7< 7

< 7

< 7< 7

< 7

< 7< 7 12 91

590

< 7

23100

22

240

< 7

< 7

< 7

< 7

< 7< 7

< 7< 7< 7

< 7 < 7 < 77

< 7

< 7

9

< 7

< 7

< 7

< 7

< 7

7

< 7< 7< 7

< 7

< 7

23

51

6126

54

BA

C D

19

43

Easting (m) Easting (m)

Nor

thin

g (m

)N

orth

ing

(m)

total of 17 random samples were collectedfrom 16 tube wells in that neighborhood.

To the extent possible, the sampled tubewells in each neighborhood were distributed at500-m intervals along perpendicular axes thatradiated in four equal lengths from the center(Figure 2). Two samples were collected fromthe centermost tube well in each neighborhood.One sample was collected from each of theremaining tube wells. The latitude and longi-tude of these tube wells were determined using aGarmin Global Positioning System 12 ChannelPersonal Navigator (Garmin International,Inc., Olathe, KS, USA). The accuracy of thisinstrument was approximately 15 m.

We used established collection, preserva-tion, and storage methodologies to ensurethat each sample was representative ofgroundwater quality (APHA et al. 1995;Stumm and Morgan 1981). Accordingly, allsampled tube wells were purged by pumpingvigorously for 10 min immediately beforesample collection. All samples were collected

directly into polyethylene bottles. These sam-ples were not filtered. Samples were analyzedimmediately after collection with pH paper,preserved by acidification to pH < 2 with5.0 M hydrochloric acid, and stored in ice-packed coolers. The temperature of all storedsamples was maintained at 0–4°C untilimmediately before analysis at laboratories inDubai and Vermont. In Dubai, all of thesesamples were analyzed for As by both thearsenomolybdate and AgSCSN(CH2CH3)2methods. The samples were subsequentlyshipped to Vermont and analyzed for As bygraphite furnace atomic absorption spec-troscopy (GFAAS). Contour maps of the Asconcentration in tube-well water from thesefour neighborhoods were drawn (Figure 3) asdescribed under “Mapping.”

Quality Control of LaboratoryAnalysesAll three methods for determining As werecalibrated daily. The calibration for the

AgSCSN(CH2CH3)2 method used five differ-ent standards, including a blank. The calibra-tions for the arsenomolybdate and GFAASmethods used six different standards, includ-ing blanks. All calibration standards were pre-pared from the same stock As solution. Theconcentration of the most dilute nonblankstandard was between 1 and 10 times themethod detection limit. Calibration checkstandards were analyzed every 20 samples andas the last analysis of each day to assess dataquality. An externally supplied standard wasused to assess the accuracy of the calibrationstandards and calibration check standards(APHA et al. 1995).

We used the recovery of a known additionof standard to eight different samples to assessthe matrix effects of all three methods of deter-mining As. In addition, three types of precisionwere measured for each method from theanalysis of seven different standards (precisionof standards), the duplicate analyses of eightdifferent samples (precision of samples), andthe analysis of a known addition of standard toeight different samples (precision of knownadditions). The same eight samples were usedto assess the matrix effects and precisions of allthree methods of determining As (Table 1;APHA et al. 1995).

Arsenomolybdate MethodApparatus. The apparatus, shown in Figure 4,includes an arsine (AsH3) generator (a 125 mLErlenmeyer flask), a scrubber (made from a10 mL volumetric pipette and a rubber stop-per), and an absorber (made from a 20 mLvolumetric pipette, a rubber stopper, and apolyethylene cap). The cap of the absorber hasfour grooves cut along its side to vent H2 gaswithout the loss of liquid during AsH3 genera-tion. The spectrophotometer (product no.6305; Jenway, Essex, UK) was set at 835 nmand used a 1.0 cm glass cell. All glassware wasacid washed in 1.00 M HCl.

Reagents. We purchased concentrated sul-furic acid (H2SO4; product no. 102766H) andconcentrated HCl (product no. 101256J) fromBDH Laboratory Supplies and zinc (20-meshgranules; product no. 24,346-9) from AldrichChemical Company (Milwaukee, WI, USA).

As solutions. We prepared the As solutionby dissolving 4.0 g sodium hydroxide (productno. 131687; Panreac Química S.A., Barcelona,Spain) in 10 mL distilled water; arsenic tri-oxide (1.320 g; product no. 22,762-5; Aldrich)was added, and the solution was diluted to1,000 mL with distilled water. An intermedi-ate As solution was prepared by diluting5.00 mL stock As solution to 500 mL withdistilled water. This intermediate solution wasthen used to prepare a standard As solution(10.00 mL intermediate As solution dilutedto 100 mL distilled water, which was used inthe experiments.

Frisbie et al.

1198 VOLUME 113 | NUMBER 9 | September 2005 • Environmental Health Perspectives

644,000

642,000

640,000

Nor

thin

g (m

)

407,000 409,000

AB

C

D

411,000 413,000

647,000

645,000

Easting (m) Easting (m)

626,000

624,000

622,000

Nor

thin

g (m

)

397,000 399,000 401,000 412,000 414,000

639,500

637,500

635,500

10 µg/L

50 µg/L

100 µg/L

Nor

thin

g (m

)N

orth

ing

(m)

Easting (m) Easting (m)

Sampling locationX

Figure 3. Contour maps of As concentration (µg/L) in tube-well water at each sampling location in the fourneighborhoods by the arsenomolybdate method. (A) Fulbaria. (B) Bualda. (C) Jamjami. (D) Komlapur. Theblack contour line represents the 10 µg/L WHO drinking water guideline.

Potassium iodide (50.0% wt/vol). Fiftygrams of KI (product no. 102123B; BDHLaboratory Supplies, Poole, UK) was dilutedto 100 mL with distilled water and stored inthe dark until use.

Stannous chloride dihydrate (40.0%wt/vol). Forty grams of stannous chloride dihy-drate (SnCl2·2H2O; product no. 102704Q;BDH Laboratory Supplies) was dissolved anddiluted to 100 mL with concentrated HCl.

Lead(II) acetate trihydrate (10.0%wt/vol). Pb(COOCH3)2·3H2O (10.0 g; prod-uct no. 21,590-2; Aldrich) was dissolved anddiluted to 100 mL with distilled water.

Iodine/KI. Twenty grams of KI was dis-solved in approximately 250 mL distilledwater; 12.5 g I2 (product no. 20,777-2;Aldrich) was added, and the solution wasmixed for several hours using a Teflon-coatedmagnetic stir bar until all the I2 dissolved.The solution was then diluted to 500 mLwith distilled water and stored in the dark.The solution was prepared fresh weekly.

Sodium bicarbonate (1.00 M). NaHCO3(product no. 102474V; BDH LaboratorySupplies) was dissolved and diluted to 100 mLwith distilled water.

Sulfuric acid/ammonium molybdatetetrahydrate. We prepared 100 mL of6.50 M H2SO4 in distilled water. We thendiluted 6.9 g (NH4)6Mo7O24·4H2O (productno. 100282H; BDH Laboratory Supplies) to100 mL with distilled water. Finally, the6.50 M H2SO4 and the 6.9% (wt/vol)(NH4)6Mo7O24·4H2O were mixed together.

Sodium metabisulfite (6.00%wt/vol). Sixgrams of Na2S2O5 (product no. 301804E;BDH Laboratory Supplies) were diluted to100 mL with distilled water; the solution wasprepared fresh daily.

Stannous chloride dihydrate (0.20%wt/vol). Fifty milliliters of 40.0% (wt/vol)SnCl2·2H2O was diluted to 100 mL with dis-tilled water; the solution was prepared freshdaily.

Sample treatment. In order to reduceAs(V) to As(III), 35.0 mL of either sample orstandard was mixed with 0.35 mL of 50.0%(wt/vol) KI and 0.35 mL of 40.0% (wt/vol)SnCl2·2H2O in a 125 mL Erlenmeyer flask (tobe used as the AsH3 generator). The mixture

was boiled 1.0 min to reduce As(V) to As(III),and a water bath was used to cool the mixtureto room temperature.

Scrubber preparation. The scrubber wasprepared by placing 0.17 ± 0.03 g glass wool(product no. 18421; Riedel-de Hafin; Seelze,Germany) onto a piece of Whatman filterpaper (Whatman, Kent, UK). Ten drops of10.0% (wt/vol) Pb(COOCH3)2·3H2O wasthen added to this piece of glass wool, and theglass wool was squeezed in the filter paper toremove the excess solution. The glass woolwas then fluffed and placed in the scrubber(Figure 4).

Absorber preparation. The absorber wasprepared by first adding 2.50 mL I2/KI solu-tion to a 20 mL test tube; 0.50 mL 1.00 MNaHCO3 was then added. This solution waspoured into the absorber and the cap wasplaced on the absorber (Figure 4).

Arsine generation, color development, andspectrophotometry. The amount of time foreach step of this procedure, from adding con-centrated H2SO4 to measuring the absorbance,was consistent for all samples and all stan-dards. Two milliliter of concentrated H2SO4was mixed with the treated sample or treatedstandard in the 125-mL Erlenmeyer flask(the AsH3 generator); after adding and mixing10.0 mL concentrated HCl and 1.0 mL 40.0%(wt/vol) SnCl2·2H2O, 5.0 g Zn was added.The scrubber and absorber were then con-nected to the AsH3 generator (Figure 4). Weallowed 30 min for the AsH3 to completelyevolve from the AsH3 generator to the absorber.

The liquid from the absorber was pouredinto a test tube calibrated to receive 5.00 mL;0.50 mL of distilled water was then used torinse the residual liquid from the absorber tothe test tube. One milliliter of H2SO4/(NH4)6Mo7O24·4H2O solution was added tothe test tube and mixed. Then 0.50 mL of6.00% (wt/vol) Na2S2O5 solution was addedto the test tube and mixed. The Na2S2O5changed the mixture from deep reddishbrown to faint yellow (the brown color mustbe eliminated). When necessary, distilledwater was added to until the total volume ofliquid was 5.00 mL. Then 0.50 mL 0.20%(wt/vol) SnCl2·2H2O was added and mixed.After waiting 30 min for the bluish green

arsenomolybdate color to develop, we meas-ured the absorbance at 835 nm.

Calibration. For calibration, we added 0,0.50, 1.00, 2.00, 4.00, and 8.00 mL of stan-dard As solution into six separate 125 mLErlenmeyer flasks and added distilled wateruntil the total volume of liquid in each flaskequaled 35.0 mL (Figure 4). The resultingstandards contained 0, 0.50, 1.00, 2.00, 4.00,and 8.00 µg of As or 0, 14, 28.6, 57.1, 114,and 229 µg/L, respectively. We used the sam-ple treatment, scrubber preparation, absorberpreparation, AsH3 generation, color develop-ment, and spectrophotometry proceduresdescribed above to analyze these standards.We confirmed that the calibration results fol-low Beer’s law; that is, we tested for a higherorder polynomial relationship to confirm lin-earity, and we tested the null hypothesis thatthe y-intercept goes through the origin (Neteret al. 1985).

Ultraviolet/Visible Spectrum ofArsenomolybdateIn order to determine the absorption maxi-mum of arsenomolybdate we measured theabsorption spectra of three arsenomolybdatesamples using an Agilent 8453 ultraviolet/visi-ble spectroscopy system (Agilent Technologies,Palo Alto, CA, USA). The wavelengths ofthese spectra ranged from 190 to 1,100 nm.Each arsenomolybdate sample was preparedfrom a 229 µg/L As standard solution usingthe sample treatment, scrubber preparation,absorber preparation, AsH3 generation, colordevelopment, and spectrophotometry pro-cedures described above under “Arseno-molybdate Method.” The spectrum of eacharsenomolybdate sample was measured relative

An innovative method for measuring arsenic

Environmental Health Perspectives • VOLUME 113 | NUMBER 9 | September 2005 1199

Scrubber

Absorber

AsH3 generator

10 cm

Figure 4. The AsH3 generator, scrubber, andabsorber used for the two colorimetric determina-tions of As.

Table 1. Quality control results, equipment costs, and solvents for the determination of As by arsenomolybdate,AgSCSN(CH2CH3)2, and GFAAS methods.

Arsenomolybdate AgSCSN(CH2CH3)2 GFAAS

Method detection limit 7 µg/L 9 µg/L 0.7 µg/LEquipment cost $6,700a $6,700a $37,000b

Recovery of known additionsc 101.5 ± 3.6% 103 ± 18% 103.3 ± 3.1%Precision of standards 2.1 µg/L 2.6 µg/L 0.22 µg/LPrecision of samples 4.7 µg/L 4.5 µg/L 1.7 µg/LPrecision of known additions 7.1 µg/L 24 µg/L 2.0 µg/LSolvent H2O CHCl3 or C5H5N H2OaIncludes a spectrophotometer, distillation unit for purifying laboratory water, analytical balance, top-loading balance, hotplate with stirrer, and glassware. bIncludes an atomic absorption spectrometer, distillation unit for purifying laboratorywater, analytical balance, top-loading balance, and glassware. c95% confidence interval.

to a blank. Similarly, each blank was preparedfrom a 0 µg/L As standard solution using theseprocedures. Each spectrum was measured after30 min of color development.

AgSCSN(CH2CH3)2 MethodWe analyzed all samples for As following theAgSCSN(CH2CH3)2 method of APHA et al.(1989). In this method, a 125-mL specimenjar was used for the AsH3 generator. Thescrubber and absorber were identical to thoseused for the “Arsenomolybdate Method”shown in Figure 4. A 35.0 mL aliquot ofsample or standard was placed in the AsH3generator and treated with 5.0 mL concen-trated HCl, 2.00 mL 15.0% (wt/vol) KI indistilled H2O, and 0.40 mL 40.0% (wt/vol)SnCl2·2H2O in concentrated HCl to reduceAs(V) to As(III). This reduction was allowed15 min for completion at room temperature.The scrubber was prepared as described abovefor the “Arsenomolybdate Method.” Theabsorber received 4.00 mL 0.50% (wt/vol)AgSCSN(CH2CH3)2 in pyridine (C5H5N).Then, 3.0 g Zn was added to the sample orstandard to generate AsH3. After 30 min ofAsH3 generation, the absorbate was measuredspectrophotometrically at 535 nm.

GFAAS MethodAll samples were analyzed for As by GFAASwith a Buck Scientific 220AS autosampler,220GF graphite furnace, and 210VGP atomicabsorption spectrometer (Buck Scientific, EastNorwalk, CT, USA). A 1.00 mL aliquot ofstandard As solution, sample, or diluted sam-ple was loaded onto the autosampler. The sixstandards contained 0, 1.0, 5.0, 15.0, 30.0,and 50.0 µg/L As, respectively. The matrix ofeach 1.00 mL aliquot was modified with50.0 µL 10.0% (wt/vol) ammonium nitrate(NH4NO3; product no. A1216; SpectrumChemicals and Laboratory Products, NewBrunswick, NJ, USA) in deionized water,50.0 µL 0.2% (wt/vol) palladium nitrate[Pd(NO3)2] in 2% (wt/vol) HNO3 (productno. K, Buck Scientific), and 50.0 µL 1.79%(wt/vol) magnesium nitrate hexahydrate[Mg(NO3)2·6H2O; product no. 5855-1; EMScience, Gibbstown, NJ, USA] in deionizedwater. The autosampler delivered a 20.0 µL

aliquot of this mixture to the graphite furnace.The furnace tube was made from nonpyrolyticgraphite (product no. BS300-1253; BuckScientific). The furnace initialized at 100°Cfor 10 sec, heated to 250°C for 20 sec, driedthe mixture at 250°C for 15 sec, heated to750°C for 25 sec, ashed the mixture at 750°Cfor 10 sec, heated to 2,200°C for 1.5 sec, andatomized the mixture at 2,200°C for 3 sec.The sheath and internal flows of argon gaswere 1,200 and 200 mL/min, respectively.The absorbance from a hollow-cathode lampwas read at 193.7 nm through a 0.7 nm slitand after deuterium (D2) background correc-tion. This absorbance was measured for2.4 sec during atomization. Finally, thisabsorbance over time was used to calculate Asconcentration (Buck Scientific Inc. 2002;Harris 1999).

StatisticsWe measured all 71 samples from this studyfor As by the arsenomolybdate, AgSCSN(CH2CH3)2, and GFAAS methods. We useda paired t-test of the As concentrations fromthese samples to determine if the arseno-molybdate and AgSCSN(CH2CH3)2 methodsgave equivalent or different results (Table 2);a second paired t-test to determine if thearsenomolybdate and GFAAS methods gaveequivalent or different results (Table 3); anda third paired t-test to determine if theAgSCSN(CH2CH3)2 and GFAAS methodsgave equivalent or different results (Table 4).Each of these three paired t-tests was evaluatedat the 95% confidence level (Snedecor andCochran 1982).

We used an F-test to determine if twoprecision values were equivalent or different.The standard deviation indicates precision(Table 1; APHA et al. 1995), and a varianceis indicated by precision squared (Snedecorand Cochran 1982). A ratio of these variancesin an F-test show the equality of the corre-sponding precisions (Snedecor and Cochran1982). Each F-test was evaluated at the 95%confidence level.

MappingWe used the As concentration by the arseno-molybdate method, the sample location by

the Global Positioning System, and the SurferSurface Mapping System (version 7; GoldenSoftware Inc., Golden, CO, USA) to drawone contour map for each of the fourneighborhoods (Figure 3). To map the con-tours shown in Figure 3, we used a variogramto select the equation that best matched thespatial continuity of the actual As concentra-tions in each neighborhood (Figure 2). Weused inverse-distance weighted least-squaresequations (Shepard’s method) for Fulbariaand Bualda and a logarithmic equation forJamjami. We did not use an equation forKomlapur because all the samples in thisneighborhood had As concentrations≤ 10 µg/L, the WHO drinking water guide-line (WHO 1996).

Societal EvaluationInitial interview during sampling. One princi-pal user of each tube well was interviewed dur-ing groundwater sampling during 18–21 July2002. Each interview was conducted inBangla from a list of standard questions. Eachinterviewee was asked whether alternativedrinking water sources were available (rain,ponds, rivers, or canals), and the followinginformation was recorded: a) the number ofusers per tube well; b) the depth and age ofeach tube well; c) the results from previous Astests, if any; and d) whether any users wereknown to have melanosis, keratosis, gangrene,skin cancer, conjunctivitis, respiratory distress,or enlarged liver. Finally, the willingness ofeach interviewee to get safe drinking waterfrom their neighbors or to give safe drinkingwater to their neighbors was evaluated.

Distributing As results. Our field staffgave a Bangla-language form letter summariz-ing the neighborhood’s As results to eachinterviewee 6 months after their groundwaterwas sampled. In addition, the contents ofeach letter were explained in Bangla by ourfield staff. Therefore, each interviewee knew ifhis tube well had a safe or unsafe concentra-tion of As. Furthermore, each intervieweeknew which neighbor’s tube well had a safe orunsafe concentration of As.

Interviewees with As concentrations ≤ 10µg/L were informed that their tube wells weresafe with respect to this element. In addition,

Frisbie et al.

1200 VOLUME 113 | NUMBER 9 | September 2005 • Environmental Health Perspectives

Table 2. Comparison of As concentrations determinedby the arsenomolybdate and AgSCSN(CH2CH3)2methods.

Measure Result

Calculated t 1.88Critical two-tailed t at α = 0.05 (70 df) 1.99p-Value of paired t-test 0.06Correlation coefficient, r 0.993Mean As concentration by 27.6 µg/L

arsenomolybdateMean As concentration by 23.4 µg/L

AgSCSN(CH2CH3)2Relative percent difference of these means 16.6%

Table 3. Comparison of As concentrations deter-mined by the arsenomolybdate and GFAAS methods.

Measure Result

Calculated t 1.19Critical two-tailed t at α = 0.05 (70 df) 1.99p-Value of paired t-test 0.24Correlation coefficient, r 0.996Mean As concentration by 27.6 µg/L

arsenomolybdateMean As concentration by GFAAS 28.6 µg/LRelative percent difference of these 3.6%

means

Table 4. Comparison of As concentrations deter-mined by the AgSCSN(CH2CH3)2 and GFAAS methods.

Measure Result

Calculated t 2.63Critical two-tailed t at α = 0.05 (70 df) 1.99p-Value of paired t-test 0.01Correlation coefficient, r 0.995Mean As concentration by 23.4 µg/L

AgSCSN(CH2CH3)2Mean As concentration by GFAAS 28.6 µg/LRelative percent difference of these 20.1%

means

they were informed that their tube wellsshould be tested for As at least once a yearbecause the concentration of As can changeover time (Frisbie et al. 1999; USAID 1997).Finally, these interviewees were asked to sharetheir drinking water with those who couldnot get safe water from their own tube wells.

Interviewees with As concentrations> 10 µg/L (WHO drinking water guideline)were informed that their tube wells wereunsafe with respect to this element, and theimminent risk of serious health problems fromcontinuing to drink this water was thoroughlyexplained. Finally, they were asked to get safedrinking water from their neighbors.

Final interview 1 year after sampling.Each original interviewee, if available, wasrevisited 1 year after their groundwater wassampled and 6 months after they were giventhe As results for their neighborhood. If theoriginal interviewee was not available, then asurrogate interviewee was identified. Thesepeople were interviewed in Bangla from a listof standard questions. The purposes of thisfinal interview were to determine a) if the peo-ple with safe tube wells actually gave drinkingwater to their neighbors who did not have safedrinking water; b) whether the people withunsafe tube wells actually got safe drinkingwater from their neighbors; c) whether thepeople with safe water followed our instruc-tions and retested their tube wells for As; andd) the health status of all tube-well users.

Results and Discussion

Rationale for sampling drinking water inwestern Bangladesh. We chose westernBangladesh for this study because it has someof the widest ranges of groundwater As con-centrations in the country, according to ourtwo national-scale surveys (Frisbie et al. 1999,2002; USAID 1997). This variability is associ-ated with the complex mixture of flood plaindeposits that form western Bangladesh (Yuet al. 2003). As a result, the neighborhoods inwestern Bangladesh usually have at least onetube well that does not require treatment forAs removal before drinking (Frisbie et al. 1999;USAID 1997). For example, the As concentra-tions in our four randomly selected westernBangladeshi neighborhoods ranged from < 0.7to 590 µg/L, with 30% of samples > 10 µg/L,the WHO drinking water guideline (WHO1996). This makes western Bangladesh wellsuited for evaluating our laboratory method ofmeasuring As in drinking water. It is also wellsuited for determining whether people will usethe results from this method to share safedrinking water with their neighbors.

Independent evaluation of the arseno-molybdate method. The arsenomolybdate cali-bration obeys Beer’s law; that is, the plot ofabsorbance versus As concentration is linear,and the y-intercept goes through the origin. A

test for a higher order polynomial relationshipwas done for each daily calibration and rou-tinely confirmed this linearity at the 95% con-fidence level (Neter et al. 1985). Similarly, atest of the null hypothesis that the y-interceptgoes through the origin was performed for eachdaily calibration and routinely confirmed thatthe y-intercept was equivalent to 0, 0 at the95% confidence level (Neter et al. 1985). Thecalibration equation from the arsenomolybdatemethod detection limit study is absorbance =0.00169 × (micrograms As per liter), and thecorrelation coefficient (r) = 1.00. The slope ofthe equation and the 7 µg/L method detectionlimit shown in Table 1 suggest that the colori-metric measurement of As by arsenomolybdateis extremely sensitive. The 101.5 ± 3.6% recov-ery of known additions shown in Table 1 sug-gests that the results from the arsenomolybdatemethod are accurate. The respective 2.1, 4.7,and 7.1 µg/L precisions of standards, samples,and known additions shown in Table 1 suggestthat the results from the arsenomolybdatemethod are reproducible.

In this method, As is removed from thesample by reduction to AsH3 gas. This gas iscollected in an absorber by oxidation toarsenic acid (H3AsO4). All previous attemptsat this separation have suffered from poorreproducibility because of the incompleterecovery of AsH3 (Sandell 1942, 1959). Thesources of this incomplete recovery wereinsufficient concentrations of oxidant in theabsorbate, the deterioration of absorbate withtime, and improper absorber designs. Thisproblem of incomplete recovery has beensolved.

We discovered and corrected an error thathas not been reported by previous researchers.This error was from drift caused by thearsenomolybdate absorption spectrum chang-ing with time. Our method requires that thearsenomolybdate color develop for 30 minbefore its absorbance is measured. This color isrelatively stable after 30 min. In addition, a lossof sensitivity from using polychromatic light tomeasure absorbance has been corrected. Ourmethod requires that the absorbance be meas-ured at 835 nm, the absorption maximum ofarsenomolybdate. In addition, previousarsenomolybdate methods were not comparedwith established methods for measuring As(Milton and Duffield 1942; Sandell 1959).Comparisons of our method with theAgSCSN(CH2CH3)2 and GFAAS methods formeasuring As are shown in Tables 1–4.

Finally, all routine analytical methodsmust use a rigorous quality control plan toidentify and correct systematic errors. Thequality control plan for the arsenomolybdatemethod should include daily calibrations andthe frequent analysis of blanks, externally sup-plied standards, calibration check standards,duplicate samples, and known additions of

standard to samples (APHA et al. 1995;Frisbie et al. 1999; USAID 1997).

Arsenomolybdate versus AgSCSN(CH2CH3)2. We found no difference betweenthe arsenomolybdate and AgSCSN(CH2CH3)2methods for measuring As at the 95% confi-dence level, according to a paired t-test of all71 samples from this study (p-value = 0.06;Table 2). As a result, these two methods arehighly correlated (r = 0.993; Table 2). Thesetwo methods can quantify As to less than theWHO drinking water guideline of 10 µg/Lwithout expensive or highly specialized labora-tory equipment; the cost and required skill toimplement these methods are comparable; theprecisions of standards for the methods areequivalent at the 95% confidence level; andthe precisions of samples for the two methodsare equivalent at the 95% confidence level(Table 1).

However, the precision values of knownadditions for the arsenomolybdate andAgSCSN(CH2CH3)2 methods are different atthe 95% confidence level (Table 1). Thesetwo precision values were measured using thesame eight samples. This suggests that theAgSCSN(CH2CH3)2 method is imprecise atrelatively high As concentrations because ofthe sample matrix. Additional evidence of thisimprecision is the 16.6% relative percent dif-ference of the mean As concentrations from all71 samples measured by the arsenomolybdateand AgSCSN(CH2CH3)2 methods (Table 2).One source of this imprecision may be theincomplete reduction of As(V) to As(III) inBangladesh’s tube-well water by the relativelymild sample treatment procedure of theAgSCSN(CH2CH3)2 method. More specifi-cally, the arsenomolybdate method uses KIand SnCl2·2H2O at 100°C for this reduction,whereas the AgSCSN(CH2CH3)2 methoduses KI and SnCl2·2H2O at room tempera-ture. Another source of this imprecision maybe the incomplete generation of AsH3 inBangladesh’s tube-well water by the relativelymild AsH3 generation procedure of theAgSCSN(CH2CH3)2 method. More specifi-cally, the arsenomolybdate method uses 0.18 gKI, 0.540 g SnCl2·2H2O, 2.0 mL concentratedH2SO4, 10.0 mL concentrated HCl, and 5.0 gZn per 35.0 mL of sample for AsH3 generation.In contrast, the AgSCSN(CH2CH3)2 methoduses 0.300 g KI, 0.16 g SnCl2·2H2O, 5.0 mLconcentrated HCl, and 3.0 g Zn per 35.0 mLof sample for AsH3 generation.

Another important difference between thearsenomolybdate and AgSCSN(CH2CH3)2methods is related to worker health andenvironmental protection. More specifically,the arsenomolybdate method uses H2O as asolvent, which is nontoxic, nonflammable,and easy to dispose of. In contrast, theAgSCSN(CH2CH3)2 method uses eitherchloroform (CHCl3) or C5H5N as a solvent

An innovative method for measuring arsenic

Environmental Health Perspectives • VOLUME 113 | NUMBER 9 | September 2005 1201

(Table 1). All routes of exposure to CHCl3are likely to cause cancer in humans [U.S.Environmental Protection Agency (EPA)2004]. Moreover, with improper disposal,CHCl3 can persist in an aquifer for centuries(Pankow and Cherry 1996). Exposure toC5H5N may cause increased liver weight andhepatic lesions (U.S. EPA 2004). In addition,C5H5N is highly flammable and, as a result,presents an acute risk to laboratory workers(Sittig 1985).

In summary, the arsenomolybdate methodis more accurate and precise than theAgSCSN(CH2CH3)2 method based on therecoveries of known additions (Tables 1and 2). The arsenomolybdate method is saferthan the AgSCSN(CH2CH3)2 method becauseit does not use toxic solvents (Table 1).

Arsenomolybdate versus GFAAS. Wefound no difference between the arsenomolyb-date and GFAAS methods for measuring As atthe 95% confidence level, according to apaired t-test of all 71 samples (p-value = 0.24;Table 3). As a result, these two methods arehighly correlated (r = 0.996; Table 3). Bothmethods can quantify As to less than the10 µg/L WHO drinking water guideline(WHO 1996; Table 1). However, the equip-ment cost for the GFAAS method is muchgreater than that for the arsenomolybdatemethod (Table 1).

Despite its far lower cost, the arseno-molybdate method is more accurate than theGFAAS method. The recovery of knownadditions by the arsenomolybdate method isequivalent to 100% (101.5 ± 3.6%; Table 1).In contrast, the recovery of known additionsby the GFAAS method is > 100% (103.3 ±3.1%; Table 1). This suggests that theGFAAS method overestimated the true con-centration of As in this matrix by approxi-mately 3.3% (Table 1). This estimate of 3.3%bias by the GFAAS method is based on therecovery of known additions from eight sam-ples. Additional evidence of this bias is the3.6% relative percent difference of the meanAs concentrations from all 71 samples mea-sured by the arsenomolybdate and GFAASmethods (Table 3). This overestimation bythe GFAAS method was likely caused by scat-tered light from sodium chloride or similarmatrix salts that remained in the furnace dur-ing atomization (Frisbie et al. 1999, 2002;Harris 1999; USAID 1997). If so, theNH4NO3, Pd(NO3)2, and Mg(NO3)2·6H2Omatrix modifiers and D2 background correc-tion did not fully resolve this interference.

In contrast, the GFAAS method is moreprecise than the arsenomolybdate method.The standards, samples, and known additionsare measured with greater precision by theGFAAS method than by the arsenomolybdatemethod (Table 1). Each of these three F-testswas evaluated at the 95% confidence level.

In summary, the arsenomolybdate methodis more accurate and affordable than theGFAAS method (Tables 1 and 3).

AgSCSN(CH2CH3)2 versus GFAAS. TheAgSCSN(CH2CH3)2 and GFAAS methodsfor measuring As are different at the 95%confidence level, according to a paired t-testof all 71 samples (p-value = 0.01; Table 4).Furthermore, the As concentrations measuredby the GFAAS method were approximately20.1% greater than those measured by theAgSCSN(CH2CH3)2 method (Table 4).The difference between these methods waslikely caused by a combination of two defi-ciencies: the observed imprecision of theAgSCSN(CH2CH3)2 method at relativelyhigh As concentrations, and the observedbias of the GFAAS method at all As concen-trations.

Societal evaluation. Any society mayaccept or reject a given solution to a problemfor a variety of reasons. Therefore, it is essen-tial to evaluate the willingness of Bangladeshisto use the results from our method to obtainsafe drinking water with As concentrations10 µg/L from their own wells or from theirneighbors, and to give this “safe” drinkingwater to their neighbors.

Water testing and sharing can provideaccess to safe drinking water for the millionsof Bangladeshis who live in communitieswhere some tube wells are safe and others arenot (Frisbie et al. 1999, 2002; USAID 1997).Whether or not this testing and sharing willactually provide safe drinking water in thesecommunities will depend on neighbors cor-rectly understanding the As results for theirtube wells and consistently sharing safe waterwith each other. However, water gatheringand use are subject to cultural habits that aredifficult to change. The nearly universalswitch (97%) in Bangladesh since 1971 fromusing surface water for drinking to tube-wellwater has shown that water use traditions canbe changed, provided there are extensive com-munity education programs and support fromboth the government and nongovernmentalorganizations (WHO 2000).

In Bangladesh, as in most other areaswhere water must be gathered from a com-munal source, the chore of water gathering isgenerally considered to be women’s work.However, Bangladeshi women are con-strained by society and their families to stayclose to home, whereas unrelated men aregenerally not welcome inside family com-pounds. In order for water testing and sharingto be successful as a strategy for providing safedrinking water in Bangladesh, the neighborsas a community must be educated about themeaning of their As results. They must alsobe willing to use tube wells that may not beclose to home or to share their own safe tubewells with unrelated neighbors or strangers.

In our initial survey, which was completedbefore the owner or regular user of each tubewell knew the results from our testing, weasked respondents if they would be willing touse other water sources if their own tube wellhad unsafe levels of As. We also asked them ifthey would be willing to share water with theirneighbors if their own tube well turned out tobe safe. The results were very encouraging;86% of respondents claimed they would per-mit family members to gather water from othertube wells if their own tube well had unsafelevels of As, and 94% said they would sharewater with neighbors if they had safe water andtheir neighbors did not have safe water.

However, what people say they will do isnot always what they actually do in practice.For this reason, we conducted a follow-up sur-vey 6 months after our testing results were dis-tributed to the original respondents or theirfamily members. In this second survey, welearned that almost all tube-well owners (91%)shared water with others. Many respondentsnoted that sharing water with strangers is cus-tomary in village communities and required asa matter of courtesy or charity, which seems tooverride issues of water safety. Generally, how-ever, after As testing, the status of a tube wellbecomes known in the community. Once Astest results become known in the community,only strangers continue to ask for water fromcontaminated tube wells. Owners of safe tubewells report that the largest group of non-family members gathering water at their tubewells are neighbors, and 26% of these ownersclaimed that one reason why they shared theirwater was because other tube wells had unsafelevels of As and theirs did not.

Instead of sending women out to get waterfrom a stranger’s tube well, men in some fami-lies took over this chore. Some men go to pub-lic tube wells at mosques to gather water fortheir families. Others seek water from neigh-bors’ or relatives’ tube wells. However, this wascited as a source of conflict by 11% of tube-well owners, who did not like having unrelatedmen enter their family compounds. The loca-tion of a tube well is crucial. If the tube well islocated on the street, then all may use it freely.In contrast, if the tube well is located inside afamily compound, only family members andcertain relatives have free access to the com-pound and the tube well, regardless of thestated willingness of the owner to share thetube well. Distance is also a factor for willing-ness to gather water from an outside tube well,with one family reporting that it continued touse As-contaminated water because other tubewells were too far away. The maximum dis-tance required to get safe drinking water ineach of these four neighborhoods was approxi-mately 0 m in Komlapur, 490 m in Bualda,1,400 m in Fulbaria, and 2,100 m in Jamjami(Figure 3).

Frisbie et al.

1202 VOLUME 113 | NUMBER 9 | September 2005 • Environmental Health Perspectives

Education programs concerning the dan-gers of As-contaminated water have achievedsome measure of success, because only oneowner of an unsafe tube well in our studyappeared not to have understood the implica-tions of his tube well’s As results. This owner,a 70-year-old male, professed during the fol-low-up interview that his water was safe, andhe told us that he had continued to use it andshare it freely with others.

Many of the tube-well owners (85%) fol-lowed our recommendation and had theirtube wells retested. This retesting was not per-formed by our research team. Only onerespondent told us that he thought retestingwas not necessary (the one who believed hiswater was safe when it was not); the otherswho did not retest their water gave cost as thereason for not retesting. People were especiallywilling to retest their water if this could bedone at no cost to them. Of the respondentswho had their water retested, 96% reportedthat the retesting was done with no charge tothem; however, two respondents paid to havetheir water retested.

Our survey suggests that the number oftube wells, especially private tube wells, israpidly increasing in Bangladesh as more fami-lies acquire the economic resources to build

them. Only 14% of tube wells were reportedto have been constructed before 1983 (56%private); 27% were reported to have been con-structed from 1983 to 1992 (83% private),and 59% from 1993 to 2002 (92% private),making the tube wells in our random samplefrom western Bangladesh only 9 years old onaverage. In addition, we asked whetherrespondents were aware of any As patients inthe area. The number of nearby As patientswas not statistically related to the concentra-tion of As during our sampling event (p =0.44). Similarly, the concentration of As dur-ing our sampling event was not statisticallyrelated to the age of the tube well (p = 0.51).In contrast, the number of nearby As patientswas statistically related to the age of the tubewell and hence the duration of exposure totube-well water that was potentially contami-nated with As. That is, the oldest tube wellswere associated with the highest number ofnearby As patients (p = 0.03). This stresses thefact that duration of exposure to As must beconsidered in addition to the concentration ofAs at any given time, because this can explainwhy the tube wells of some As patients arefound to contain very low levels of As buthave been used over many years (WHO2001). For example, Figure 5 shows a femaleAs patient with keratosis of the palms andblackfoot disease. When tested in 2002, thetube well used by this patient had an As con-centration of 1.4 µg/L, but she had beendrinking from this tube well for 34 years. TheAs concentration in some of Bangladesh’s tubewells has changed dramatically over time(Frisbie et al. 1999; USAID 1997). Theseresults demonstrate the need to periodicallytest all drinking water tube wells so that thetotal lifetime exposure to As can be reduced.Because most of the tube wells in the countryhave been installed quite recently, the num-bers of As patients may begin to increase dra-matically as more people develop a history ofusing tube wells for longer than the 5–10 yearsit may take to develop symptoms of chronicAs poisoning. Finally, as the ages of the tubewells and the length of exposure to Asincrease, it may become even more vital toadopt a drinking-water standard for As lowerthan the current Bangladesh standard of50 µg/L, such as the 10 µg/L WHO guideline(WHO 1996).

Conclusions

A valid method for the determination of As byarsenomolybdate is now available. Thismethod is more accurate, precise, and environ-mentally safe than the AgSCSN(CH2CH3)2method (Tables 1 and 2), and it is more accu-rate and affordable than the GFAAS method(Tables 1 and 3).

Most important, the arsenomolybdatemethod is the only accurate, precise, and safe

way to quantify As to less than the 10 µg/LWHO drinking water guideline (WHO1996) without expensive or highly specializedlaboratory equipment (Table 1). This suggeststhat developing countries such as Argentina,Bangladesh, Bolivia, Chile, China, India,Mexico, Nepal, Pakistan, Peru, and Thailand,with limited access per capita to atomicabsorption spectrometers or other sophisti-cated instruments for measuring As, couldlower their 50 µg/L drinking water standardsto the more protective 10 µg/L guidelineif they use the arsenomolybdate method(Bhattacharya et al. 2002; Ng et al. 2003;United Nations 2004). More than 32 millionpeople from these countries drink water withAs concentrations greater than their nationalstandards of 50 µg/L (Bhattacharya et al.2002; Ng et al. 2003; United Nations 2004;Yu et al. 2003). This suggests that > 170,000people from these countries will die fromskin, bladder, liver, or lung cancer caused bydrinking water with > 50 µg/L As. If thesecountries complied with a 10 µg/L drinkingwater standard for As, perhaps by sharing safewater as was done in the four neighborhoodsfrom this study, > 140,000 of these 170,000lives could potentially be saved.

In particular, it is very important that theGovernment of Bangladesh lower its 50 µg/Ldrinking water standard for As. The rapidlyincreasing number of tube wells in Bangladeshsuggests that the mortality rate from chronicAs poisoning is also rapidly increasing.Lowering this standard will reduce exposureand save lives by encouraging the use of saferdrinking water.

Finally, our surveys suggest thatBangladeshis will readily test and share theirdrinking water to meet the more protectiveWHO guideline for As of 10 µg/L. Morespecifically, 85% of tube-well owners wereconcerned enough to retest their water for Aswithin 1 year, and 90% of the tube-well own-ers that had tube-well As concentrations> 10 µg/L actually gathered water from theirneighbors.

REFERENCES

APHA, American Water Works Association, Water PollutionControl Federation. 1989. Standard Methods for theExamination of Water and Wastewater. 17th ed.Washington, DC:American Public Health Association.

APHA, American Water Works Association, Water EnvironmentFederation. 1995. Standard Methods for the Examination ofWater and Wastewater. 19th ed. Washington, DC:AmericanPublic Health Association.

BGS. 1999a. Groundwater Studies for Arsenic Contamination inBangladesh, Main Report. Nottingham, UK:BritishGeological Survey.

BGS. 1999b. Groundwater Studies for Arsenic Contamination inBangladesh, Vol S5. Nottingham, UK:British GeologicalSurvey.

Bhattacharya P, Jacks G, Frisbie SH, Smith E, Naidu R, Sarkar B.2002. Arsenic in the environment: a global perspective. In:Heavy Metals in the Environment (Sarkar B, ed). NewYork:Marcel Dekker Inc., 147–215.

An innovative method for measuring arsenic

Environmental Health Perspectives • VOLUME 113 | NUMBER 9 | September 2005 1203

Figure 5. Photograph of a Bangladeshi female withkeratosis of the palms and blackfoot disease. Herwell contained 1.4 µg/L As on 21 July 2002; she hadbeen drinking from this well for 34 years.

Frisbie et al.

1204 VOLUME 113 | NUMBER 9 | September 2005 • Environmental Health Perspectives

Buck Scientific, Inc. 2002. Buck Scientific 210VGP AtomicAbsorption Spectrophotometer Operator’s Manual. EastNorwalk, CT:Buck Scientific, Inc.

Frisbie SH, Maynard DM, Hoque BA. 1999. The nature and extentof arsenic-affected drinking water in Bangladesh. In: Metalsand Genetics (Sarkar B, ed). New York:Plenum, 67–85.

Frisbie SH, Ortega R, Maynard DM, Sarkar B. 2002. The concen-trations of arsenic and other toxic elements in Bangladesh’sdrinking water. Environ Health Perspect 110:1147–1153.

Geen AV, Cheng Z, Seddique AA, Hoque MA, Gelman A,Graziano JH, et al. 2005. Reliability of a commercial kit totest groundwater for arsenic in Bangladesh. Environ SciTechnol 39:299–303.

Harris DC. 1999. Quantitative Chemical Analysis. 5th ed. NewYork:W.H. Freeman.

Milton R, Duffield WD. 1942. Determination of arsenic in soils,foods, organic compounds, etc. Analyst 67:279–283.

Monan J. 1995. Bangladesh: the Strength to Succeed. Oxford,UK:Oxfam.

Morales KH, Ryan L, Kuo TL, Wu MM, Chen CJ. 2000. Risk ofinternal cancers from arsenic in drinking water. EnvironHealth Perspect 108:655–661.

Neter J, Wasserman W, Kutner MH. 1985. Applied LinearStatistical Models. 2nd ed. Homewood, IL:Irwin.

Ng JC, Wang J, Shraim A. 2003. A global health problemcaused by arsenic from natural sources. Chemosphere52:1353–1359.

Nyrop RF, Benderly BL, Conn CC, Cover WW, Eglin DR. 1975.Area Handbook of Bangladesh. Washington, DC:AmericanUniversity.

Pankow JF, Cherry JA. 1996. Dense Chlorinated Solvents andOther DNAPLs in Groundwater. Portland, OR:Waterloo Press.

Sandell EB. 1942. Colorimetric microdetermination of arsenicafter evolution as arsine. Ind Eng Chem 14:82–83.

Sandell EB. 1959. Colorimetric Determination of Traces ofMetals. 3rd ed. New York:Interscience Publishers, Inc.

Sittig M. 1985. Handbook of Toxic and Hazardous Chemicals andCarcinogens. 2nd ed. Park Ridge, NJ:Noyes Publications.

Snedecor GW, Cochran WG. 1982. Statistical Methods. 7th ed.Ames, IA:Iowa University Press.

Stumm W, Morgan JJ. 1981. Aquatic Chemistry. NewYork:John Wiley & Sons.

United Nations. 2004. United Nations Children’s Fund and PakistanCouncil of Research in Water Resources Collaborating toCounter Arsenic Contamination. Available: http://www.un.org.pk/unic/newsletters/NEWSLETTER040309.htm [accessed24 March 2004].

UNICEF. 2004. Summary of Midterm Reviews and MajorEvaluations of Country Programmes. Available: http://www.unicef.org/about/exeboard/files/04-PL31.pdf [accessed19 November 2004].

USAID. 1997. Report of the Impact of the Bangladesh RuralElectrification Program on Groundwater Quality. Dhaka,Bangladesh:U.S. Agency for International Development.

U.S. EPA (United States Environmental Protection Agency).2004. Integrated Risk Information System. Available:http://www.epa.gov/iris/ [accessed 1 April 2004].

WHO. 1993. Guidelines for Drinking-Water Quality, Volume 1:Recommendations. 2nd ed. Geneva, Switzerland:WorldHealth Organization.

WHO. 1996. Guidelines for Drinking-Water Quality, Volume 2:Health Criteria and Other Supporting Information. 2nd ed.Geneva, Switzerland:World Health Organization.

WHO. 1998. Guidelines for Drinking-water Quality, Addendumto Volume 1: Recommendations. 2nd ed. Geneva,Switzerland:World Health Organization.

WHO. 2000. Arsenic Contamination of Drinking Water inBangladesh. Available: http://www.who.int/peh-super/Oth-lec/Arsenic/Series1/002.htm [accessed 2 May 2000].

WHO. 2001. Arsenic and Arsenic Compounds (EHC 224, 2001).Available: http://www.inchem.org/documents/ehc/ehc/ehc224.htm#1.7 [accessed 22 July 2004].

WHO. 2003. Fact Sheet #210: Arsenic in Drinking Water.Available: http://www.who.int/inf-fs/en/fact210.html[accessed 24 May 2003].

Yu WH, Harvey CM, Harvey CF. 2003. Arsenic in groundwater inBangladesh: a geostatistical and epidemiological frame-work for evaluating health effects and potential remedies.Water Res 39:1146–1162.