Validity of spatial models of arsenic concentrations in private well water

OBJECTIVE: Arsenic is a pervasive contaminant in underground aquifers worldwide, yet documentation of health effects associated with low-to-moderate concentrations (<100microg/L) has been stymied by uncertainties in assessing long-term exposure. A critical component of assessing exposure to arsenic in drinking water is the development of models for predicting arsenic concentrations in private well water in the past; however, these models are seldom validated. The objective of this paper is to validate alternative spatial models of arsenic concentrations in private well water in southeastern Michigan. METHODS: From 1993 to 2002, the Michigan Department of Environmental Quality analyzed arsenic concentrations in water from 6050 private wells. This dataset was used to develop several spatial models of arsenic concentrations in well water: proxy wells based on nearest-neighbor relationships, averages across geographic regions, and geostatistically derived estimates based on spatial correlation and geologic factors. Output from these models was validated using arsenic concentrations measured in 371 private wells from 2003 to 2006. RESULTS: The geostatisical model and nearest-neighbor approach outperformed the models based on geographic averages. The geostatistical model produced the highest degree of correlation using continuous data (Pearson's r=0.61; Spearman's rank rho=0.46) while the nearest-neighbor approach produced the strongest correlation (kappa(weighted)=0.58) using an a priori categorization of arsenic concentrations (<5, 5-9.99, 10-19.99, > or = 20microg/L). When the maximum contaminant level was used as a cut-off in a two-category classification (<10, > or =10microg/L), the nearest-neighbor approach and geostatistical model had similar values for sensitivity (0.62-0.63), specificity (0.80), negative predictive value (0.85), positive predictive value (0.53), and percent agreement (75%). DISCUSSION: This validation study reveals that geostatistical modeling and nearest-neighbor approaches are effective spatial models for predicting arsenic concentrations in private well water. Further validation analyses in other regions are necessary to indicate how widely these findings may be generalized.     

Respiratory effects and arsenic contaminated well water in Bangladesh

Arsenic in drinking water causes a widespread concern in Bangladesh, where a major proportion of tube wells is contaminated. Arsenic ingestion causes skin lesions, which is considered as definite exposure. A prevalence comparison study of respiratory effects among subjects with and without arsenic exposure through drinking water was conducted in Bangladesh. Exposed participants were recruited through health awareness campaign programs. Unexposed participants were randomly selected, where tubewells were not contaminated with arsenic. A total of 169 individuals participated (44 exposed individuals exhibiting skin lesions; 125 unexposed individuals). The arsenic concentrations ranged from 136 to 1000 micro g l(-1). The information regarding respiratory system signs and symptoms were also collected and the analyses were confined to nonsmokers. The crude prevalence ratio for chronic bronchitis and chronic cough amounted to 2.1 (95% CI 0.7-6.1). The prevalence ratios for chronic bronchitis increased with increasing exposure, i.e., 1.0, 1.6, 2.7 and 2.6 using unexposed as the reference. The prevalence ratios for chronic cough were 1.0, 1.6, 2.7 and 2.6 for the exposure categories, using the same unexposed as the reference. The dose-response trend was the same (P < 0.1) for both conditions. These results add to evidence that long-term ingestion of arsenic exposure can cause respiratory effects.     

Risk factors for increased urinary inorganic arsenic concentrations from low arsenic concentrations in drinking water

A large number of drinking water supplies worldwide have greater than 50 microg l(- 1) inorganic arsenic in drinking water, and there is increasing pressure to reduce concentrations. Few studies have specifically considered low concentrations of arsenic in water supplies and the significance of other factors which may contribute to increased exposure. This study aimed to investigate risk factors for increased urinary inorganic arsenic concentrations, in a population exposed to 10 - 100 microg l(- 1) of arsenic in drinking water, as well as a control population with lower arsenic concentrations in their drinking water. Inorganic arsenic in urine was used as the measure of exposure. The median drinking water arsenic concentration in the exposed population was 43.8 microg l(- 1) (16.0 - 73 microg l(- 1)) and less than the analytical limit of detection of 1 microg l(- 1) (相似文献   

Variability in human metabolism of arsenic

Estimating the nature and extent of human cancer risks due to arsenic (As) in drinking water is currently of great concern, since millions of persons worldwide are exposed to arsenic, primarily through natural enrichment of drinking water drawn from deep wells. Humans metabolize and eliminate As through oxidative methylation and subsequent urinary excretion. While there is debate as to the role of methylation in activation/detoxification, variations in arsenic metabolism may affect individual risks of toxicity and carcinogenesis. Using data from three populations, from Mexico, China, and Chile, we have analyzed the distribution in urine of total arsenic and arsenic species (inorganic arsenic (InAs), monomethyl arsenic (MMA), and dimethyl arsenic (DMA). Data were analyzed in terms of the concentration of each species and by evaluating MMA:DMA and (MMA+DMA):InAs ratios. In all persons most urinary As was present as DMA. Male:female differences were discernible in both high- and low-exposure groups from all three populations, but the gender differences varied by populations. The data also indicated bimodal distributions in the ratios of DMA to InAs and to MMA. While the gene or genes responsible for arsenic methylation are still unknown, the results of our studies among the ethnic groups in this study are consistent with the presence of functional genetic polymorphisms in arsenic methylation leading to measurable differences in toxicity. This analysis highlights the need for continuing research on the health effects of As in humans using molecular epidemiologic methods.     

Distribution of urinary selenium and arsenic among pregnant women exposed to arsenic in drinking water

Inorganic arsenic (In-As) is a well-known toxicant and carcinogen found naturally in surface and groundwater around the world. Exposure can cause skin lesions, adverse reproductive outcomes, and cancer. There are two main pathways of arsenic (As) metabolism in humans: the reduction reactions, and the oxidative methylation reactions, where methyl groups are attached to As compounds to form monomethylarsenate (MMA) and dimethylarsenate (DMA). MMA, DMA, and In-As are excreted in urine. Urinary levels of another metalloid, selenium (Se), have recently been shown to be associated with increased As excretion and altered metabolite distribution. This study investigates this association, using data collected in a larger prospective study of arsenic and reproductive effects in Chile. This analysis included 93 pregnant women from Antofagasta. Data on demographic, behavioral, and other characteristics were obtained via interviews conducted by trained midwives, and spot urine samples were analyzed for As and Se concentration using inductively coupled plasma-mass spectrometry (ICP-MS). Urinary Se levels were found to be correlated with urinary As levels in bivariate analysis (r = 0.68, P < 0.01). Multiple linear regression analyses revealed that higher urinary Se levels were associated with increased urinary As excretion, increased %DMA, and decreased %In-As. The results of this study suggest that in populations exposed to arsenic, Se intake may be correlated with urinary As excretion, and may alter As methylation.     

同时测定水中砷和锑的氢化物发生-原子荧光光谱法

目的建立双道原子荧光光度计同时测定饮用水中砷和锑的方法,以提高工作效率。方法选择最佳的仪器条件,进行样品处理方法及酸度、硼氢化钾浓度、检出限、线性范围、精密度、加标回收率等研究。结果该方法线性关系:砷为0～80μg/L,锑为0～40μg/L。检出限:砷为0.087μg/L,锑为0.19μg/L。相对标准偏差:砷为1.93%～2.55%;锑为1.97%～3.02%。平均加标回收率:砷为95.7%;锑为96.5%。结论该方法操作简便,灵敏度高,快速,便于推广,适用于水中砷和锑的同时测定。     

Cancer incidence and high environmental arsenic concentrations in rural populations: Results of an ecological study

A number of ecological studies have suggested associations between arsenic in drinking water and increased rates of some cancers. To investigate associations in areas with high environmental arsenic concentrations, geographical areas with surface soil inorganic arsenic concentrations of >100 mg/kg and/ or drinking water arsenic concentrations >0.01 mg/l were selected and the relationship with cancer incidence explored. Standardised incidence rates (SIRs) for cancer were generated for 22 areas between 1982 and 1991 using Victorian Cancer Registry data and Victorian cancer rates as a baseline. SIRs were also generated for combined areas according to environmental exposure type, i.e. whether an area had high soil and/or high water arsenic concentrations. The SIRs for both males and females for the combined 22 areas were increased for all cancers 1.06 (95% confidence interval, CI; 1.03-1.09), prostate cancer 1.14 (1.05-1.23), kidney cancer 1.16 (0.98-1.37), melanoma 1.36 (1.24-1.48), chronic myeloid leukemia 1.54 (1.13-2.10) and breast cancer in females 1.10 (1.03-1.18). When stratifying into exposure categories, the SIR for prostate cancer was significant at 1.20 (1.06-1.36) for the high soil/high water category only. No significant dose- response relationship between drinking water and individual cancers was observed. Of the a priori cancers associated with environmental arsenic exposure, only prostate cancer incidence was significantly elevated in this study. This result was likely confounded by a number of factors and was limited by low power and exposure misclassification.     

杞县饮水型地方性氟中毒病区饮水氟砷含量与井深关系的探讨

目的探讨杞县农村饮水型地方性氟中毒病区分散式供水水氟、水砷含量与井深的关系,寻找适宜氟砷含量的饮水层,为地方病防治提供基础资料和科学依据。方法采集杞县氟中毒病区饮用井水样,测定水中氟、砷的浓度,分析浓度分布特点以及水氟、水砷、水井深度三者之间的关系。结果杞县地方性氟中毒病区水井深度在66 m以内,水氟含量与饮水井深度之间呈正相关关系,相关系数为0.108。水砷浓度与饮水井深度呈负相关关系,相关系数为-0.170。水氟含量与水砷含量之间无相关关系。结论饮水型地方性氟中毒病区水氟、水砷含量与井深之间有密切关系。水氟含量随饮水井深度的增加而增高;水砷含量随饮水井深度的增加而降低;而水氟、水砷浓度间不具有相关性。杞县饮水型地方性氟中毒病区饮水应避开现用水层,选择地表水或深层地下水。     

Maternal arsenic exposure and birth outcomes: A comprehensive review of the epidemiologic literature focused on drinking water

Inorganic arsenic (iAs) is a human toxicant to which populations may be exposed through consumption of geogenically contaminated groundwater. A growing body of experimental literature corroborates the reproductive toxicity of iAs; however, the results of human studies are inconsistent. Therefore, we conducted a comprehensive review of epidemiologic studies focused on drinking water iAs exposure and birth outcomes to assess the evidence for causality and to make recommendations for future study. We reviewed 18 English language papers assessing birth weight, gestational age, and birth size. Thirteen of the studies were conducted among populations with frequent exposure to high-level groundwater iAs contamination (>10 μg/L) and five studies were conducted in areas without recognized contamination. Most studies comprised small samples and used cross-sectional designs, often with ecologic exposure assessment strategies, although several large prospective investigations and studies with individual-level measurements were also reported. We conclude that: (1) the epidemiologic evidence for an increased risk of low birth weight (<2500 g) is insufficient, although there exists limited evidence for birth weight decreases; (2) the evidence for increased preterm delivery is insufficient; and, (3) there exists minimal evidence for decreased birth size. In further investigation of birth weight and size, we recommend incorporation of individual susceptibility measures using appropriate biomarkers, with collection timed to windows of vulnerability and speciated arsenic analysis, as well as consideration of populations exposed primarily to drinking water iAs contamination <10 μg/L. Given the large potential public health impact, additional, high quality epidemiologic studies are necessary to more definitively assess the risk.     

Seasonal variation of arsenic concentration in wells in Nevada

The issue of seasonal arsenic measurement variability poses consequences regarding the interpretation and frequency of well water measurements for both public health research and surveillance. In this study, we evaluated seasonal variability in arsenic concentration in 356 wells in western Nevada. River flow data obtained from US Geological Survey National Water Information System were used to classify seasons as wet or dry, and mean differences in arsenic well concentrations measured during these seasons were compared. Arsenic concentrations in these wells averaged 72.9 microg/L (range, non-detect to 3000 microg/L). The mean difference in arsenic concentrations between the wet and dry seasons was -3.3 microg/L (p = 0.78; average percent difference = 2.3%). Eighty wells (22%) had higher arsenic concentrations in the wet season, 75 wells (21%) had higher arsenic concentrations in the dry season and no difference was seen in 201 wells (56%). The mean differences in wells with arsenic levels of 0-10, 11-50, 51-200, > 200 microg/L were -1.4 microg/L(p=0.43), 9.2 microg/L(p=0.36), 15.1 microg/L(p=0.30), and -49.9 microg/L(p=0.59). In summary, although changes in arsenic concentrations were seen in some wells, clear trends in arsenic concentration over time were not associated with the wet and dry seasons. These findings provide evidence that, in our study area as a whole, little seasonal variability occurs in arsenic concentrations, and repeated assessments of arsenic concentrations based on season might add little value to the accuracy of health effects research or public health surveillance.     

氢化物发生-原子荧光光度法同时测定饮用水中砷和汞

目的:建立同时测定生活饮用水中砷和汞的氢化物发生-原子荧光光度法。方法:取一定量水样,在盐酸-硫脲-抗坏血酸混合介质中,放置一定时间后用原子荧光法同时测定。光电倍增管负高压均为290 V;汞灯电流为20 mA,砷灯电流为60 mA。结果:砷的方法检出限为0.0045μg/L,RSD为0.90%,加标回收率为100.6%～102.1%;汞的方法检出限为0.0048μg/L,RSD为2.1%,加标回收率为100.2%～103.0%。结论:氢化物发生-原子荧光光度法同时测定水中的砷和汞的精密度和准确度满足分析要求,具有快速、准确、灵敏等优点。     

杭锦后旗饮水氟砷暴露对儿童智力的影响

目的了解饮水氟、砷暴露对儿童智力的影响,为保护饮水型地方性氟砷中毒病区儿童健康提供科学依据。方法选择内蒙古杭锦后旗农村地区268名小学生作为研究对象,采集家庭饮用水样,测定氟、砷含量;采用联合型瑞文测试对研究对象进行智力测验,并针对家庭一般情况、饮水水源情况、儿童健康状况及其他智力影响因素等情况进行问卷调查。结果杭锦后旗儿童家庭饮用水氟含量为(1.24±0.74)mg/L,砷含量为(0.13±0.16)mg/L,均超过国家饮用水卫生标准限值。饮水砷含量≥0.05 mg/L的女生智商(95.9±14.2)显著低于饮水砷含量<0.05 mg/L的女生(101.3±13.2),而不同水砷浓度男生智商差异无统计学意义。饮水砷浓度≥0.05 mg/L对女生智商影响的调整OR值为2.81,而不同水氟浓度儿童智商差异无统计学意义。结论饮水氟、砷暴露不利于儿童的智力发育,对女生智力的影响较明显。     

农村饮水砷监测结果分析

目的 查明10省区和新疆生产建设兵团的饮水砷污染状况，为农村预防水性砷中毒和饮水改善规划的实施提供基础数据。方法 10省区和新疆生产建设兵团开展的“社区饮水砷监测系统”是在现有“全国农村饮水水质卫生监测网”基础上增加监测指标砷，通过合理布置监测点对饮水水源类型和供水方式等进行现场调查和监测饮水水质。结果 72个监测县共设726个监测点，除安徽、河南和山东没有检测出高砷水样(≥0．05mg/L)外，其他省区都检出了高砷水样；除安徽省没有氟化物含量超标水样外，其他省区均有氟化物含量超过一级标准(1．0mg／L)的水样。高砷高氟水样分布呈比较明显的地区性。调查覆盖人口2967．2万，其中饮用地面水的人口数为362．9万。占12．23％；饮用地下水人口为2604．3万，占87．77％。其中深井水饮用人口为1841．7万，占62．07％。调查覆盖人口中，饮用集中式供水人口为1114．1万，占调查覆盖人数的40．82％；分散式供水人口为1615．1万，占调查覆盖人口数的59．18％。结论 通过现场调查和抽样监测基本掌握了10省区和新疆生产建设兵团的饮水砷污染现状，对促进农村饮水改善有积极意义，同时也表明在这些地区进一步开展适时监测是非常必要的。     

深圳市水源水与出厂水10种金属元素浓度的比较

目的比较深圳市水源水、出厂水中10种金属元素浓度及变化。方法分别于2009年1月-2013年12月的丰水期(4-9月)和枯水期(1-2月、11-12月),采集深圳市9个市政水厂的水源水和出厂水水样,对砷(As)、镉(Cd)、六价铬(Cr6+)、铅(Pb)、汞(Hg)、硒(Se)、铁(Fe)、锰(Mn)、铜(Cu)、锌(Zn)的浓度进行检测。结果共采集水样90份,10种金属元素检测结果均合格。与水源水比较,出厂水中Cd、Cr6+、Pb、Hg、Se、Mn、Cu的浓度均较高,Fe的浓度较低,差异均有统计学意义(P<0.05);仅Zn的浓度无明显改变。与水源水比较,丰水期出厂水Cd、Cr6+、Hg的浓度较高,而Fe的浓度较低,差异均有统计学意义(P<0.05)。枯水期出厂水10种金属元素的浓度均高于水源水,差异均有统计学意义(P<0.05)。与水源水比较,以氯化消毒方式的出厂水中As、Cd、Cr6+、Pb、Hg、Se、Mn、Cu的浓度均较高,而Fe的浓度较低,差异均有统计学意义(P<0.05);Zn的浓度无明显差异。与水源水比较,以二氧化氯消毒方式的出厂水中As、Cd、Cr6+、Pb、Hg、Mn、Cu的浓度均较高,而Fe的浓度较低,差异均有统计学意义(P<0.05);Se、Zn的浓度均无明显差异。结论深圳市政水源水和出厂水中10种金属元素符合相应水质标准,部分金属元素出厂水浓度高于水源水。     

Impact of nitrates in drinking water on cancer mortality in Valencia,Spain

The concentrations of nitrates in public drinking water in the Mediterranean coastal province of Valencia are not only the highest in Spain but also in the whole of Europe. Intensive agricultural practices involve a traditional and growing use of nitrogen fertilizers. This and the terrain — poorly consolidated and porous in areas — favors the accumulation of nitrates in underground aquifers, thereby perhaps accounting for this contamination. The possible conversion of nitrates to nitrites under certain conditions of gastric achlorhydria, followed by their transformation to nitrosamines — substances known to be carcinogenic in experimental models — has led to a number of epidemiological studies of the possible relationship between high nitrate levels in public drinking water and mortality due to different cancers. The aim of the present study was to analyze the relationship between different levels of exposure to nitrates in the drinking water of the 258 municipalities in the province of Valencia and mortality due to cancer of the stomach, bladder, prostate and colon in this population. The cancer mortality rate was found to rise with increasing exposure to nitrates in the case of gastric cancer in both sexes, and in prostate cancer. These same results were obtained on calculating relative risk for the different age groups associated with the consumption of drinking water containing different levels of nitrates. Thus, in populations with nitrate concentrations in excess of 50 mg/1, relative risk for gastric cancer in the 55–75 years age group was 1.91 and 1.81 for males and females, respectively (p<0.05). In the case of prostate cancer elevated relative risks were also encountered: 1.86 and 1.80 for the 55–75 and over 75 years age groups, respectively.     

Spontaneous pregnancy loss in humans and exposure to arsenic in drinking water

Maternal exposure to high concentrations of inorganic arsenic (iAs) in naturally contaminated drinking groundwater sources has been associated with an increased risk for the spontaneous loss of clinically recognized pregnancies in several epidemiologic studies. Whereas a large worldwide population depends on drinking groundwater sources with high levels of iAs contamination, in quantities exceeding 10 parts per billion (ppb), an even larger population is likely to be exposed to mild-moderate drinking groundwater iAs contamination, in quantities <10ppb. Only a single epidemiologic study to date has considered spontaneous pregnancy loss in association with consumption of drinking water with mild-moderate iAs contamination; the vast majority of published studies of spontaneous loss addressed populations with substantial exposure. The aim of this review is to evaluate the published literature to assess the plausibility for a causal association between exposure to iAs-contaminated drinking water and the spontaneous loss of clinically recognized pregnancy. In spite of numerous methodologic limitations resulting from circumstance or design, a consistent pattern of increased risk for loss is suggested by the epidemiologic literature. Moreover, these study results are corroborated by a large number of experimental studies, albeit usually conducted at concentrations exceeding that to which humans are exposed via contaminated drinking water. In this review, we discuss sources of human iAs exposure, highlight several experimental studies pertinent to a possible causal link between iAs and spontaneous pregnancy loss in humans, and provide a critical review of published epidemiologic studies of pregnancy loss and drinking water iAs exposures, and their limitations. Based on a review of the published literature, we recommend the future conduct of a two-stage comprehensive prospective study of low-moderate iAs drinking water exposure and spontaneous pregnancy loss.     

Arsenic in public water supplies and cardiovascular mortality in Spain

Background

High-chronic arsenic exposure in drinking water is associated with increased cardiovascular disease risk. At low-chronic levels, as those present in Spain, evidence is scarce. In this ecological study, we evaluated the association of municipal drinking water arsenic concentrations during the period 1998−2002 with cardiovascular mortality in the population of Spain.

Methods

Arsenic concentrations in drinking water were available for 1721 municipalities, covering 24.8 million people. Standardized mortality ratios (SMRs) for cardiovascular (361,750 deaths), coronary (113,000 deaths), and cerebrovascular (103,590 deaths) disease were analyzed for the period 1999−2003. Two-level hierarchical Poisson models were used to evaluate the association of municipal drinking water arsenic concentrations with mortality adjusting for social determinants, cardiovascular risk factors, diet, and water characteristics at municipal or provincial level in 651 municipalities (200,376 cardiovascular deaths) with complete covariate information.

Results

Mean municipal drinking water arsenic concentrations ranged from <1 to 118 μg/L. Compared to the overall Spanish population, sex- and age-adjusted mortality rates for cardiovascular (SMR 1.10), coronary (SMR 1.18), and cerebrovascular (SMR 1.04) disease were increased in municipalities with arsenic concentrations in drinking water >10 μg/L. Compared to municipalities with arsenic concentrations <1 μg/L, fully adjusted cardiovascular mortality rates were increased by 2.2% (−0.9% to 5.5%) and 2.6% (−2.0% to 7.5%) in municipalities with arsenic concentrations between 1−10 and>10 μg/L, respectively (P-value for trend 0.032). The corresponding figures were 5.2% (0.8% to 9.8%) and 1.5% (−4.5% to 7.9%) for coronary heart disease mortality, and 0.3% (−4.1% to 4.9%) and 1.7% (−4.9% to 8.8%) for cerebrovascular disease mortality.

Conclusions

In this ecological study, elevated low-to-moderate arsenic concentrations in drinking water were associated with increased cardiovascular mortality at the municipal level. Prospective cohort studies with individual measures of arsenic exposure, standardized cardiovascular outcomes, and adequate adjustment for confounders are needed to confirm these ecological findings. Our study, however, reinforces the need to implement arsenic remediation treatments in water supply systems above the World Health Organization safety standard of 10 μg/L.     

Arsenic in drinking water and lung cancer: a systematic review

Exposure to inorganic arsenic via drinking water is a growing public health concern. We conducted a systematic review of the literature examining the association between arsenic in drinking water and the risk of lung cancer in humans. Towards this aim, we searched electronic databases for articles published through April 2006. Nine ecological studies, two case-control studies, and six cohort studies were identified. The majority of the studies were conducted in areas of high arsenic exposure (100 μg/L) such as southwestern Taiwan, the Niigata Prefecture, Japan, and Northern Chile. Most of the studies reported markedly higher risks of lung cancer mortality or incidence in high arsenic areas compared to the general population or a low arsenic exposed reference group. The quality assessment showed that, among the studies identified, only four assessed arsenic exposure at the individual level. Further, only one of the ecological studies presented results adjusted for potential confounders other than age; of the cohort and case-control studies, only one-half adjusted for cigarette smoking status in the analysis. Despite these methodologic limitations, the consistent observation of strong, statistically significant associations from different study designs carried out in different regions provide support for a causal association between ingesting drinking water with high concentrations of arsenic and lung cancer. The lung cancer risk at lower exposure concentrations remains uncertain.     

湖北省农村饮用水与环境卫生现状调查

目的了解湖北省农村饮用水与环境卫生现状。方法采取按比例分层随机方式选取20个县、每个县随机选择10个行政村作为调查对象,开展现场调查和水样采样检测。结果调查县农村居民使用集中式供水人口占26．74％,分散式供水占73．26％,饮用水水质总体合格率为40％,其中集中式供水水质合格率为50．60％,分散式供水水质合格率为32．20％。卫生厕所占总户厕的26．17％;生活垃圾、生产垃圾分别占垃圾总量的19．21％和80．79％,生活污水随意排放占60．70％。结论农村饮水供水方式和饮用水水质亟待改善,卫生厕所普及率低,垃圾及污水的收集和处理环境卫生状况不容乐观。     

Effectiveness of arsenic mitigation program in Bangladesh--relationship between arsenic concentrations in well water and urine

BACKGROUND: Arsenic in drinking water remains a major public problem in Bangladesh, although arsenic mitigation programs began there a decade ago. The purpose of this study was to examine the effectiveness of this program by determining the relationship between current arsenic levels in well water and the high level of urinary arsenic excretion. METHODS: A community-based cross-sectional study was conducted in the Pabna district of Bangladesh between May and July 2005. We included 174 married couples and collected their drinking water from 138 wells. The allowable limit for arsenic in drinking water is 50 microg/L in Bangladesh, while the normal level of urinary arsenic is < or =40 microg x 1.5 L(-1) x day(-1) by Dhaka Community Hospital. RESULTS: Of 348 subjects, 304 exceeded the urinary arsenic level of 40 microg x 1.5 L(-1) x day(-1). Of all wells, 44.2% had arsenic levels >50 microg/L. Multiple-adjusted odds ratios of urinary arsenic level >40 microg x 1.5 L(-1) x day(-1) were 8.90 (95% CI: 3.31-23.93) for the arsenic level in well water of 11-50 microg/L, and 53.07 (11.91-236.46) for that of 51-332 microg/L, compared with < or =10 microg/L. When the Bangladeshi standard arsenic level in drinking water of 50 microg/L was used, the sensitivity in detecting subjects with a urinary arsenic level >40 microg x 1.5 L(-1) x day(-1) was 50%, although when the World Health Organization (WHO) guideline value of 10 microg/L was used, it was 76.3%. CONCLUSIONS: Green marked wells, which the Bangladesh government regards as safe, are not always safe. The mitigation programs should use the WHO guideline arsenic level to determine the safety of well water for drinking.