[show abstract][hide abstract] ABSTRACT: Since 1996, 52,202 water samples from hand tubewells were analyzed for arsenic (As) by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) from all 64 districts of Bangladesh; 27.2% and 42.1% of the tubewells had As above 50 and 10 μg/l, respectively; 7.5% contained As above 300 μg/l, the concentration predicting overt arsenical skin lesions. The groundwater of 50 districts contained As above the Bangladesh standard for As in drinking water (50 μg/l), and 59 districts had As above the WHO guideline value (10 μg/l). Water analyses from the four principal geomorphological regions of Bangladesh showed that hand tubewells of the Tableland and Hill tract regions are primarily free from As contamination, while the Flood plain and Deltaic region, including the Coastal region, are highly As-contaminated. Arsenic concentration was usually observed to decrease with increasing tubewell depth; however, 16% of tubewells deeper than 100 m, which is often considered to be a safe depth, contained As above 50 μg/l. In tubewells deeper than 350 m, As >50 μg/l has not been found. The estimated number of tubewells in 50 As-affected districts was 4.3 million. Based on the analysis of 52,202 hand tubewell water samples during the last 14 years, we estimate that around 36 million and 22 million people could be drinking As-contaminated water above 10 and 50 μg/l, respectively. However for roughly the last 5 years due to mitigation efforts by the government, non-governmental organizations and international aid agencies, many individuals living in these contaminated areas have been drinking As-safe water. From 50 contaminated districts with tubewell As concentrations >50 μg/l, 52% of sampled hand tubewells contained As <10 μg/l, and these tubewells could be utilized immediately as a source of safe water in these affected regions provided regular monitoring for temporal variation in As concentration. Even in the As-affected Flood plain, sampled tubewells from 22 thanas in 4 districts were almost entirely As-safe. In Bangladesh and West Bengal, India the crisis is not having too little water to satisfy our needs, it is the challenge of managing available water resources. The development of community-specific safe water sources coupled with local participation and education are required to slow the current effects of widespread As poisoning and to prevent this disaster from continuing to plague individuals in the future.
Water Research 11/2010; 44(19):5789-802. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Urinary arsenic is generally considered as the most reliable indicator of recent exposure to inorganic arsenic and is used as the main bio-marker of exposure. However, due to the different toxicity of arsenic compounds, speciation of arsenic in urine is generally considered to be more convenient for health risk assessment than measuring total arsenic concentration. Additionally, it can give valuable information about the metabolism of arsenic species within the body. In our study, for exposed group--42 urine samples were collected from Datterhat (South) village of Madaripur district, Bangladesh and an average arsenic concentration in their drinking water was 376 microg/L (range 118 to 620 microg/L). For control group, 27 urine samples were collected from a non-affected district, Badhadamil village of Medinipur district, West Bengal, India, where arsenic concentration in their drinking water is below 3 microg/L. The arsenic species in the urine were separated and quantified by using HPLC-ICP-MS. The sum of inorganic arsenic and its metabolites was also determined by FI-HG-AAS. Results indicate that average total urinary arsenic metabolites in children's urine is higher than adults and total arsenic excretion per kg body weight is also higher for children than adults. For arsenic species between adults and children, it has been observed that inorganic arsenic (In-As) in average is 2.36% and MMA is 6.55% lower for children than adults while DMA is 8.91% (average) higher in children than adults. The efficiency of the methylation process is also assessed by the ratio between urinary concentration of putative product and putative substrate of the arsenic metabolic pathway. Higher values mean higher methylation capacity. Results show the values of the MMA/In-As ratio for adults and children are 0.93 and 0.74 respectively. These results indicate that first reaction of the metabolic pathway is more active in adults than children. But a significant increase in the values of the DMA/MMA ratio in children than adults of exposed group (8.15 vs. 4.11 respectively) indicates 2nd methylation step is more active in children than adults. It has also been shown that the distribution of the values of DMA/MMA ratio to exposed group decrease with increasing age (2nd methylation process). Thus from these results we may infer that children retain less arsenic in their body than adults. This may also explain why children do not show skin lesions compared to adults when both are drinking same contaminated water.
Journal of Environmental Science and Health Part A 02/2003; 38(1):87-113. · 1.25 Impact Factor
[show abstract][hide abstract] ABSTRACT: The exposure of millions to arsenic contaminated water from hand tube wells is a major concern in many Asiatic countries. Field kits are currently used to classify tube wells as delivering arsenic below 50 microg/L (the recommended limit in developing countries) as safe, painted green or above 50 microg/L, unsafe and painted red. More than 1.3 million tube wells in Bangladesh alone have been tested by field kits. A few million U.S. dollars have already been spent and millions are waiting for the ongoing projects. However, the reliability of the data generated through field kits is now being questioned. Samples from 290 wells were tested by field kits and by a reliable laboratory technique to ascertain the reliability of field kits. False negatives were as high as 68% and false positives up to 35%. A statistical analysis of data from 240 and 394 other wells yielded similar rates. We then analyzed 2866 samples from previously labeled wells and found 44.9% mislabeling in the lower range (<50 microg/L) although mislabeling was considerably reduced in the higher range. Variation of analytical results due to analysts and replicates were pointed out adopting analysis of variance (ANOVA) technique. Millions of dollars are being spent without scientific validation of the field kit method. Facts and figures demand improved, environmentally friendly laboratory techniques to produce reliable data.
Environmental Science and Technology 12/2002; 36(24):5385-94. · 5.26 Impact Factor