Overview of the Nature, Extent, Health Risks, and Treatment of Metal-affected Drinking Water in Bangladesh

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Conclusions and Recommendations

This study suggests the most significant health risk from drinking Bangladesh’s tubewell water is chronic arsenic poisoning. Over 50,000,000 Bangladeshis are drinking water with unsafe levels of arsenic.
The severity of chronic arsenic poisoning in Bangladesh might be magnified by exposure to antimony. In particular, the toxicity of arsenic is modulated by antimony. Our results show that 97% of the drinking water samples with detectable concentrations of arsenic also had detectable concentrations of antimony.
Conversely, the severity of chronic arsenic poisoning in Bangladesh might be magnified by a lack of selenium, a lack of zinc, or a lack of both selenium and zinc. In particular, selenium is an essential element that prevents the cytotoxic effects of arsenic. Our results show that 92% of the drinking water samples with detectable concentrations of arsenic did not have detectable concentrations of selenium. Similarly, zinc is an essential element that promotes the repair of tissues damaged by arsenic. Our results show that 18% of the drinking water samples with detectable concentrations of arsenic did not have detectable concentrations of zinc. Moreover, Bangladesh’s agricultural soils might be selenium deficient and are often zinc deficient; therefore, it is possible that the lack of these essential nutritive elements in drinking water and possibly food may cause a magnification of arsenic toxicity.
The major sources of arsenic in Bangladesh’s groundwater might be the dissolution of non-pyrite minerals in a reducing environment, and the anion exchange of sorbed arsenate or sorbed arsenite.
This study does not support the hypothesis that arsenic is released from a pyrite source during oxidation; therefore, it does not begin to support the unproven strategy of restricting irrigation in famine-prone Bangladesh to prevent the release of arsenic from pyrite into groundwater.
The first of 3 strategies to supply Bangladesh with drinking water that has safe levels of arsenic is to identify, use, and monitor existing tubewells that have less than 0.05 mg of As/L. This strategy is the most promising because it can rapidly and inexpensively provide drinking water with safe levels of arsenic to approximately 85% of this 120,000,000-person country.
The second of these strategies is to provide an alternative drinking water source by drilling deeper tubewells. This strategy is moderately promising because the drinking water it yields often has arsenic concentrations greater than the 0.05 mg/L national standard.
The last of these strategies is groundwater treatment for arsenic removal. Appropriate treatment systems should be effective, inexpensive, and easily operated by even an illiterate person.
In addition to arsenic, proportions of Bangladesh’s tubewell water contain unsafe levels of manganese, lead, nickel, or chromium. Therefore, Bangladesh’s tubewell water should be routinely monitored for these and possibly other toxins.
The contour maps of arsenic concentration in groundwater suggests this toxin extends beyond Bangladesh’s borders into West Bengal, Assam, Meghalaya, and Tripura (the 4 Indian States that border Bangladesh). Unsafe levels of arsenic have been identified in groundwater from West Bengal; however, we are unaware of any systematic survey of other toxins in West Bengal’s groundwater. We are also unaware of any systematic survey of tubewell water quality in Assam, Meghalaya, or Tripura. Therefore, the groundwater used for drinking in West Bengal, Assam, Meghalaya, and Tripura should be tested to ensure it has safe levels of arsenic, manganese, lead, nickel, chromium, and possibly other toxins.
Arsenic readily leaches from many of Bangladesh’s surface soils and can be uptaken by crops. Therefore, the ingestion of domestically grown foods should be evaluated as a human exposure pathway for arsenic, manganese, lead, nickel, chromium, and possibly other toxins.

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