Mortality for certain diseases in areas with high levels of arsenic in drinking water

Arsenic, drinking water, and health: a position paper of the American Council on Science and Health

The purpose of this American Council on Science and Health report is to review issues and sources of uncertainty affecting assessment of potential health risks related to drinking water in the United States. Some background is included on how these issues arose, as is a review of the 1999 National Research Council report (with references to an updated version), to formulate a position based on the current science concerning how much of a risk of adverse health effects actually exists from arsenic in drinking water in the United States. ACSH concludes that there is clear evidence that chronic exposure to inorganic arsenic at concentrations of at least several hundred micrograms per liter may cause: (1) cancer of skin, bladder, lung (and possibly several other internal organs, including kidney, liver, and prostate), and (2) noncancer effects, including classic cutaneous manifestations that are distinctive and characteristic of chronic arsenic poisoning (diffuse or spotted hyperpigmentation and palmar-plantar hyperkeratoses). Noncancer effects may be multisystemic, with some evidence of peripheral vascular, cardiovascular, and cerebrovascular disease, diabetes, and adverse reproductive outcomes. Further study is needed to know if beneficial effects of arsenic in animal studies apply to humans. ACSH concludes that there is little, if any, evidence of a detrimental health effect in humans from inorganic arsenic in drinking water at the current maximum contaminant level (MCL) of 50 microg/L or below, either in the United States or elsewhere. As noted in the 1999 NRC report, "No human studies of sufficient statistical power or scope have examined whether consumption of arsenic in drinking water at the current MCL results in an increased incidence of cancer or noncancer effects" (NRC, 1999, p. 7). Based on our review, described in this article, ACSH finds that the limitations of the epidemiological data available and the state-of-the-science on the mode-of-action of arsenic toxicity, including can cer, are inadequate to support the conclusion that there are adverse health effects in the United States from arsenic in drinking water at or below the limit of 50 microg/L.

Epidemiologic evidence of diabetogenic effect of arsenic

It is well documented that arsenic can lead to skin lesions, atherosclerotic diseases and cancers. The association between arsenic exposure and diabetes mellitus is a relatively new finding. Up to now, there are six epidemiologic reports linking diabetes mellitus with arsenic exposure from environmental and occupational sources. Two reports in Taiwan carried out in the blackfoot disease-hyperendemic villages, one cross-sectional and one prospective follow-up of the same cohort, indicate that arsenic exposure from drinking artesian well water is associated with prevalence and incidence of diabetes mellitus in a dose-responsive pattern. The observation of the relation between arsenic exposure and diabetes mellitus is further supported by studies carried out in Sweden and Bangladesh. In Sweden, case-control analyses of death records of copper smelters and glass workers revealed a trend of increasing diabetes mellitus with increasing arsenic exposure from inhalation. In Bangladesh, prevalence of diabetes mellitus among arsenic-exposed subjects with keratosis was about five times higher than unexposed subjects. Increasing trends of diabetes mellitus with indices of arsenic exposure in drinking water seems to be independent of the presence of skin lesions associated with arsenic exposure. Although these studies consistently show an association between arsenic exposure and diabetes mellitus, the weak study designs of cross-sectional or case-control, the use of glucosuria or diabetes death as diagnostic criteria and the lack of adjustment for possible confounders in some studies, are major limitations that may reduce the strength of the evidence.

The MRP2/cMOAT transporter and arsenic-glutathione complex formation are required for biliary excretion of arsenic

Worldwide, millions of people are exposed to arsenic in drinking water that exceeds the World Health Organization standard of 10 microg/liter by as much as 50-300-fold, yet little is known about the molecular basis for arsenic excretion. Here we show that transport of arsenic into bile depends on the MRP2/cMOAT transporter and that glutathione is obligatory for such transport. Using reversed phase liquid chromatography/mass spectrometry, we demonstrate that two arsenic-glutathione complexes not previously identified in vivo, arsenic triglutathione and methylarsenic diglutathione, account for most of the arsenic in the bile. The structure of the compounds was also confirmed by nuclear magnetic resonance spectroscopy. Our findings may help explain the increased susceptibility of malnourished human populations to arsenic.