By Gilbert Ross, M.D., Kenneth G. Brown, Ph.D.
Posted: Friday, March 1, 2002
REPORT
Publication Date: March 1, 2002
Executive Summary
There is considerable controversy over whether chronic exposure to arsenic in drinking water at concentrations found in the United States poses a health risk. The current maximum contaminant level (MCL), 50µg/L [50µgm/L=50 parts per billion, or ppb]*, has been in place, at least as an interim limit, since 1942. A 1999 report of the National Research Council (NRC 1999), commissioned by the U.S. Environmental Protection Agency (EPA), concludes that the MCL does not achieve EPA's goal for public-health protection and advised downward revision as promptly as possible (NRC 1999). Subsequently, the EPA proposed an MCL of 5 µg/L, changed it to a final rule of 10µg/L, and then, with the change of administration, reopened the topic to consider 3µg/L, 5µg/L, 10µg/L, and 20µg/L. 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 U.S. Some background is included on how these issues arose, as well as a review of the 1999 NRC report, 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 µg/L 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 multi-systemic, 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 MCL of 50 µg/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 report, the American Council on Science and Health finds that the limitations of the epidemiological data available and the state-of-the-science on the mode-of-action of arsenic toxicity, including cancer, are inadequate to support the conclusion that there are adverse health effects in the United States from arsenic in drinking water below the current limit of 50 µg/L.
* We use µg/L in this document, although As concentrations and MCL are popularly spoken of in ppb.
Related Links
Arsenic, Drinking Water, and Health
