The relationship between arsenic in drinking water and cancer can best be sumarized by quoting from a June 29, 2000 United States Senate Subcommittee hearing on Fisheries, Wildlife and Drinking Water. Quoting:

Erik D. Olson
Natural Resources Defense Council

The National Academy of Sciences, in a report issued in 1999, recognized that arsenic in tap water poses a significant public health risk in the United States, and that EPA's outdated tap water standard for arsenic, which was set in 1942, "does not achieve EPA's goal for public health protection

The Academy concluded that drinking water containing arsenic at the 50 parts per billion (ppb) level allowed by the outdated current standard "could easily" pose a total cancer risk of 1 in 100 about 100 times higher than EPA would ever allow for tap water under other rules.

The Academy discussed a litany of other adverse non-cancer health effects from arsenic in tap water, including cardiovascular effects, nervous system problems, skin lesions, possible reproductive harms and other effects. Several peer-reviewed, published studies completed in the year since the Academy's report have reinforced the conclusion that a much lower standard for arsenic in tap water is needed to protect public.

Three studies published in the July 2000 issue of the National Institutes of Health's Journal, Environmental Health Perspectives, found that arsenic in drinking water is linked to skin problems and other adverse health effects even in well-nourished populations. Additionally, the studies link the presence of arsenic in tap water to certain reproductive problems in exposed women, and increased cancer risks.

Dr. Michael J. Kosnett
Associate Clinical Professor of Medicine Division of Clinical Pharmacology and Toxicology
University of Colorado Health Sciences Center Denver, Colorado
on Behalf of the National Research Council's Subcommittee on Arsenic in Drinking Water

A wide variety of adverse health effects, including skin and internal cancers and cardiovascular and neurological effects, have been attributed to chronic arsenic exposure, primarily from drinking water.

The subcommittee concludes that there is sufficient evidence from human epidemiological studies.. that chronic ingestion of arsenic causes bladder and lung cancer, as well as skin cancer.