How does overexposure to arsenic occur

From the Editors of E/The Environmental Magazine

How does overexposure to arsenic occur, and what are its health hazards?]

—Cheryl Timm, Santa Fe, NM

Arsenic is a naturally occurring substance in many rocks, and low levels of arsenic can be found in groundwater as a result of the erosion of rock minerals. However, high levels of arsenic in drinking water are often associated with industrial pollutants, including alloying agents and wood preservatives, which are either disposed of directly into water bodies, or at waste disposal sites where they can leach into groundwater. Burning gas and oil can also release arsenic into the environment, but contaminated water poses a greater health risk. According to the World Health Organization (WHO), only minimal amounts of arsenic are absorbed through the skin, so drinking tainted water poses more of a health risk than bathing or laundering with arsenic-contaminated water.

Long-term exposure to arsenic can cause cancer of the lungs, kidney and bladder. It also results in maladies of the skin and changes in pigmentation. WHO reports that “increased risks of cancer and skin lesions have been observed in drinking water arsenic concentrations of less than 0.05 milligrams per liter, or 50 parts per billion (ppb).” A 2001 study done by the National Academy of Sciences found that people who consume water containing 0.003 milligrams per liter, or three ppb, of arsenic daily have about a one in 1,000 increased risk of developing bladder or lung cancer during their lifetime. At five ppb, the risk is about 1.5 in 1,000; at 10 ppb, it is greater than three in 1,000; and at 20 ppb, it is close to seven in 1,000. Increased public awareness of new findings on the human health risks of arsenic helped to put pressure on the U.S. Environmental Protection Agency (EPA) to consider more conservative standards for arsenic in drinking water. The EPA received more than 57,000 comments from Americans calling for a three part per billion standard, according to the Natural Resources Defense Council.

To ensure drinking water is free of threatening levels of arsenic, the WHO and the European Union have recommended or established a 10 ppb standard. In order to comply with 1996 Safe Drinking Water Act Amendments that require new research on the effects of arsenic and new standards in the U.S., the Clinton administration pushed for a regulation that reduced allowable levels of arsenic from the 1940’s standard of 50 parts per billion to 10 parts per billion. After some delay, the Bush administration put its stamp of approval on this new standard, which public drinking water systems have to comply with by 2006.

CONTACTS: World Health Organization, Avenue Appia 20, 1211 Geneva, 27 Switzerland, (+00 41 22) 791-21-11,; National Academies Press, 500 Fifth Street, NW Lockbox 285, Washington, DC 20055, (800) 624-6242, (Arsenic in Drinking Water: 2001 Update); U.S. Environmental Protection Agency Office of Groundwater and Drinking Water, (800) 426-4791 (Safe Drinking Water Hotline),