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The major sources of arsenic in drinking water are erosion of natural deposits, runoff from orchards, and runoff from glass and electronics production wastes.
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Arsenic is a semi-metal element in the periodic table. It is odorless and tasteless. It enters drinking water supplies from natural deposits in the earth or from agricultural and industrial practices.
Approximately 90% of industrial arsenic in the U.S. is currently used as a wood preservative, but arsenic is also used in the following:
Agricultural applications, mining, and smelting also contribute to arsenic releases in the environment.
Some people who drink water containing arsenic well in excess of the maximum contaminant level (MCL) for many years could experience skin damage or problems with their circulatory system, and may have an increased risk of getting cancer. This health effects language is not intended to catalog all possible health effects for arsenic. Rather, it is intended to inform consumers of some of the possible health effects associated with epichlorohydrin in drinking water when the MCLG for arsenic is zero.
The Environmental Protection Agency has set this level of protection based on the best available science to prevent potential health problems. Based on the MCLG, the Environmental Protection Agency has set an enforceable regulation for arsenic, called a MCL, at 0.010 milligrams per liter or 10 ppb. MCLs are set as close to the health goals as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies.
The Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring Final Rule, the regulation for arsenic, became effective in 2002. The Safe Drinking Water Act requires the Environmental Protection Agency to periodically review and revise contaminants, if appropriate, based on new scientific data. The regulation for arsenic will be included in a future review cycle.