Inorganic Arsenic in Drinking Water: An Evolving Public Health Concern

In recent years, ingestion of inorganic arsenic from drinking water has emerged as an important scientific issue and public health concern. The International Agency for Research on Cancer has identified sufficient evidence in humans that inorganic arsenic causes lung, bladder, and nonmelanoma skin cancers ( 1 ) (summary at http://monographs.iarc.fr/ ). Reports by expert committees have suggested associations with several other cancer and noncancer outcomes ( 2–4 ). As a result, the US Environmental Protection Agency lowered the maximum contaminant level for arsenic in drinking water supplied by community water systems from 50 μg/L, a level set in 1942, to 10 μg/L, effective from January 2006. The reduction will necessitate changes to water systems serving approximately 13 million people ( http://www.epa.gov/safewater/arsenic/compliance.html ). The World Health Organization has similarly recommended 10 μg/L for arsenic in water as a “guideline value” for setting national standards ( http://www.who.int/mediacentre/factsheets/fs210/en/index.html ). Substantial numbers of people worldwide are exposed to elevated concentrations of arsenic. An estimated 25 million people in Bangladesh (19% of the population) and 6 million people in West Bengal, India (8% of the population), consume water with arsenic exceeding 50 μg/L ( 5 ), with perhaps twice these numbers in these countries consuming water with arsenic levels exceeding 10 μg/L. High levels of inorganic arsenic levels are found in drinking water in many other parts of the world, including areas of Argentina (county means ranged to 178 μg/L) ( 6 ), the Inner Mongolia and Xinjiang autonomous regions in China (levels in excess of 600 μg/L) ( 7 ), Finland (levels were generally low but ranged to 64 μg/L) ( 8 ), northern Mexico (ranges in exposed areas to 160–740 μg/L) ( 9 ), and the United States (with some areas in California, Nevada, Alaska, Michigan, New England, New Mexico, and Utah exceeding 50 μg/L) (see US Geological Survey map of 31350 ground water measurements at http://co.water.usgs.gov/trace/pubs/arsenic_fig1.html ). Drinking water arsenic levels in excess of 150 μg/L also occur in Nepal ( 10 ), Thailand ( 11 ), Vietnam ( 12 ), Hungary ( 13 ), Ghana ( 14 ), and elsewhere ( 15 ). Although arsenic contamination of water supplies arises mainly from natural sources, human activities such as mining and ore processing may also contribute to elevated arsenic levels in some areas.