Water Quality Standards

Arsenic is widely distributed throughout the earth's crust and is used commercially, primarily in alloying agents. It is introduced into water through the dissolution of minerals and ores, from industrial effluents, and from atmospheric deposition; concentrations in ground water in some areas are sometimes elevated as a result of erosion from natural sources. The average daily intake of inorganic arsenic in water is estimated to be similar to that from food; intake from air is negligible.

Inorganic arsenic is a documented human carcinogen and has been classified by IARC in Group 1. A relatively high incidence of skin and possibly other cancers that increase with dose and age has been observed in populations ingesting water containing high concentrations of arsenic.

Arsenic has not been shown to be carcinogenic in the limited bioassays in animal species that are available, but it has given positive results in studies designed to assess the potential for tumour promotion. Arsenic has not been shown to be mutagenic in bacterial and mammalian assays, although it has been shown to induce chromosomal aberrations in a variety of cultured cell types, including human cells; such effects have not been observed in vivo.