The highest concentrations of arsenic in food are found in marine products, but these are in the organic form, usually arsenobetaine, which is not toxic. Various sources of exposure to inorganic arsenic, as arsenates or arsenites, exist. Occupational exposure to inorganic forms of arsenic occurs primarily by inhalation. Arsenic in drinking water is predominantly the trivalent and pentavalent forms as salts (EPA, 1988). Arsenic is also being used in the treatment of leukemias (Konig et al., 1997; Look, 1998).
The median intake of arsenic by men and by women was approximately 2.0 to 2.9 μg/day and 1.7 to 2.1 μg/day, respectively (Appendix Table E-2). Adams and coworkers (1994) reported lower intakes for adults (23 to 58 μg/day) from 1982 to 1991. The level of inorganic arsenic in water was about 2 μg/L (ATSDR, 1998). The drinking water for about 98 percent of the U.S. population was below 10 μg/L (Chappell et al., 1997). The U.S. Environmental Protection Agency (EPA) has a maximum contaminant level (MCL) of 50 μg/L for water supplies in the United States (EPA, 1975). However, the agency recently proposed a much lower MCL of 5 μg/ L for arsenic in drinking water and is seeking comments on MCLs ranging from 3 to 20 μg/L (EPA, 2000). The EPA expects to promulgate a new, lower MCL in the near future. The average arsenic content of mineral drinking water in European countries is 21 μg/L (Zielhuis and Wibomo, 1984).
Although no UL was set for arsenic, there is no justification for adding arsenic to food and there may be a risk of adverse effects with consumption of organic arsenic in food or with intake of inorganic arsenic in water supplies at the current MCL of 50 μg/L in the United States. Substantial numbers of individuals in North America, however, are exposed to arsenic levels exceeding the MCL (Chappell et al., 1997; Grantham and Jones, 1977; Kreiss et al., 1983). Inhalation exposure occurs in occupational settings such as smelters and chemical plants, where the predominant form of airborne arsenic is arsenic trioxide dust (ATSDR, 1998).
A better understanding of species differences in biotransformation of arsenic and toxicity.