ABSTRACT

A nonessential toxic element, arsenic is a metalloid that exists in four valence states, (-3, 0, 3, and 5), with the principal ones being arsenite (As3) and arsenate (As5), occurring in trace amounts in both organic and inorganic compounds in the environment. Toxicity of the element is dependent on its chemical form. The inorganic compounds are of particular health concern as they are more acutely and subacutely toxic than the environmentally occurring organic ones (e.g., dimethylarsinate), and arsenites have been shown to be more toxic than arsenates (1). Specifically, a comparison of the ED50 values of the two oxidation states (as sodium arsenite and arsenate) in mouse embryos showed that arsenite was about three times more potent than arsenate with respect to both malformations and lethality (2). Present in all living organisms, As is found widely distributed in most human tissues. In the normal human body, total amounts of arsenic range from 14 to 21 mg, and individual tissues contain from 0.01 ppm (liver and bone) to 4 ppm (nails) (3).