ABSTRACT
A physiologic role of arsenic, affecting the methionine metabolism in animals, characterizes this element as essential for rats, hamsters, goats, minipigs and chicken (NRC 1999; Thornton 1999; Uthus 1990). Arsenic supplementation seems to have a growth-stimulating effect at very high doses in these animals (NRC 1999). However, arsenic does not fulfill one of the main criteria for being essential in humans, that is, “the reduction of exposure to the element below a certain limit must result consistently and reproducibly in an impairment of physiologically important functions, and restitution of the element under otherwise identical conditions might prevent the impairment” (NRC 1999). A controversy still exists regarding its function in human metabolism, although Mayer et al. (1993) suggest that arsenic deficiency might contribute to the increased risk of death in hemodialysis patients. However, arsenic has not been found to be required for any essential human biochemical process (NRC 1999). Natural As concentrations in non-polluted environments are probably sufficient to provide any supposedly nutritional need by humans (c 1, 13; Thornton 1999). Whether arsenic is essential was not adequately tested in humans so far, and the metabolic necessity of the element is unknown. The latter is being considered to be <0.01 mg day−1, based on an average body content of 7 mg (0.1 mg As kg−1) found in a regular adult of 70 kg. A non-exposed person can have at least 1 mg As kg−1 in the hair (Emsley 2005; c 1: Table 1.6; c 14).
