7. Effects on Laboratory Mammals and in Vitro Test Systems

The acute oral LD50s of several inorganic arsenicals are listed in Table 23. Trivalent inorganic arsenic is generally more toxic than pentavalent inorganic arsenic. The oral LD50 of As2O3 (As2O3), a trivalent arsenical, administered to three strains of mice, ranges from 26 to 36 mg As/kg body weight (Harrison et al., 1958; Kaise et al., 1985). Because of the low solubility of As2O3 in water, Harrison et al. (1958) heated the solution to dissolve the As2O3 and there is a question regarding the arsenic valence state because of this treatment. However, Kaise et al. (1985) reported a similar LD50 in their study with As2O3, but using a younger mouse. They did not indicate whether the solution was heated. The LD50 of As2O3 administered in food was 145 mg As/kg (Harrison et al., 1958). The symptoms observed from As2O3 intoxication include convulsions, retching and haemorrhaging in the intestinal tract. The severity of the symptoms appears to be related to the purity of As2O3: pure As2O3 has less severe side-effects than the commercial-grade compound, but greater lethality (Harrison et al., 1958).