A carcinogenicity study of diphenylarsinic acid in C57BL/6J mice in drinking water for 78 weeks.

Diphenylarsinic acid (DPAA), a neurotoxic organic arsenical, is present in groundwater and soil in some regions of Japan owing to illegal dumping. The present study evaluated the potential carcinogenicity of DPAA, including investigating whether bile duct hyperplasia in the liver that was observed in a chronic study on 52 week mouse, develops into a tumor when administered to mice in their drinking water for 78 weeks. DPAA was administered to 4 groups of male and female C57BL/6J mice at concentrations of 0, 6.25, 12.5, and 25 ppm in drinking water for 78 weeks. A significant decrease in the survival rate was found for females in the 25 ppm DPAA group. Body weights of males in the 25 ppm and females in the 12.5 and 25 ppm DPAA groups were significantly lower than those of the controls. Histopathological evaluation of neoplasms in all tissues showed no significant increase in tumor incidence in any organ or tissue of 6.25, 12.5, or 25 ppm DPAA-treated male or female mice. In conclusion, the present study demonstrated that DPAA is not carcinogenic to male or female C57BL/6J mice. Taken together with the fact that the toxic effect of DPAA is predominantly restricted to the central nervous system in humans, and the finding that DPAA was not carcinogenic in a previous 104-week rat carcinogenicity study, our results suggest that DPAA is unlikely to be carcinogenic in humans.