[Carcinogenicity of 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,4,7,8-hexachlorodibenzofuran when given by gavage to rats].

Previous studies showed that 2,3,4,7,8-pentachlorodibenzofuran (PenCDF) and 1,2,3,4,7,8-hexachlorodibenzofuran (HCDF) could produce tumors in the liver and subcutaneous tissues of rats by subcutaneous administration. The present study has examined the carcinogenicity of the same compounds in rats by oral administration. Wistar strain male rats were sacrificed at two years after oral administration (0.2 mg/rat) of 2,3,4,7,8-PenCDF or 1,2,3,4,7,8-HCDF. Among rats given 2,3,4,7,8-PenCDF, a cholangiohepatoma and a osteosarcoma were revealed in a rat each. Moreover, a few hepatic nodules were found in two rats in each experimental group. These results suggest that these compounds of polychlorinated dibenzofurans have a tumorigenic potency by oral administration.