Chemical structure and carcinogenicity relationships of some chloroalkene oxides and their parent olefins

Six epoxides of structurally related chloroalkenes were examined for their carcinogenicity by chronic testing in female ICR/Ha Swiss mice, 30/group. Repeated skin application three times weekly or s.c. injection once weekly were used for the life spans of the mice. The epoxides were: cis-1-chloropropene oxide, trans-1-chloropropene oxide, cis-1,3-dichloropropene oxide, trans-1,3-dichloropropene oxide, trichloroethylene oxide (TCEO), and tetrachloroethylene oxide (PCEO). In mouse skin, cis-1-chloropropene oxide, trans-1-chloropropene oxide, cis-1-,3-dichloropropene oxide, and trans-1,3-dichloropropene oxide induced statistically significant incidences of squamous carcinomas of the skin; TCEO did not cause any skin tumors; and PCEO resulted in three mice with benign skin tumors and one with a squamous carcinoma of the skin. Repeated s.c. injection of the four propene oxides induced statistically significant incidences of local tumors, mostly fibrosarcomas. This was not the case with TCEO and PCEO. The data are consistent with the carcinogenicity findings on the parent chloropropenes and suggest that the epoxides function as their activated carcinogenic intermediates. The essentially negative findings with TCEO and PCEO suggest further studies on the carcinogenicity of trichloroethylene and tetrachloroethylene.