Oncogenicity of K-region epoxides of benzo(A)pyrene and 7,12-dimethylbenz(A)anthracene.

Female Sprague-Dawley rats were given a subcutaneous injection of the parent hydrocarbon or its K-region epoxide in 0.1 ml sesame oil on alternate days to a total of 30 doses and observed for sarcoma at the site of injection for 275 days. The parent compounds, benzo(a)pyrene (0.2 mumole/dose) and 7,12-dimethylbenz(a)anthracene (0.2 mumole/dose), induced sarcoma in 100% of the animals with an average latent period of 101 and 95 days, respectively, whereas five of 12 rats (42%) injected with the K-region epoxide of B(a)P (1.0 mumole/dose), developed sarcoma in 151+/-22 days, and the K-region epoxide of DMBA (0.4 mumole/dose) failed to elicit tumors. Under these experimental conditions, these K-region epoxides are, at best, only weak carcinogens.