Comparative tumor initiating activity on mouse skin of 6-nitrobenzo[a]pyrene, 6-nitrochrysene, 3-nitroperylene, 1-nitropyrene and their parent hydrocarbons

6-Nitrobenzo[a]pyrene, 6-nitrochrysene, 3-nitroperylene, 1-nitropyrene, and the corresponding parent hydrocarbons were tested for tumor initiating activity on mouse skin with promotion by tetradecanoylphorbol acetate. The initiating doses of 6-nitrobenzo[a]pyrene and benzo[a]pyrene were 0.05 mg each; for all other compounds the initiating doses were 1.0 mg. 6-Nitrochrysene induced tumors in 60% of the mice (2.1 tumors per mouse), but was significantly less tumorigenic than chrysene. 3-Nitroperylene induced tumors in 42% of the mice (0.5 tumors per mouse) and was significantly more active than perylene. Neither 1-nitropyrene nor 6-nitrobenzo[a]pyrene exhibited significant tumorigenic activity in the concentrations tested.