Local application to mouse skin as a carcinogen specific test system for non-volatile nitroso compounds.

Using the epicutaneous test as an experimental model for detecting carcinogenicity, 3 doses each of nitrosomethylurea (NMU), nitrosonornicotine (NNN) and nitrosocarbaryl (NC) were administered to the skin of 65 female CFLP mice/group. To compare the carcinogenic potency of the nitroso compounds, benzo[a]pyrene (BaP) was taken as reference substance. Dose-response relationships were obtained for NMU and NC as well as for BaP. NNN exhibited only a weak carcinogenic effect in the dose range from 12.5 micrograms to 200 micrograms tested in the skin painting model. It showed, however, no dose dependent activity. After probit analysis of the results, the carcinogenic potencies of the nitroso compounds investigated in this system rank as follows: NC, 0.18; NMU, 0.04; NNN, 0.008 (BaP, 1.00).