Carcinogenicity Examination of 1-Nitropyrene Oxides and Related Chemicals: Lack of Their Tumorigenic Effects in a Newborn Mice Assay.

Carcinogenicity of 1-nitropyrene (NP) oxides (1-NP 4, 5-oxide and 1-NP 9, 10-oxide) and related chemicals (1-NP and 1-nitro-6-hydroxypyrene) was examined in the newborn mouse model by i.p. administration at 1, 8, 15 days after birth (each chemical was given at a total dose of 700 nmol per mouse). Low incidences of hepatocellular neoplasms were recognized in male mice exposed to either of these chemicals. However, the incidences were not significantly different from those of animals given solvent alone or of non-treatment. Lymphoma was infrequently seen in female mice given some of tested chemicals. The incidences were also not significantly different from those of mice with the solvent alone or of the controls. The results suggest that although these aromatic hydrocarbons exert genotoxicity or mutagenicity, they may not be potent carcinogens, or the assay with use of newborn mice may be insufficient to monitor carcinogenicity of such chemicals.