Absence of carcinogenicity of 1-nitropyrene, correction of previous results, and new demonstration of carcinogenicity of 1,6-dinitropyrene in rats.

1-Nitropyrene (1-NP), 1,6-dinitropyrene (1,6-DNP) and 1,8-dinitropyrene (1,8-DNP), which are potent mutagenic components of diesel exhaust and air pollutants, were injected subcutaneously into the back of F344 rats. No tumor was induced by experimental day 650 in rats treated with 40 or 4 mg of 1-NP. On the other hand, 1,6-DNP at a total dose of 4 mg was demonstrated to induce sarcomas at the injection site in all 10 rats. 1,8-DNP at total doses of 0.4 and 0.04 mg also induced sarcomas in 10 and 9 out of 10 rats, respectively, by day 320. Our previous finding that 1-NP was carcinogenic was possibly due to contamination of the preparation with dinitropyrenes.