3-nitrobenzanthrone, a powerful bacterial mutagen and suspected human carcinogen found in diesel exhaust and airborne particulates

9-Nitrobenzanthrone (3-nitro-7H-benz[d,e]anthracen-7-one) was isolated from the organic extracts of both diesel exhaust and airborne particles and was identified as a new class of powerful direct mutagen. its mutagenicity by Ames Salmonella assay is very high (208 000 revertants/nmol in Salmonella typhimurium TA98 and 6 290 000 revertants/nmol in YG1024) and compares with that of 1,8-dinitropyrene, which is the direct mutagen of strongest activity (257000 revertants/nmol in TA98 and 4 780 000 revertants/nmol in YG1024) so far reported in the literature. The new mutagen was also shown to induce micronuclei in mouse peripheral blood reticulocytes after intraperitoneal administration (micronucleated reticulocytes, 0.64% against 25 mg/kg dose after 48 h), suggesting its potential genotoxicity to mammalians. 3-Nitrobenzanthrone is most likely to be formed nor only during the combustion process of fossil fuels but also from the atmospheric reaction between benzanthrone and lower oxides of: nitrogen, since the latter ketone was found to be nitrated guile easily under an artificial atmosphere containing gaseous NO2(10 ppm) and O-3 (5 ppm)to produce the powerfully mutagenic 3-nitro derivative as the major product, along with several other isomeric mononitrobenzanthrones and dinitro descendants as minor products.