The role of nitroaromatic compounds in the direct-acting mutagenicity of diesel particle extracts

The Salmonella mutation assay has been adapted to a number of experimental procedures used to characterize the chemical components and molecular mechanisms involved in the direct‐acting mutagenicity of diesel particle extracts. The mutagens were found to be unreactive towards purified DNA. Mutagenic activity was decreased in nitroreductase‐deficient bacteria and increased in the absence of oxygen, suggesting that bacterial enzymes activate the mutagens. The extract was fractionated by thin layer chromatography using both normal and reverse phase silica gel plates. On normal silica plates, a separation was made between unsubstituted PAH, nitro‐PAH and the more polar aromatic compounds. About a third of the mutagenic activity in the particle extract was recovered in fractions containing monosubstituted nitro‐PAH compounds. The absorption spectra and reverse phase chromatographic properties indicate 1‐nitropyrene is a predominant component but not the only mutagen in these fractions. The remaining activity was in the more polar fractions, and mutagenicity assays using anaerobic conditions and nitroreductase‐deficient bacteria suggest they contain other nitro‐substituted compounds.