Mutagenic activity of urban air samples and its modulation by chili extracts.

Different samples of ambient particulate organic matter were collected during the summer and winter of 1990 in Mexico City. After dichloromethane extraction, the samples were tested for mutagenicity with derivatives of Salmonella typhimurium possessing high activity of 'classical' nitroreductase (YG1021) or O-acetyltransferase (YG1024), and compared to the mutagenicity of the normal strain YG1020, and to that of a nitroreductase-deficient mutant TA98NR. The two enzyme-overproducing strains were more sensitive to the mutagenic effect of the extracts than the parent and deficient strains. The sensitivity order, i.e., YG1024 > YG1021 > YG1020 > TA98NR, emphasizes the usefulness of the new Salmonella strains in analyzing the mutagenicity of complex mixtures and suggests that some of the direct mutagenic compounds in the urban air samples are nitro-aromatics. Investigations were also conducted to analyze the effect of chili extract on the mutagenicity of an urban air sample. The extract itself showed moderate mutagenic activity and an additive effect was noted when both the chili and air extracts were present. On the other hand, the maximum volume of chili tested produced a decrease in the number of revertants without affecting the background lawn of bacterial growth. The same response was also observed when 1-nitropyrene, 1,6-dinitropyrene or 1,8-dinitropyrene was used as the genotoxic compound, although potentiation instead of addition occurred at low vegetable volumes. At the concentrations found in the chili extract, chlorophyllin and beta-carotene showed an antimutagenic effect against the nitro-aromatic compounds.