Identification of mammalian cell genotoxins in respirable diesel exhaust particles by bioassay-directed chemical analysis

A bioassay-directed chemical analysis which consists of mammalian cell bioassays (comet assay, CBMN assay and EROD-microbioassay) in conjunction with analytical measurements was performed to identify the most biologically active compounds of the diesel exhaust particulate matters (DEPs) on mutagenic activity. These bioassay systems were suitable to estimate the mammalian genotoxic potentials of pollutants present in low concentrations in limited environmental samples, as is the case with DEPEs. The results from mutagenic assay showed that the aromatic and slightly polar fraction of DEPs induced chromosomal damage and DNA breakage in a non-cytotoxic dose. It was also revealed that indirect-acting mutagens may mainly contribute to the mutagenic effect of aromatic fraction via the enzyme metabolism system. In the aromatic fraction, several indirect-acting mutagenic PAHs such as dibenzo(a,h)anthracene, chrysene, and 1,2-benzanthracene were detected by GC-MS and the complex mixture effect of this fraction was quantified in terms of its biological-TCDD equivalent concentration (bio-TEQ) which was 32.82 bio-TEQ ng/g-DEPs by EROD-microbioassay. Conclusively, we confirmed that indirect-acting mutagens contained in aromatic fraction may be important causatives of the genotoxicity of extracts of DEPs by integrating the results obtained from a mammalian cell bioassay-directed fractionation.