DNA adducts and oxidative DNA damage induced by organic extracts from PM2.5 in an acellular assay

The genotoxic activities of complex mixtures of organic extracts from the urban air particles collected in various localities of the Czech Republic, which differed in the extent and sources of air pollution, were compared. For this purpose, PM2.5 particles were collected by high volume samplers in the most polluted area of the Czech Republic--Ostrava region (localities Bartovice, Poruba and Karvina) and in the locality exhibiting a low level of air pollution--Trebon--a small town in the non-industrial region of Southern Bohemia. To prepare extractable organic matter (EOM), PM2.5 particles were extracted by dichloromethane and c-PAHs contents in the EOMs were determined. As markers of genotoxic potential, DNA adduct levels and oxidative DNA damage (8-oxo-7,8-dihydro-2'-deoxyguanosine, 8-oxodG, levels) induced by EOMs in an acellular assay of calf thymus DNA coupled with ³²P-postlabeling (DNA adducts) and ELISA (8-oxodG) in the presence and absence of microsomal S9 fraction were employed. Twofold higher DNA adduct levels (17.20 adducts/10⁸ nucleotides/m³ vs. 8.49 adducts/10⁸ nucleotides/m³) were induced by EOM from Ostrava-Bartovice (immediate proximity of heavy industry) compared with that from Ostrava-Poruba (mostly traffic emissions). Oxidative DNA damage induced by EOM from Ostrava-Bartovice was more than fourfold higher than damage induced by EOM from Trebon (8-oxodG/10⁸ dG/m³: 0.131 vs. 0.030 for Ostrava-Bartovice vs. Trebon, respectively). Since PM2.5 particles collected in various localities differ with respect to their c-PAHs content, and c-PAHs significantly contribute to genotoxicity (DNA adduct levels), we suggest that monitoring of PM2.5 levels is not a sufficient basis to assess genotoxicity of respirable aerosols. It seems likely that the industrial emissions prevailing in Ostrava-Bartovice represent a substantially higher genotoxic risk than mostly traffic-related emissions in Ostrava-Poruba. B[a]P and c-PAH contents in EOMs are the most important factors relating to their genotoxic potential.