Characterization of urban aerosol: seasonal variation of mutagenicity and genotoxicity of PM_2.5, PM₁ and semi-volatile organic compounds

Urban particulate matter (PM) is an environmental public health concern as it has been classified by the IARC as carcinogenic to humans (group 1) and it's well known that pollutants are more associated with the finest fractions of PM. In this study we characterize urban aerosol in Bologna, county town of Emilia-Romagna in the north of Italy, collecting PM_2.5, PM₁ and semi-volatile organic compounds using polyurethane foam. Samples were collected in three different seasons (winter, summer and autumn) and were extracted with acetone. On these three fractions we assessed mutagenicity using Salmonella reverse mutation test and genotoxicity by alkaline comet assay and micronucleus assay in human lung cancer cell line, A549. Organic extracts were also characterized for alkanes, polycyclic aromatic hydrocarbons (PAHs), nitrated and oxygenated PAHs. We also evaluated associations between the physicochemical parameters of samples and their genotoxicity. The particulate samples, collected in autumn and winter, indicated the presence of both base pair substitution and frameshift mutagens using TA98 and TA100 strains of Salmonella typhimurium and the mutagenicity was more associated with the finest fraction. Enhanced mutagenic response was observed in the absence of enzyme activation. Only a third of comet and a half of micronucleus assays gave positive results that, unlike Salmonella's ones, are not season-related. These results were compared with environmental chemicals concentrations and we found that Salmonella's data correlated with PAHs detected on PM filters and with mass concentrations, whereas the DNA damage correlate only with PAHs extracted from polyurethane foams. The use of different assays was sensitive to detect and identify different classes of airborne mutagenic/genotoxic compounds present in aerosol, showing that monitoring air quality using this methodology is relevant.