Chemical and Biological Characterization of Southern Ontario Urban Air Particulate
Ambient concentrations of polycyclic aromatic compounds [PAC], other air pollutants and the mutagenic potency of respirable air particulate extracts were used to study air quality in Hamilton from May of 1990 to June of 1991. Concentrations of polycyclic aromatic hydrocarbons [PAH], thiaPAH, oxygenated PAC and in some cases nitroPAH as well as the mutagenic activity caused by these compounds were determined in 68 samples of air particulate, collected over a number of days with widely varying air pollutant concentrations and atmospheric conditions. Chemical analyses of the non-polar aromatic fractions of the air particulate extracts showed a 550-fold range in PAC concentrations, from 0.31 to 170 ng/cubic metre air, while biological assays showed a 140-fold range of mutagenic potencies. The non-polar aromatic fraction represented about three-quarters of the sum of the mutagenic responses in the polar and non-polar aromatic fractions. The mutagenicity and PAC concentrations of air particulate collected in Hamilton are low to average compared to air particulate samples collected in other cities around the world. Relationships between mutagenic potencies, PAC concentrations and atmospheric condistions were examined using principal component analysis, which revealed good positive correlation between the mutagenic potencies of the non-polar aromatic fractions, nitrogen diozide and sulfur dioxide concentrations. Average windspeed and ozone concentrations were inversely correlated with mutagenicity. Principal component analysis also show that sprigtime thermal inversion episodes correlated with conditions favoring the atmospheric transformation of PAH to mutagenic nitroPAH. The mutagenic potency of the non-polar aromatic fraction of air particulate extract rose in direct proportion to nitroPAH concentrations arising from atmospheric transformation. Enhanced-sensitivity strains of Salmonella typhimurium were used in all bioassays of air particulate extract mutagenicity, thereby making more extract available for extensive chemical analyses. For example, bioassay analyses of a pooled sample of air particulate extract were carried out using six different strains of S. typhimurium. Strains containing increased levels of enzymes responsible for metabolizing compounds such as nitroPAH showed 7- to 10-fold enhance mutagenic responses compared to standard tester strains. Normal-phse HPLC seperation of the non-polar aromatic fraction of the pooled air particulate extract was combined with bioassays utilizing three different enhanced-sensitivity S. typhimurium strains, allowing quantitation of individual mutagens through analytical chemical methods as well as accurate determination of the mutagenic activity arising from each compound. Normal-phase HPLC separation was also used in the bioassay-directed fractionation of an extremely mutagenic air particulate sample collected at the side of Highway 404 in Toronto, Ontario. NitroPAH arising from combustion sources were determined to be responsible for virtually all of the mutagenic activity detected in this particular sample, from which was isolated a potent mutagen not previously described in air particulate extracts -3.8-dinitrofluoranthene.