Mutagenicity and polycyclic aromatic hydrocarbons associated with extractable organic matter from airborne particles ≤ 10 μm in southwest Mexico City

A year-long sampling and analysis of 24h airborne particles equal to or less than 10 mu m (PM10) was conducted in Southwest (SW) Mexico City in 1998. The amount of airborne PM10 and its extractable organic matter (EOM) were highly correlated. The year 1998 was particularly dry with many fires, and higher values of PM10 and EOM were obtained in the fire period (February-May) compared to the without fire period (January, June-December). The indirect-acting mutagenicity (Salmonella typhimurium strain TA98 with mammalian metabolic activation, S9) did not correlate with the monthly concentrations of PM10 and EOM, while the direct-acting mutagenicity (strains TA98 and YG1021, without mammalian metabolic activation) did correlate. The highest monthly mutagenic potency of TA98 + S9 and of TA98-S9 were registered in May which correspond to the fire period, while for YG1021 the highest was in December, a without fire month. The highest TA98 + S9/TA98-S9 ratios appeared from April to September (with the exception of June), indicating that emission of the direct mutagens occurred in the rest of the year (the coldest months), and December showed the highest mutagenicity of YG1021. The correlation of this mutagenicity with the number of ground-based inversions indicated a greater emissions of nitroarenes in the coldest months emitted mainly by vehicular traffic as shown by the correlation between YG1021 with CO and with NO2. We did not find a correlation in the EOM of the complex mixtures between TA98 + S9 and the total concentration of polycyclic aromatic hydrocarbons (PAH) nor between TA98 + S9 and specific PAR The analysis by gas chromatography/mass spectrometry indicated the presence of retene, a PAH found in the fire period and considered a softwood burning marker. The concentrations of fluoranthene and benz[a]anthracene correlated with that of retene and with the burned area; they were the only PAH that presented significant differences between the periods with fire and without fire, showing that these compounds could have a similar origin. Benzo[ghi]perylene, coronene and indeno[1,2,3-cd]pyrene were the most abundant PAH of the 17 analyzed in SW Mexico City, indicating that the main emission source for PAH in the airborne particle phase in this zone were vehicles with the combustion of gasoline and diesel rather than wood burning. The mean concentrations for most PAH were higher during the fire period, except for perylene and coronene, suggesting that the fires were not the emission source for these two last PAR (c) 2006 Elsevier Ltd. All rights reserved.