INVOLVEMENT OF NITRO-COMPOUNDS IN THE MUTAGENICITY OF URBAN PM2.5 AND PM10 IN TURIN

Fine particles can be active carriers of toxic compounds into the alveoli of lungs. Among these compounds are numerous mutagens and carcinogens. The direct acting mutagenicity per unit mass of fine particulate matter (PM) is significantly higher than those of coarse particles, especially in urban areas. In this study, the mutagenic properties of urban PM2.5 and PM10 were evaluated, and the role of nitro-compounds was estimated. PM2.5 and PM10 samplings, NOx and some PAHs determinations were performed daily in 2007 in Turin following a consolidated in vitro test – the Salmonella assay – that was conducted with PM2.5 and PM10 organic extracts. The mutagenic properties were assessed for each month of sampling with S. typhimurium TA98- and TA98-derived strains: a nitroreductase-less mutant strain (TA98NR) and an added nitroreductase-producing plasmid strain (YG1021). The annual measured mean levels of PM2.5 and PM10 were 34±20 and 48±18 µg/m3. The PM2.5/PM10 ratio ranged from 0.36 to 0.89. The Salmonella assay showed higher mutagenicity in autumn/winter (20±15 TA98NR, 54±39 TA98, 173±161 YG1021 net revertens/m3) with respect to spring/summer (2±2 TA98NR, 7±8 TA98, 24±27 YG1021 net revertens/m3)(p<0.01). There are also statistically significant seasonal differences in the gravimetric analysis data. The ratio between the TA98 net revertants per PM2.5 µg is 6.5 times greater than per PM10 µg. Moreover, the bioassay results showed an amplified response in the YG1021 strain and a reduced response in the TA98NR strain. The net revertant ratio TA98NR/YG1021 is equal to 11±4 for PM2.5 and 13±6 for PM10 organic extracts (p<0.01). There is a significant correlation with NOx and PAHs concentrations. These findings can describe the relevant role of nitro compounds, and they underline the priority in prevention improvements to reduce nitrated molecule air pollution.