Urban air pollution and health risks of parent and nitrated polycyclic aromatic hydrocarbons in two megacities, southwest China

Ambient air pollution in China has a significant spatial variation due to the uneven development and different energy structures. This study characterized ambient pollution of parent and nitrated polycyclic aromatic hydrocarbons (PAHs) through a 1-year measurement in two megacities in southwest China where regional PM2.5 levels were considerably lower than other regions. Though the annual average BaP levels in both two cities were below the national standard of 1.0 ng/m3, however, by taking other PAHs into account, PAHs pollution were serious as indicated by high BaP equivalent concentrations (BaPEQ) of 3.8 ± 2.6 and 4.4 ± 1.9 ng/m3, respectively. Risk assessment would be underestimated by nearly an order of magnitude if only using BaP in risk assessment compared to the estimation based on 26 PAHs including 16 priority and 10 non-priority isomers targeted in this study. Estimated incremental lifetime cancer risks (ILCR) were comparable at two cities, at about 330–380 persons per one million, even though the mass concentrations were significantly different. Nitrated PAHs showed distinct temporal and site differences compared to the parent PAHs. High cancer risks due to inhalation exposure of PAHs and their polar derivatives in the low PM2.5-pollution southwest China suggest essential and effective controls on ambient PAHs pollution in the region, and controls should take potential health risks into account instead of solely mass concentration.