Coal and biomass combustion emissions increase the cancer and health risks of polycyclic aromatic hydrocarbons in PM2.5 from Nanchang, central China

This study collected 365 daily PM2.5 samples from Nanchang City and analysed the characteristics, sources, and risks of polycyclic aromatic hydrocarbons (PAHs). The findings indicated that the yearly average ΣPAH concentration (the sum of 15 PAHs) was 7.20 ± 4.52 ng m−3, with the highest concentration in winter (12.24 ± 4.95 ng m−3), followed by autumn (7.05 ± 3.1 ng m−3), spring (5.85 ± 2.47 ng m−3) and summer (3.76 ± 1.72 ng m−3). The molecular characteristics and diagnostic ratios analysis suggested that the PAHs originated from vehicle exhaust, combustion (coal and biomass), and petroleum volatilisation. The results of quantitative estimation showed that vehicle exhaust and combustion sources contributed the most (about 43% and 40%) to PAHs. The petroleum industry accounted for a smaller proportion, approximately 17%. Seasonally, combustion sources (coal and biomass) contributed more in winter (56%) and autumn (51%), whereas vehicle exhaust contributed more in summer (51%) and spring (54%). High atmospheric pressure inhibited the diffusion of PAHs but high temperatures may have promoted PAH decomposition. The results of the risk assessment showed that Nanchang residents exposed to PAHs face a potentially low carcinogenic risk but a definite non-carcinogenic health risk during autumn and winter. Furthermore, adults had greater cancer and health risks compared to children. During autumn and winter, it is probable that combustion emissions were the primary contributing factor to risks of PAHs.