Distribution, seasonal trends, and lung cancer risk of atmospheric polycyclic aromatic hydrocarbons in North China: A three-year case study in Dalian city.

Atmospheric monitoring data of polycyclic aromatic hydrocarbons (PAHs) over a three-year period were collected from an urban site in Dalian, northeast China. The status of PAHs in the atmosphere in Dalian were evaluated by assessing concentration levels, congener profiles, seasonal trends, primary source, inhalation exposure and the risk of developing lung cancer risk. Average concentrations were recorded for 53 PAHs (95 ± 40 ng/m3), 16 EPA priority PAHs (68 ± 33 ng/m3), 26 alkylated PAHs (17 ± 7.6 ng/m3) and 4 high-molecular-weight (302 Da) PAHs (1.3 ± 1.3 ng/m3). Atmospheric PAH concentrations in winter were almost twice as high as those recorded in the summer, possibly due to enhanced local emissions and long-range transport of atmospheric PAHs during the winter. PAH congeners were dominated by phenatherene, fluoranthene, pyrene and fluorene, accounting for 46.0% of total ∑53PAH concentrations. Ship/vehicle emission and mixed combustion were identified as the main sources of PAHs using diagnostic PAH concentration ratios and principal component analysis-multiple linear regression. Benzo(a)pyrene toxicity equivalent concentration had an average content of 32 ± 37 ng/m-3 over the sampling period, with dibenzo(a,h)anthracene (50.7%) and dibenzo(a,l)pyrene (26.4%) being the largest contributors. The risk of developing lung cancer due to inhalation exposure to outdoor PAHs was calculated at 12.0‰ using the overall population attributable fraction (PAF). Our results estimate that, due to PAH exposure in Dalian, the average excess lung cancer risk during a person's lifetime is 35.7 cancer cases per one million inhabitants.