Dominant Combustion Sources of PM_2.5-bound PAHs and Associated Cancer Risk in Wuhan, Central China

Polycyclic aromatic hydrocarbons (PAHs) are pollutants of substantial concern due to their carcinogenic and mutagenic properties. This study involved 24-h PM_2.5 sampling conducted from October 14, 2021, to January 8, 2022, at a suburban site in Wuhan, central China. An in-injection port thermal desorption-gas chromatography/mass spectrometry procedure was used to determine 14 PAHs in the particulate phase. The average concentrations of total PAHs and benzo(a)pyrene carcinogenic equivalent concentration are 15.2 ± 8.2 ng m⁻³ and 0.87 ± 0.73 ng m⁻³, respectively, with a predominant presence of 4-ring PAHs (59.6%), particularly chrysene. Four sources of PM_2.5-bound PAHs are identified using a positive matrix factorization model along with diagnostic ratios. These sources, in descending order of contribution, are coal combustion and ship emissions (42.8%), diesel- and gasoline-powered vehicles (27.1%), biomass burning (23.5%), and iron and steel industry/cement plants (6.6%). The lifetime excess cancer risk due to inhaling PM_2.5-bound PAHs are 1.69 × 10^–6 and 1.34 × 10^–4, with emissions of diesel- and gasoline-powered vehicles accounting for 60.2% of the risk. This indicates a high likelihood of cancer risk in suburban Wuhan associated with these exposures, and underscores the urgency of regulating the sources rather than merely the concentration of pollutants.