Pollution characteristics and health risks of size-resolved particulate-bound polycyclic aromatic compounds in Zhengzhou

Size-segregated particulate samples were collected from a megacity in Central China during four different seasons to determine the concentrations of polycyclic aromatic compounds (PACs), explore their size distributions, and evaluate their health risks. The annual average concentrations of Σ₁₇PAHs (polycyclic aromatic hydrocarbons), Σ₇NPAHs, and Σ₆OPAHs (nitrated and oxygenated PAHs) were 22.0 ng m⁻³, 0.59 ng m⁻³, and 4.65 ng m⁻³, respectively, which all exhibited significantly seasonal variations with peak values in winter. Five-to seven-ring PAHs were dominant, explaining 47.0%–63.5% of the Σ₁₇PAHs, with BbF being the most important component across the four different seasons. (2 + 3)-NFLT and 9,10-ATQ were the most abundant NPAHs and OPAHs, respectively. More than 60% of the PACs masses were enriched in fine particles (aerodynamic diameter (D_p) < 2.1 μm), and the mass median diameters (MMDs) of PACs were much less than 2.1 μm. The main sources of PACs identified by diagnostic ratios and principal component analysis (PCA) were coal/biomass combustion, vehicular exhaust emission, and secondary generation. Inhalation exposure assessment revealed that the annual average deposition efficiency of PACs was 48.2%, with PACs mainly deposited in the head airway (36.7%). The inhalation exposure pathway was more significant than the dermal absorption exposure pathway, whereas the incremental lifetime cancer risk (ILCR) for inhalation exposure (ILCR_inh) was slightly lower than the ILCR for dermal absorption exposure (ILCR_derm). The PACs in the fine particles (D_p < 2.1 μm) contributed more than half of the ILCR_inh values, but the coarse particles (D_p > 3.3 μm) contributed more than 76.2% of the ILCR_derm values. The total ILCR, including the ILCR_inh and ILCR_derm for adults, exceeded the acceptable limit of 10⁻⁶ set by the USEPA.