Size Distributions and Health Risks of Atmospheric Particulate Polycyclic Aromatic Hydrocarbons in an Inland Urban Area of Baoding, China.

Abstract

Previous health risk assessments of particulate polycyclic aromatic hydrocarbons (PAHs) have ignored the size distributions and respiratory tract deposition rates, resulting in significant bias. To calculate the health risks of depositing PAHs, this study investigates the size-resolved dynamics of particulate PAHs and associated deposition fluxes in Baoding, a representative inland city in China's Beijing-Tianjin-Hebei air pollution corridor. Size-segregated aerosol sampling (n = 20 batches) across four seasons revealed: coarse particles (> 2.1 μm) dominated PM mass in spring (67%), summer (60%), and autumn (60%), while winter exhibited fine particle (< 2.1 μm) dominance (62% of TSP). All PAHs demonstrated bimodal size distributions with accumulation (0.43-0.65 μm) and coarse modes (4.7-5.8 μm). Low-molecular-weight PAHs show more significant volatility-driven migration to coarse particles than high-molecular-weight PAHs. The deposition fluxes of size-segregated PM and PAHs were calculated by multi-path particle dosimetry model. Compared with adults, children have a 32-40% higher flux of coarse PM deposition. In addition, the deposition fluxes of coarse PM is higher than fine PM. These findings challenge conventional fine PM-centric risk frameworks, highlighting the necessity to reconsider coarse PM toxicity for child-specific exposure in northern China's inland cities.