Estimating the deposition of polycyclic aromatic hydrocarbons in human airways: The role of particle size

Most previous studies used atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) to estimate the risk of exposure via inhalation, but neglected the disparities in the effects of particle size. In this study, an extensive literature search retrieved data from 35 cities on atmospheric PAHs and particle size distributions, and a multiple-path particle dosimetry model was used to simulate the PAH deposition in human airways. The results revealed that the median concentration of total PAHs was 38 (range, 0.6–2074.2) ng/m3, while the median concentration of benzo(a)pyrene equivalent (B[a]Peq) was 11 ng/m3. Together with exposure to congener-specific PAHs, the median deposited concentrations of total PAHs or B[a]Peq were the highest in particulate matter (PM) with diameters of 1–2.5 μm, followed by > 1 μm and coarse PM, which can be explained by the general increase in proportions of high molecular weight PAHs with decreasing PM size. While the deposited PAHs were dominated by 3–5 rings PAHs, the deposited B[a]Peq was concentrated in 5-ring. Moreover, although differences in the contributions of the ring number between deposited and ambient PAHs were negligible, the contributions of fine PM were 11.9% and 9.5% greater for deposited PAHs and B[a]Peq, respectively. These results indicate that the risk of exposure to PAHs attached to fine PM is underestimated previously.