Inhalation bioacessibility and absorption of polycyclic aromatic hydrocarbons (PAHs) in indoor PM2.5 and its implication in risk assessment

Highlights: • Inhalation bioaccessibility of PAHs ranged from 0.88 to 87.7%. • The bioaccessibility in the ALF was higher than that in GMB. • The absorption rate of PAHs was negatively related to number of rings. • The correction parameter was established to improve the risk assessment. Inhalation bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in PM_2.5 was assessed in numerous studies, however, the lung cell uptake and penetration of PAHs was seldom taken into account in risk assessment. In the present study, eighteen indoor PM_2.5 samples collected from Guangzhou, China were analyzed for the inhalation bioavailability of PAHs combining the inhalation bioaccessibility and cell absorption of PAHs. Two simulated epithelial lung fluid mimicking the healthy condition (as represented by gamble's solution (GMB), pH = 7.4) and the inflammatory condition (as represented by artificial lysosomal fluid (ALF), pH = 4.5) were employed to evaluate the inhalation bioaccessibility. The results indicated that the bioaccessibility of PAHs under the inflammatory condition (1.28%–87.7%) was higher than that under healthy condition (0.88%–87.6%). Naphthalene, phenanthrene, pyrene and benzo[a]pyrene were selected for absorption assay of lung epithelial cells (A549). The absorption rate of PAHs ranged from 64.7 to 90.7% and it was inversely proportional to the number of aromatic rings. Taken together, the inhalation bioavailability based on the bioaccessibility of PAHs and the lung cell absorption ratio ranged from 9.9 to 56.9% under the healthy state, from 12.7 to 65.6% under inflammatory condition. The correction parameter (F_c) was thus established and can be used to improve the risk assessment of human exposure to PAHs via PM_2.5 inhalation in future work.