Bioaccessibility, source impact and probabilistic health risk of the toxic metals in PM2.5 based on lung fluids test and Monte Carlo simulations

Abstract

The soluble toxic metals (TMs) in PM2.5 have attracted increasing attention due to their high bioaccessibility and toxic potential. Here, the bioaccessibility of the TMs was determined by simulated lung fluids (SLFs), including acidic artificial lysosomal fluid (ALF) and neutral Gamble’s solution (GS). An extraction time of 48 h was determined by dissolution kinetics. The bioaccessibility for most TMs in ALF was significantly higher than that in GS, especially for Cd and Pb. Five TM sources were identified by positive matrix factorization (PMF), and their correlation with the bioaccessibility of the PM2.5-bound TMs was examined. This showed a significant negative correlation (p < 0.01) of the mass contribution of resuspended dust and a positive correlation (p < 0.01) of that of coal combustion with the bioaccessibility of some TMs, which implicated a limit vs. high potential risk of these two sources. By introducing the variability of the bioaccessibility, the probabilistic noncancer (HQ) and cancer risks (ILCR) of the soluble TMs were estimated by Monte Carlo simulations under both ALF and GS scenarios. This showed that the noncancer risk of As and the cancer risk of most TMs cannot be neglected due to their relatively high probability of exceeding the safety threshold (HQ > 1 and ILCR>1 × 10−6).