Air pollution is an environmental issue around the world, especially the atmospheric fine particulate matters (PM2.5) posing critical impacts on human health through inhalation in the rapidly developing China. The PMs may be composed of numerous hazardous components, including toxic trace metals. However, most current air quality standards and abatement strategies are generally based on the total mass of PMs, thereby treating all particulates as equally toxic. Moreover, due to chemical speciation and matrix characteristics, only a fraction of the total pollutants in inhaled PMs is actually bioavailable. Therefore, total metal concentrations in bulk PMs might not accurately estimate the real health risks, and the human bioavailability of airborne metals becomes a key issue. In this study, both the physiologically based in vitro methods of SLF (Gamble’s solution) and DGT (originally used for ions in water and soil system) were tested or developed for evaluating the pulmonary bioaccessibility of trace metals in PM2.5, and the results of samples collected from three typical megacities of eastern and southern China during pollution seasons were compared, including Shanghai and Nanjing in Yangtze River Delta (YRD), and Guangzhou in the Pearl River Delta (PRD). The percentage of bioaccessible fraction (BAF%) of each metal relative to its total concentration in the PM sample is defined as bioaccessibility. According to the general results of the three cities, the SLF bioaccessibility of PM2.5 metals dissolved into lung fluid was in order of Ni&gt;Cr&gt;&gt;Cd&gt;Mn&gt;&gt;Pb, that Ni and Cr is relatively high (&gt;40%), while Pb is very low (average 3%). While for the DGT bioaccessibility of labile trace metals released in lung fluids which would be absorbed directly, all of them were very low (&lt;5%) and ranked as Ni&gt;&gt;Mn&gt;Cd&gt;&gt;Cr&gt;Pb. By further analysis of the proportions of DGT metals in SLF, Ni was slightly higher than Mn, Pb, and Cd, and Cr was the lowest, indicating that Ni was most inclined to be released and absorbed directly and quickly after the PM2.5 was inhaled into the lungs. For the spatial comparisons of various elements in different cities, both the SLF and DGT human bioaccessibility (%) of trace metals in PM2.5 of the PRD were higher than the YRD cities, especially the DGT results and Ni, Cr, and Cd. That may be mainly related to the differences in the sources of airborne metals and physicochemical properties of particulates from different regions.

Inhalation bioaccessibility of trace metals in PM2.5 from three megacities of China: Assessments by simulated lung fluid (SLF) and diffusive gradients in thin films (DGT)

255th National Meeting (2018)

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