Cr(VI)/Pb2+ are responsible for PM2.5-induced cytotoxicity in A549 cells while pulmonary surfactant alleviates such toxicity

The composition of PM2.5 is extremely complicated, making the causes of PM2.5-induced toxicity hard to understand. To identify the major toxic components of PM2.5 particles, we used reductionism approach, synthesized and investigated a model PM2.5 library containing 24 carbon nanoparticles with adsorbed pollutants including Cr (VI), Pb2+, As(III) and BaP either individually or in combinations. Our data showed that major physicochemical characteristics of model PM2.5 library members were similar to PM2.5 particles from Guangzhou city (PM2.5-GZ). Cytotoxicity of lung cells (A549) was increasing as the member of adsorbed pollutants at environment relevant concentrations. Using these model particles, we identified that co-existence of Cr(VI) and Pb2+ components contributed to the PM2.5-induced cytotoxicity in A549 cells. Besides, pulmonary surfactant reduced the PM2.5-induced cytotoxicity in A549 cells probably via enhancing cell autophagy. The findings from this study suggest that systematic investigation using model PM2.5 particle library helps identify key toxic pollutants in otherwise very complex PM2.5 particles and facilitate our understanding of the underlying biological mechanisms.