Cytotoxicity Studies On Main Components Of Toluene Secondary Organic Aerosol

A large number of epidemiological and toxicological studies have shown that the increase of the morbidity and mortality of the heart and lung diseases are significantly related to the increase of the concentrations of fine particulate matter(PM_2.5),which means the atmospheric PM_2.5 pollution has become one of the major environmental factors that affect human health.The secondary organic aerosols（SOA）formed by atmospheric oxidation of volatile organic compounds（VOCs）are the main components of PM_2.5.However,there are few studies on the biological toxicity of the components in SOA and the interaction between them.In this study,toluene was used as the SOA precursor and three main components of toluene SOA（benzoic acid,benzaldehyde and pyruvic acid）were selected as the research subjects.The cytotoxic effects of the three main components were investigated by exposure to the human lung epithelial cells（A549）.In this study,the effects of the single component of benzoic acid,benzaldehyde and pyruvic acid on the activities of extracellular LDH,ROS,SOD,GSH,inflammatory factors（IL-6,IL-8,TNF-α）in A549 cells were investigated.The results showed that with the increase in the exposure concentrations of the three components,the level of ROS in A549 cells increased and showed a significant dose effect relationship.The three components had no significant effect on the permeability of A549 cell membrane,and no significant changes among GSH,SOD,IL-6,IL-8 and TNF-α.The toxicity of the twocomponent mixtures was found to be significant and the ROS level in A549 cells increased unexpectedly.The mixture of benzoic acid and pyruvic acid had the strongest ability to stimulate A549 cells to produce ROS.The twocomponent exposures caused the abnormal drop of TNF-α in A549 cells,and showed a certain dose-effect relationship.The joint toxicity of two-component among benzoic acid,benzaldehyde and pyruvic acid was investigated by 2×2 factorial experimental design.The results showed benzoic acid,benzaldehyde and pyruvic acid had combined toxic effects and could aggravate cytotoxicity.The two-component mixtures were found to have,the interactive,antagonistic or synergistic functions for the generation of LDH,ROS,SOD,GSH,and inflammatory factors（IL-6,IL-8,TNF-α）in A549 cells.According to the compositions of benzaldehyde,benzoic acid and pyruvicacid in SOA samples produced from the chamber experiments under different environmental conditions,the three-component mixture solutions were prepared.The effects of environmental conditions on the cytotoxicity of the three components in SOA generated from toluene,as well as the effects of introducing benzoic acid to the system of benzaldehyde and pyruvic acid on the cytotoxicity were investigated.The results showed that the change of the precursor concentrations had a significant effect on LDH,ROS,IL-8 and TNF-α in A549 cells.With the increase of the precursor concentrations,the membrane permeability decreased and the secretion of ROS,IL-8 and TNF-α increased.The three-component mixtures of benzoic acid,benzaldehyde and pyruvic acid in SOA in the presence of the neutral seed aerosols tended to stimulate the generation of ROS、 IL-8 and TNF-α,causing or aggravating oxidative damage and inflammatory reaction.The three-component mixtures changed the permeability of cell membrane in the absence of seed aerosols.A certain concentrations of benzoic acid could promote the formation of extracellular LDH and intracellular SOD when the cells were exposed to benzaldehyde and pyruvic acid,but inhibited the mixture of benzoate aldehyde and pyruvate to stimulate A549 producing ROS.In addition,the stimulative effect of benzoic acid on TNF-α production was greater than the inhibition effect of the twocomponent mixture of benzaldehyde and pyruvate.