Characteristics Of Atmospheric PM_2.5in Nanjing And Cytotoxicity In Human Lung Epithelial Cells A549

In recent years,air pollution has become one of the most pressing public health issues in China which occurred frequently,covered a wide range,and last for a long time.As the main pollutant,PM2.5 can adsorb a variety of toxic and harmful substances,enter the human body,and seriously threate human health because of the small particle size,large specific surface area.A large number of studies have shown that the concentration of PM2.5 is positively correlated with the admission rate and mortality of respiratory diseases,but its specific toxic components and toxic mechanisms are not yet clear.PM2.5 is a mixture of multiple chemicals,whose composition is greatly influenced by the type of sources,locations and atmospheric conditions.Furthermore,the health effect of PM2.5 varies according to its chemical composition.In order to investigate the toxic effects of atmospheric PM2.5 from different sources,PM2.5 samples were collected from three sites(a traffic site,an industrial site and a residential site located on campus)in Nanjing.The sampling was conducted from January till March 2016.The contents of particulate-bound water-soluble ions,metal elements and OC,EC were analyzed by ion chromatography,inductively coupled plasma mass spectrometry and carbon analyzer respectively.Cytotoxicity and PM2.5-induced oxidative stress in human lung epithelial cells(A549 cells)were also determined.The results showed that the daily PM2.5 mass concentrations in both traffic and industrial sites were much higher than the National Standard of the People's Republic of China Ambient Air Quality Standard(NAAQS)Grade ? 24-h standard(GB3095-2012,75 ?g/m3).The major water-soluble ions(SO42-,NO3-and NH4+)accounted for 80.6%to 85.0%of the total water-soluble ions,which was mainly affected by secondary pollution in Nanjing.At present,the fixed source is still the main source of pollution,but motor vehicle pollution is intensifying and it may become the main source of air pollution in the next few years with the contribution of coal combustion to atmospheric pollution declining.The analysis of enrichment factors for metal elements showed that vehicle exhaust gas and coal-fired fuel might contribute more to the atmospheric PM2.5.The carbon component is also an important part of PM2.5 in Nanjing,and the correlation between OC and EC is not significant resulting from the formation of SOC.The main sources of OC and EC during sampling period may be coal combustion and biomass combustion,and there is secondary conversion of pollutants.Particles from all sites inhibited the cell activity over our dosage range(50,100,200 and 400?g/mL),and presented a linear dose-response relationship.The cell viability of A549 was the most sensitive to PM2.5 samples from the industrial site,with an IC50 value of 229.1 ?g/mL.In contrast,the industrial PM2.5 samples induced the lowest contents of ROS,which may be caused by the relatively low Zn contents or the dynamic changes in ROS expression under acute-high concentration exposure.The amount of ROS production increased with the increase of exposure concentration,and the trend of particles in traffic and living areas was consistent under the concentration gradient.However,each sampling point reaches the peak of ROS production in a certain period of time,and then both decrease and tend to be flat under the time gradient.It may be related to the self-regulation of cell or unknown components in PM2.5.In future,the contributions of each component to particulate toxicity should be further studied.