Research On The Toxicological Assessment Of Different Organic Fractions In Atmospheric Particulate Matters In Beijing

PM10 and PM2.5 have adverse effects on human health. Although the results of toxicological research in vitro have shown that PM induces several types of adverse effects, the biological mechanisms behind these associations are not fully understood. The goal of this study is to investigate the mutagenicity, DNA damage and repair, cytotoxicity, apoptosis and the effect on cell cycle of PAHs and Non-hydrocarbons (NHs) extracted from the atmospheric particulates (PM10 and PM2.5) collected from different sites, seasons(summer and winter)respectively and to detect the effect of these factors on the toxicological activity of PAHs and NHs. And then determine which one is mainly responsible for the toxicity of PM. The assays used are Salmonella mutagenicity assay, using Salmonella typhimurium strains TA98 and TA100 with and without metabolic activation (S9), Comet assay, MTT assay (RAW264.7 and A549 cell lines) and flow cytometry. The characteristics of PM10 and PM2.5 from 9 sampling sites in winter is investigated either in this study. The dissertation made the following results:1) The pollution level in Beijing is very serious. The mass concentrations of PM during daytime are higher than nighttime. In all sampling sites, the percentage of organic subfractions from big to small is asphaltene, non-hydrocarbons, aliphatic hydrocarbons and polycyclic hydrocarbons. 2) All samples are mutagenitic. The mechanism of mutagenicity of PAHs was a frame-shift mutation and PAHs from Coking plant mostly were indirect-acting mutagens. All samples have potency to make cell viability decrease (perhaps induced by oxidative stress), to retard cells at G0/G1phase and G2/M phase, to induce apoptosis and DNA single strand breakages, double strand breakages and DNA-protein crosslinks. And compared with PAHs, NHs are responsible for the toxicity from PM. 3) The sampling sites, seasons and particle size are important factors to the toxicological potency of PAHs and NHs. In general, the smaller PM size have the higher toxicity; and the toxicity of the samples in winter is higher than that in summer; and the toxicity of the samples from coking plant is the highest in 3 sampling sites. 4) DNA single strand breakages are more prone to be repaired than double strands breaks and DNA-protein crosslinks. 5) DNA damages are one of the main mechanisms of the mutagenicity induced by PAHs and NHs from 3 different sampling sites. DNA damages result in cell cycles retarding at G0/G1 phase and G2/M phase to repair. The cells in which DNA cannot be repaired, will be induced apoptosis or mutation, as a result, the cell viability decreases. Oxidative damage might be one of the main mechanisms of DNA damages.