Analysis Of Fine Particulate Matter Components In Nanjing And Their Toxic Effects On Caenorhabditis Elegan

Although numerous studies have confirmed that atmospheric fine particulate matter(PM_2.5)has toxic effects on environmental organisms,most epidemiological studies only consider the mass concentration of PM_2.5 while ignoring the association of PM_2.5 components with various health endpoints.The key components and underlying mechanisms of health effects induced by PM_2.5 remain unclear.In this work,PM_2.5 samples were continuously collected in Nanjing from March 1,2021,to February 28,2022,and analyzed the seasonal distribution characteristics of each component in PM_2.5.The average concentration of PM_2.5 in the four seasons in Nanjing from high to low is winter>spring>autumn>summer.Water-soluble ions are the most abundant components in PM_2.5,accounting for more than 40%of the total mass of PM_2.5.In addition,organic carbon and elemental carbon also account for a high proportion of PM_2.5,accounting for 13.0-20.6%of the total mass of PM_2.5.In the four seasons,the content of heavy metals was low,accounting for 0.67-1.32%of PM_2.5 mass concentration.For PAHs,16 kinds of PAHs（naphthalene was not detected）only accounted for less than 0.1%of PM_2.5 mass concentration.The model organism Caenorhabditis elegans was selected to evaluate the toxicity of PM_2.5in different seasons.The results showed that PM_2.5 samples in four seasons had toxic effects on the development,locomotor behavior,and reproduction of C.elegans.At the physiological level,PM_2.5 exposure can inhibit growth and development,resulting in a decrease in the incidence of locomotion behavior.Meanwhile,PM_2.5 exposure also led to a significant decrease in brood size and the number of fertilized eggs in the uterus,resulting in impaired reproductive function of C.elegans.At the biochemical level,PM_2.5 can induce apoptosis and increase reactive oxygen species（ROS）production.At the molecular level,PM_2.5 can change the expression of stress-related genes.More importantly,the results highlight that oxidative stress and Deoxyribonucleic acid（DNA）damage may be a potential mode of action leading to adverse effects on insects.In addition,Pearson correlation analysis showed that insoluble components such as heavy metals and polycyclic aromatic hydrocarbons were significantly correlated with multiple toxicological endpoints,suggesting that heavy metals may be a key component of PM_2.5 toxic effects.In order to further verify the results of correlation analysis,the differences in induced toxicity of Total-PM_2.5,water insoluble components of PM_2.5(WIS-PM_2.5)and water soluble components of PM_2.5(WS-PM_2.5)were compared.Considering the persistence of PM_2.5 in the environment,the toxic effects of prolonged exposure on C.elegans were also studied.Studies have shown that acute exposure to these three components can adversely affect the development,movement behavior and reproduction of nematodes,and significantly induce germline apoptosis or ROS production.The toxic effects induced by prolonged exposure are more serious.Even prolonged exposure to low concentrations of PM_2.5 can cause adverse effects on nematodes.In addition,WIS-PM_2.5 showed stronger toxic effects than WS-PM_2.5,indicating that insoluble components contributed more to the toxicity of PM_2.5 and may be the main driving factor,which further verified the results of Pearson correlation analysis.It also reminds us that when evaluating the toxicity of PM_2.5,we should not only consider the size and dose of PM_2.5,but also fully consider the chemical composition of PM_2.5.Our study provides an important basis for revealing the underlying mechanism of toxic effects induced by PM_2.5 and assessing the potential risks of different components of PM_2.5 to environmental organisms.