A Comparative Study Of Atmospheric Particulate Matter And Nanoparticles And Their Toxic Effects On Heavy Metals

Atmospheric particulate matter(PM)is one of the main culprits of air pollution,which poses a serious threat to human health.Due to the wide range of sources,variable components and complex properties of PM,people currently know little about the toxic effects of each component in PM and the interaction between the components.Among them,although the heavy metal components only account for a small part of the mass concentration of PM,with characteristics of non-biodegradability,easy bioaccumulation,and high biological toxicity,and interactions within and with the rest of the PM,heavy metal as a toxic component cannot be ignored in PM.In order to comprehensively study the toxic effects of heavy metals in PM,this paper first took nanoparticles(NPs)as the entry point to compare and analyze the toxic effects of PM and NPs on human lung epithelial cells A549,and selected NPs with controllable structure and simple composition as the simplified“core”model for the study of PM.On this basis,the combined toxicity of PM and heavy metals and their interaction mechanism were simulated,and the toxic effects of PM on heavy metals were explored,with a view to providing theoretical support in terms of assessing the health risk and managing environment safety of PM components.The main research contents and results are as follows:(1)Comparative study on toxicity of atmospheric particulate matter and nanoparticlesAccording to the main components of PM,four kinds of carbonaceous NPs,three kinds of metal NPs and silica NPs were selected as the potential simplified model of PM.The results of cell viability experiments showed that the median effect concentration EC₅₀ of the standard sample of atmospheric particulate(148.7?g/mL)was the closest to the silica NPs(177.9?g/mL),which was between carbonaceous NPs and metal NPs.Both PM standard samples and NPs induced different degrees of intracellular reactive oxygen species(ROS)increase and adenosine triphosphate(ATP)reduction:when the concentration was 50?g/mL,there was no significant difference in ROS induction and ATP inhibition between carbon NPs and PM(p>0.05),while the silica NPs significantly inhibited the synthesis of ATP(3.9±0.1%vs.control).Comprehensive analysis showed that carbonaceous NPs have the potential to be used as the simplified“core”model of PM.(2)Combined toxicity analysis of atmospheric particulate matter and nanoparticles with heavy metalsThe PM standard sample treated with Chelex 100 chelating resin(Chelex-PM)and four previously identified carbonaceous NPs were selected for joint toxicity study with eight typical heavy metals from PM.The results showed that the effect of particulate matter on metals toxicity was related to the concentration:at low metal concentrations,the cytotoxicity(cell viability was 58.7-74.6%)caused by the co-exposure of Chelex-PM and metal was higher than that of metal alone(cell viability was 81.3-92.5%);as the metal concentration increased,the presence of particulate matter may reduce the toxic effects caused by the metal;as the concentration of particulate matter and metals increased,the interaction modes between particulate matter and metals had mostly changed from additive to antagonistic.The presence of particulate matter has a great impact on heavy metal toxicity;PM and carbonaceous NPs have similar interaction modes with metals.(3)Preliminary study of interaction mechanism between atmospheric particulate matter and nanoparticles with heavy metalsOxidative stress is an important mechanism of cytotoxic effects caused by particulate matter and heavy metals.In order to explore the mechanism of interaction between particulate matter and metal to control the health hazards of particulate matter,we selected the previously antagonistic combinations of particulate matter and metals to determine their effect on the induction of ROS in human lung epithelial cells A549.The results showed that antagonistic effects between most particulate matter and metal combinations(F>5,P<0.05),which was consistent with the test results of cell viability.That is,particulate matter may have the impact on heavy metal toxicity through the ROS pathway.However,the changes of intracellular ROS in some combinations cannot fully explain the results of cell viability,and it was speculated that there may be other mechanisms that affect the toxic effects of PM,and further research is still needed in the future.