Differential Effects Of Wintertime PM_2.5 From Shanxi And California On Young Healthy Mice

Airborne particulate matter?PM?is a global concern because exposure is associated with adverse effects on the cardiorespiratory system,such as asthma,COPD,and myocardial infarction.Worldwide air pollution related annual mortalities have been estimated at 7 million.PM has a wide variety of physicochemical characteristics,in which fine PM,also known as PM_2.5?Dp ? 2.5 ?m?,is especially harmful because it can readily deposit deep in the lung and be retained,irritating lung parenchyma or moving into the blood stream.Therefore,PM_2.5 has become a hot topic of global concern.To investigate the mechanism of PM_2.5 toxicity will provide strong scientific evidence that highlight a need to develop source-specific regulations that support greater protection of human health.In this study,PM was collected in the capital cities of Shanxi Province and the state of California,Taiyuan and Sacramento,respectively,based on the fact that both cities are heavily urbanized,have relatively dry,sunny winters,economies dominated by agriculture and industry,and a long history of unhealthy levels of PM_2.5,especially during the winter season.PM pollution has increased with industrialization and rapid economic growth fueled by fossil fuels.Because the economy of Taiyuan is dominated by industry and agriculture related to abundant coal production and combustion,while the economy of Sacramento is largely based on transportation and agriculture,it was expected that the study would provide an opportunity to better understand how PM source influences pulmonary toxicity.To compare the biological effects of the two geographic PM samples,thirty 8-week-old were divided into three groups and were exposed to the collected PM_2.5 from Shanxi or California by oropharyngeal aspiration on an equal mass basis.Animals were sacrificed 24 hours post-exposure and patterns of pulmonary toxicity were assessed by bronchoalveolar lavage?BAL?,enzyme-linked immunosorbent assays?ELISA?and histopathologic assessment.The results show that both experimental groups have more neutrophils,chemokines and cytokines expression and visible inflammatory cells in histological lung section compared to control group.Additionally,California PM was associated with significantly increased neutrophil numbers and CXCL-1 and TNF-a protein levels compared to the Shanxi PM.Chemical analyses were performed with both the two PM samples.Results suggest that both PM samples consisted primarily of organic compounds,while the California PM sample was more oxidized.Another major difference was that Shanxi PM had a much higher percent of sulfate,whereas California PM had a much greater percent of nitrate.In addition,there was a notable differences in metals concentration between the two PM samples included the following:higher calcium,magnesium,barium,lead in Shanxi PM but higher copper in California PM.Based on the differences of pulmonary inflammation and the chemical composition between the two PM experimental groups,the study reveals the chemical differences could help explain potential differences in pulmonary toxicity.The greater biological inflammatory response could be due to its higher oxidized state and metal concentration.