The Influence Of Air Pollutants On The Outpatient Quantity Of Respiratory Diseases In Xi’an And The Mechanism Of Susceptibility Of PM_2.5 To Pneumonia

In recent years,with the continuous development of China’s economy and acceleration of the industrialization,air pollution,shortage of fresh water resources,ecological crisis,population sub-health and other issues are increasingly prominent,seriously affecting the quality of life of modern people.Among them,the impact of air pollution on human health is more intuitive and obvious,especially the adverse effect on human respiratory system and circulatory system.The impact of air pollution on population health varies from region to region due to the influence of respective regional economic and industrial structure,which means that the results of one region could not be simply copied to other parts of the country.So it is necessary and urgent to investigate the impact of air pollution on people health combined with regional features.This study set the relationship between air pollution and population health in xi’an as the research object and collected relevant data,including the daily data of six kinds of air pollutants in Xi’an from 2015 to 2016(PM_2.5and PM₁₀,CO,SO₂,NO₂and O₃),the daily meteorological data in Xi’an from 2015 to 2016（average temperature,daily average relative humidity and daily average air pressure,wind speed）,and the daily outpatient and emergency data of respiratory departments of two comprehensive 3a grade hospitals in Xi’an during the same period.Spearman’s rank correlation test was used to evaluate the correlation between air pollutants and meteorological factors during the same period.A smooth spline function was used to control the influence of daily mean temperature,relative humidity,air pressure and long-term trend on the outpatient volume of respiratory diseases.The Day of the Week effect（DOW）was incorporated into the multivariate regression model as a dummy variable.Considering the lag effect of 0 to 7days,this paper adopted the Generalized Additive Model（GAM）taking Poisson distribution as the connection function.Through the construction of single pollutant and multipollutant models and the analysis of age and disease subgroups,the influence of air pollutants on the number of outpatient and emergency visits of respiratory diseases and categories and features of respiratory diseases were studied.This paper explained the specific effect of air pollutants on population health in Xi’an.The main findings are as follows:（1）There was a significant correlation between the concentration of air pollutants in Xi’an from 2015 to 2016 and the local meteorological factors during the same period.（2）During the study period,the concentrations of PM_2.5,PM₁₀and NO₂in xi’an exceeded the national standards,and the average daily concentrations of PM_2.5and PM₁₀exceeded the national standards by two times,indicating that the air pollution in Xi’an was in the mid high level,and the particulate pollution was more serious.（3）Under the single pollutant model,it is found that the concentration changes of air pollutants PM_2.5,PM₁₀,SO₂,NO₂and CO in Xi’an have a great influence on the outpatient visits of respiratory diseases,combined with the previous domestic researches,this paper think the CO is an independent risk factor for respiratory disease in Xi’an.（4）Under the multi-pollution model,it was found that the air pollutants in Xi’an had the greatest influence on the outpatient visits of asthma and chronic obstructive pulmonary disease（COPD）among respiratory diseases.（5）Animal experiments showed that PM_2.5exposure weakened the bacterial clearance ability of macrophages in rats,and reduced the defense function of the host,which made the body exposed to PM_2.5more susceptible to pneumonia under the same pathogenic conditions.Conclusion:The changes of the concentration of six atmospheric pollutants in Xi’an have a certain influence on outpatient and emergency visits of respiratory diseases,and the pollutant CO has the greatest influence.Under the analysis of multi-pollution model,the pollutants have the greatest influence on outpatient visits of asthma and COPD,significantly increased outpatient visits for COPD and asthma;Exposure to PM_2.5could increase the susceptibility of the host to pneumonia,mainly due to the decreased function of the host macrophages caused by PM_2.5and the following decreased ability to remove bacteria.