Impacts Of Air Pollutants And Meteorological Factors On Outpatient Visits For Respiratory Diseases

Background: With the background of air pollutions and frequent extreme weather events,the impacts of air pollution and climate change on human health,especially on the respiratory system,have received extensive attention.The respiratory system is a system that exposure directly with the outside ambient,it is more susceptible to the external environment.There are few reports on the exposure response,lagged effects and cumulative effects of pollutants and meteorological factors on respiratory diseases in Lanzhou.Objectives: The aim of this research is to study the changes of air pollution,meteorological factors and respiratory disease outpatient visits in Lanzhou,estimate the effects of air pollution and meteorological factors on visits,and provide scientific evidence for evaluating the health effects of air pollution and disease prevention.Methods: We obtained admission records for respiratory diseases(from 1 January 2007 to31 December 2016)from the first hospitals of Lanzhou University,and the air pollutants and meteorological data were collected.The effects of air pollution and meteorological factors on the number of respiratory disease outpatients,the lag effect and cumulative effect were analyzed by the distribution lag nonlinear model(DLNM).Stratified study was conducted according to gender and age.Results:(1)The PM2.5 concentration,NO2 concentration,ambient temperature and relative humidity in Lanzhou City all had obvious seasonality.The PM2.5 concentration showed a decreasing trend in the past 5 years,and the average daily temperature and respiratory disease outpatient visits in the past 10 years increase yearly.(2)There were 509,275 patients who were admitted to the hospital because of respiratory diseases,with a male-to-female sex ratio 1.19,0-5 years old accounted for 52.94% of the visits,and there were an average of 139 daily respiratory diseases over the study period.(3)There was a statistically significant correlation between PM2.5,NO2,ambient temperature and relative humidity and respiratory disease outpatient visits(P<0.01).(4)The concentrations of PM2.5 and NO2 were positively correlated with the number of visits to respiratory diseases.The maximum number of visits was 100 μg/m3.There was a “M” type of exposure reaction between the temperature and the number of visits,and the number of visits increased at a lower and higher temperature.Exposure at lower relative humidity outpatient visits increased significantly,for patients aged 6-17 years,18-59 years and ≥ 60 years exposed to higher relative humidity the visits increased.(5)Lag effects:The days of lag for PM2.5 affecting disease were days 1,2 and 6-13;for NO2 were days 0-2 and 5-10;the days of lag for low temperatures were 0-2 days and 7-9 days,for high temperature were 0-3 days,for low relative humidity were 0-3 days and for high relative humidity were 7-14 days.(6)Cumulative effects:Exposed to high concentration of PM2.5,the cumulative 0-14 days clinic visits reached the peak.Exposure to high concentration of NO2,the cumulative 0-10 days visits reached the peak.At different temperature,the cumulative 0-7 days clinic visits reached the peak.At low relative humidity,the cumulative days was 0-7,at high relative humidity,it was 0-14.Conclusions: PM2.5,NO2,ambient temperature and relative humidity all have obvious seasonality and are related to outpatient visits.There are obvious lag effects and cumulative effects.The effects are different in different ages and gender groups.