The Effect Of Coarse Particulate Matter (PM_2.5-10) On Hospital Admissions For Lower Respiratory Tract Infection: A Case-crossover Study In Shi Jiazhuang

Objective : With the rapid development of urban construction,industrialization,and air pollution has become a threat to human health,which has aroused substantial attention of the world.Atmospheric Particulate Matter（Particulate Matter,PM）in size 10 microns or less particles known as Particulate Matter（PM10）,because it can enter the human respiratory tract and not easily to be educted to outside body,which also impairs the health of human body,which has caused more attention in humans.According to the aerodynamic equivalent diameter,it can be divided into different coarse particulate matter(PM_2.5-10),fine particulate matter(PM_2.5),and ultrafine particles（PM0.1）.Different-sized particles have obvious chemical composition differences.Coarse particles were generated by mechanical polishing and re-suspension of solid material,and its composition is mostly related to the soil and crustal composition.Fine particulate matter produced in the combustion or atmospheric photochemistry reaction,which mainly contains substances related to fuel combustion.Therefore,there are very evident difference between coarse particles and fine particulate matter in the effect on the body.At present,researches from home and abroad mainly focused on the influence of fine particulate matter,while for the coarse particles related epidemiological studies are limited,and the research results are divergent.Lower respiratory tract infection（LRTI）which includes communityacquired pneumonia,acute exacerbations of chronic obstructive pulmonary disease and acute exacerbations of bronchiectasis is the main reason for respiratory disease.Numerous epidemiological studies from home and abroad have been published on risks associated with PM.More recent work and evidence has been focused on PM_2.5 which has an association with mortality and morbidity.While researches on the health effects of PM_2.5-10 is limited and findings are different.Currently there is no research on the effects of coarse particles to the lower respiratory tract infection in hospital.Collecting data of air pollution in Shijiazhuang downtown during Jan 1st,2013 to 31 st Dec 2013,in the meantime doing the statistical report for city’s nine clinical data of hospitalized patients that caused by lower respiratory tract infection.Through the cases of two-way crossover study of statistical methods,analysing Shijiazhuang lower respiratory tract infection in hospital and the correlation of coarse particles in the atmosphere in the same period,to explore the coarse particles in atmosphere has caused the influence of the lower respiratory tract infection in hospital.Methods:1 Acquisition from 9 general hospitals of respiratory patients with lower respiratory tract infection in hospital information,（gender,age,length of hospital stay,merging,disease,etc.）day by day in Shijiazhuang,the time interval for the Jan 1st,2013 to Dec 31 st,2013.Lower respiratory tract infections include: bronchiectasis,chronic obstructive pulmonary disease,community-acquired pneumonia.2 Record on the Shijiazhuang atmospheric pollutants monitoring data from Jan 1st,2013 to Dec 31 st,2013,which includes 6 kinds of atmospheric pollutants: fine particulate matter(PM_2.5),particulate matter（PM10）,nitrogen dioxide（NO₂）,ozone（O₃）,sulfur dioxide（SO₂）and carbon monoxide（CO）monitoring value（from China’s environmental monitoring station site）.The coarse particles PM_2.5-10 data was calculated by the difference of PM 2.5 and PM 10.At the same time collecting Shijiazhuang daily average temperature during this period.3 We used a bidirectional case-crossover design to assess the risk of hospital admissions for lower respiratory tract infection for acute conditions based on exposure to various pollutants.We used the time-stratified approach to select control days.Air pollution levels on the dates of hospital admissions were compared with air pollutant levels one week before and one week after the date of admission.To assess pollution exposure,same-day average exposures and lagged intervals extending from 1 to 5 days before the case or control event were obtained.All statistical analyses were performed using the SPSS 17.0 package.The associations between hospital admissions for lower respiratory tract infection and levels of PM_2.5-10 were estimated using the odds ratio（OR）and corresponding 95% confidence intervals（95% CI）which were produced using conditional logistic regression with weights equal to the number of hospital admissions on that day.All models included daily weather variables.Both single-pollutant models and multi-pollutant models were fitted with a different combination of pollutants to assess the stability of the effect of PM_2.5-10.Stratified analyses of exposure based on the average exposure based on age,gender,complications and season were undertaken to evaluate effect modification.All statistical analyses were performed using the SPSS17.0 package,all statistical tests were two-sided.Values of P<0.05 were considered statistically significant.Results:1 During the study period,3126 admissions for lower respiratory tract infection were recorded.The majority were men（54.22%）and older（59.15%）.And 69.35 % of the admissions for lower respiratory tract infection were combined diabetes,hypertensive,heart disease,and so on.2 The data of air pollutants reveals that the mean annual concentration of PM_2.5,PM10,PM_2.5-10,SO₂,NO₂,CO and O₃ were（156.43±118.60）μg/m3,（311.26±162.94）μg/m3,（153.28±79.446）μg/m3,（106.44±86.84）μg/m3,（68.77±28.69）μg/m3,（2.04±1.74）mg/m3,（96.25±67.99）μg/m3.The mean annual concentration average level of pollutants were significantly higher compared with current Chinese national secondary standard.Particulate matter were the main pollutants in Shi Jiazhuang.3 For the single-pollutant model,lower respiratory tract infection admissions were positively associated with higher PM_2.5-10 levels at lag5.After adjusted for daily average temperature factor,a 10μg/m3 increase in PM_2.5-10 was associated with a 0.9% increase in hospital admissions for lower respiratory tract infection at lag 5（P<0.05）.4 We also considered effect modified by age,sex,season,and underlying disease.Increase in PM_2.5-10 was associated with increase in hospital admissions for lower respiratory tract infection,and a larger association was seen in male,elders and admissions with underlying disease（P<0.05）,which was much obvious in the cold season.5 For multi-pollutant models,when adjusted for PM_2.5,CO,NO₂,SO₂,PM_2.5+CO,PM_2.5 +NO₂,PM_2.5+SO₂,PM_2.5+O₃,PM_2.5+CO+NO₂+SO₂+O₃,the association of PM_2.5-10 with lower respiratory tract infection admissions was no longer statistically significant（P>0.05）.There were no statistically significant associations between coarse particulates and hospital admissions for lower respiratory tract infection after adjusted for other pollutants.Conclusion:After adjustment for PM_2.5,SO₂,NO₂,CO and O₃,there were no statistically significant associations between coarse particulates and hospital admissions for lower respiratory tract infection.