Short-Term Effect Of Air Pollutant Change On The Risk Of Tuberculosis Outpatient Visits In Sixteen Cities Of Anhui Province,China

Objective:The World Health Organization’s Global Tuberculosis（TB）Report shows that there will be more than 10.6 million new cases and 1.6 million deaths from TB in 2021.Our aim was to investigate the association between short-term exposure to multiple air pollutants and the risk of TB outpatient visits in 16 cities of Anhui Province,China,during 2015-2020,while exploring differences among different populations to provide more evidence on the association between TB and air pollution.Method:Our case data were reported and collected by Anhui Tuberculosis Prevention and Control Institute through the subordinate department（municipal Center for Disease Control and Prevention）.Data on air pollutants were collected from environmental monitoring centers in various cities,and meteorological data were collected from China Meteorological Data Network.After establishing the provincial time series database,the Spearman rank correlation value was used to evaluate the association between air pollutants and meteorological factors.This study used a two-stage model analysis,including Distributed lag non-linear model（DLNM）and Random effects model,to assess the association between air pollutant exposure and TB risk.Associations were assessed using a 28-day cumulative lag effect（RR and 95%CI）for each 10-unit increase in air pollutant concentration,including estimates for individual cities and estimates of average associations using a random effects model.We stratified the analysis by sex and age.Age stratification was divided into<19 years old group,19-64 years old group and>64 years old group,and gender stratification was divided into male group and female group.Sensitivity analysis was then conducted,including the establishment of bi-exposure models.and changed the degrees of freedom of meteorological factors in the model（df4-6）,to test the stability of the results.Results:（1）Descriptive statistical analysis:From 2015 to 2020,there were 186,623 TB outpatients in Anhui Province.Among them,Hefei had the most cases（24,393 cases,accounting for 13.1%）.Huangshan had the least number of cases（4140 cases,accounting for 2.2%）.The average daily concentrations of PM_2.5,PM₁₀,SO₂ and O₃ in Anhui Province were 49.09μg/m3（3～213μg/m3）、75.91μg/m3（4～318μg/m3）、15.03μg/m3（6～52μg/m3）and 92.77μg/m3（0～220μg/m3）,respectively.The average daily minimum temperature of the province was-6.8℃,and the maximum temperature was 33.3℃.The lowest and highest daily relative humidity were 40%and 98%,respectively.The daily wind speed in the province ranged from 0.8 to 5.6 m/s.（2）Correlation analysis:The average correlations aggregated after using a random effects model of PM_2.5 and PM₁₀ were RR=1.031（95%CI:1.019-1.043）and RR=1.023（95%CI:1.016-1.030）,respectively.The city with the strongest correlation between PM_2.5 and TB outpatient risk was Tongling,with a relative risk of 1.1360（95%CI:1.0271-1.2583）,while the city with the strongest correlation between PM₁₀ was Suzhou,with a relative risk of 1.0629（95%CI:1.0421-1.0842）.Stratified analyses showed that the effects of particulate pollutants were more significant for men and the elderly,while there was little association between particulate pollutants and TB risk in children and adolescents.The results of O₃ exposure showed that the strongest correlation was found in Bozhou（RR=1.0684,95%CI:1.0256-1.1129）,and the results after model summary still showed that O₃ exposure would increase the risk of TB（RR=1.0230,95%CI:1.0160-1.0310）.Stratified analysis showed that the effect of O₃ exposure on the elderly was more significant,and we did not find a significant difference between male and female groups.Unlike the previous pollutants,we found the opposite effect of SO₂exposure on TB risk.Estimates for individual cities and the average correlations estimated using a random effects model showed that SO₂ exposure was associated with a reduced risk of TB outpatient visits in 14 cities and the results were still significant（RR=0.9030,95%CI:0.8730-0.9340）after model summary.Stratified analyses by age and sex showed that SO₂ exposure had a greater effect on middle-aged people（19-64years）and men.（3）Sensitivity analysis:By changing the degree of freedom of meteorological factors in the model and establishing the bi-exposure model,the results of each pollutant only changed slightly,indicating the robustness of the research results.Conclusion:The results of this study showed that exposure to PM_2.5,PM₁₀,and O₃ were associated with an increased risk of TB outpatient visits,while exposure to SO₂ was associated with a decreased risk of TB outpatient visits.Subgroup analysis showed that air pollutant exposure had a greater effect on male,particulate pollutants exposure had a greater impact on the elderly,O₃ exposure had a more significant impact on the elderly,and SO₂ exposure had a greater impact on the middle-aged（19-64 years old）.Men and the elderly are vulnerable groups to TB,so different prevention and control strategies should be tailored to different populations and local air quality to reduce the burden of TB.