The Influence Of The Interaction Between Air Pollutants And Temperature On Outpatient Volume Of Respiratory Diseases In A Hospital In Hohhot

Objective This study was conducted to assess the effect of air pollution and temperature on the respiratory health of the population in Hohhot by analyzing the association between air pollutants and their interaction with temperature and the number of respiratory outpatient visits in a hospital from 2019 to 2021.In order to provide a scientific basis for Hohhot to formulate air pollution prevention and control strategies,and accumulate basic data for the health risk assessment of air pollutants in arid-semi-arid areas of northern China.Methods In this study,daily average monitoring data of six conventional air pollutants and meteorological factors were collected in Hohhot from 2019 to 2021,while day-by-day outpatient data（date of visit,gender,age,primary diagnosis,etc.）were retrieved from a large tertiary general hospital in Hohhot.Based on time series research,a generalized additive model was established to quantify the single-day lag and cumulative average lag effect of air pollutants on the top three subtypes of respiratory diseases in total outpatient volume and number of visits,and stratified analysis（gender,age）.Then,the interaction terms between air pollutants and temperature were included in the model,and the influence of air pollutants and temperature on respiratory diseases and the outpatient volume of various subtypes was displayed through a three-dimensional map of two independent variables.Finally,the robustness of the model was verified by the two-pollutant model.Results（1）The total number of outpatient visits for respiratory diseases was 143,830 cases in a hospital in Hohhot from 2019 to 2021,of which72,226 and 22,127 were female and elderly（≥65 years old）patients,respectively.The annual average concentrations of PM_2.5and PM₁₀were 37.45±41.14μg/m³and 80.34±95.61μg/m³,respectively,which exceeded the national secondary standard.The mean concentrations of SO₂,NO₂,CO and O₃were 17.29±11.87μg/m³,28.63±18.16μg/m³,0.90±0.55mg/m³and 91.93±38.26μg/m³.Except for NO₂,whose concentration changed little throughout the year,other air pollutants showed certain seasonal fluctuations.Among them,O₃was high in summer and low in winter,and other pollutants showed a trend of high in winter and spring and low in summer（P<0.05）;（2）The lag time of the strongest effect of PM_2.5,PM₁₀,SO₂and O₃on respiratory disease outpatient volume was lag07,and the corresponding effect values（ER）were 2.08%（1.71%,2.44%）,0.51%（0.38%,0.65%）,4.70%（3.36%,6.06%）and-3.91%（-4.46%,-3.35%）,respectively,and lag06 for NO₂and CO,with ERs of 4.33%（3.36%, 5.30%）,13.90%（9.71%,18.28%）.The main groups affected were women and the elderly.（3）PM_2.5,PM₁₀,SO₂,NO₂,CO,and O₃had lagging effects on the top three subtypes of respiratory outpatient visits（rhinitis,asthma,and pharyngitis）.For rhinitis:every 10μg/m³increased in PM_2.5,PM₁₀,SO₂,NO₂,CO,and O₃（1mg/m³for CO）,the outpatient visits increased by 2.02%（1.23%,2.80%）,0.39%（0.13%,0.65%）,5.98%（3.90%,8.09%）,2.02%（0.69%,3.36%）,16.48%（7.25%,26.51%）,-4.21%（-5.19%,-3.23%）,respectively.Women,children and the elderly were the main groups affected.For asthma:the concentrations of PM_2.5,PM₁₀,SO₂,NO₂,CO and O₃increased,corresponding to the percentage changes in outpatient volume of 2.37%（1.33%,3.41%）,0.56%（0.21%,0.92%）,17.65%（13.98%,21.43%）,6.40%（3.43%,9.46%）,28.26%（12.98%,45.61%）and-1.92%（-3.17%,-0.67%）respectively.Women and children were disproportionately affected.For pharyngitis:PM_2.5,PM₁₀,SO₂,NO₂and CO showed the same hazard effect,men and children were susceptible groups.（4）Six pollutants and temperature had interactive effects on rhinitis,asthma and pharyngitis.For the peak of rhinitis outpatient volume:the greatest synergistic effect of the six pollutants was located in the low temperature period.For asthma:CO had the highest volume in asthma clinics at high-temperature and high concentration levels,and the greatest effects of other pollutants were located during periods of low temperatures.The interaction between PM_2.5,PM₁₀and air temperature on the outpatient volume of pharyngitis was peaked in the high temperature-high concentration daily average concentration pollutant mode,and the remaining pollutants were under low temperature-high concentration pollutants.Conclusion The mean PM_2.5and PM₁₀concentrations exceeded the national standard values in Hohhot in 2019-2022.The increase of PM_2.5,PM₁₀,SO₂,NO₂and CO concentrations was associated with the increase in the number of outpatient visits for respiratory diseases,rhinitis,asthma and pharyngitis.Six kinds of atmospheric pollutants and temperature had interaction effects on respiratory diseases,rhinitis,asthma and pharyngitis,and the interaction mode was different due to different air pollutants.