Examining the Short-Term Effect of Moderate Level Air Pollution on Multi-Department Outpatient Visits in Xi’an, China

Abstract Objective: There is limited evidence concerning the association between air pollution and outpatient visits in moderately polluted areas. This paper investigates the effects of moderate level ambient air pollution on the number of outpatient visits associated with five categories of medical conditions. Methods: We analyzed a total of 1,340,791 outpatient visits for five medical departments (pediatrics, respiratory, ENT, cardiovascular, and orthopedics) in Xi’an from 2016 to 2018. A distributed non-linear model was used to analyze the associations and was fitted and stratified by age and season. Results: We found 𝑆𝑂2 had the largest effect on pediatrics visits (RR=1.105 (1.090, 1.121)). The relationships among 𝑃𝑀2.5 and 𝑂3 and ENT were more statistically significant in a heating season than those in a non-heating season. Meanwhile, 𝑃𝑀2.5, 𝑃𝑀10, and 𝑆𝑂2 had bigger impacts on ENT visits for people under 50 years. The results showed a strong association between 𝑂3 and cardiovascular outpatient visits in a non-heating season (RR=1.026 (1.020,1.032)). The results also showed that 𝑃𝑀10 was not significantly associated with respiratory outpatient visits, and every 10 𝜇𝑔/𝑚3 increase of 𝑆𝑂2 reduced the number of respiratory outpatient visits by 3%. We found 𝑃𝑀2.5 and 𝑁𝑂2 were significantly related to orthopedic outpatient visits for people under 60.Conclusion: Our findings indicated short-term exposure to air pollutants had varying associations with outpatient visits to four medical departments. We also proposed a new set of air pollution thresholds, which could help hospitals optimize outpatient resource allocation and the government determine appropriate air quality standards.