Short-term effect of sulfur dioxide (SO 2 ) change on the risk of tuberculosis outpatient visits in 16 cities of Anhui Province, China: the first multi-city study to explore differences in occupational patients

A growing number of biological studies suggest that exogenous sulfur dioxide (SO 2 ) at a certain concentration may promote human resistance to Mycobacterium tuberculosis . However, the results of most relevant studies are inconsistent, and few studies have explored the relationship between SO 2 exposure and tuberculosis risk at provincial level. In addition, occupational exposure has long been considered to have a certain impact on the human body, so for the first time, we discussed the differences between different occupations in the study on the relationship between air pollutant exposure and tuberculosis risk, and evaluated the impact of occupational exposure. This study aimed to explore the association between short-term SO 2 exposure and the risk of outpatient visits to tuberculosis in Anhui province and 16 prefecture-level cities from 2015 to 2020. We used several models for multi-stage analysis, including distributed lag nonlinear model (DLNM), Poisson generalized linear regression model, and random-effects model. The association was assessed using the 28-day cumulative lag effect RR and 95%CI for each 10-unit increase in SO 2 concentration. We divided all patients into the following six occupations: Worker, Farmer, Retired people, Children and Students, Cadre and Office clerk, and Service staff (catering, business, etc.). Sex, age, and season were analyzed by subgroup. Finally, the robustness of the multi-pollutant model was tested. At provincial level, the overall effect value of SO 2 was RR=0.8191 (95%CI: 07702~0.8712); after grouping all patients by occupation, the association found only among Farmers (RR = 0.7150, 95%CI: 0.6699–0.7632, lag 0–28 days) and Workers (RR = 0.8566, 95%CI: 0.7930–0.9930, lag 0–4 days) was still statistically significant. Estimates for individual cities and using random-effects models to estimate average associations showed that SO 2 exposure was associated with a reduced risk of outpatient TB visits in 14 municipalities, which remained significant when aggregated (RR = 0.9030, 95%CI: 0.8730–0.9340). Analysis of patients grouped by occupation in each municipality showed that statistical significance was again observed only in the Farmer (RR = 0.8880, 95%CI: 0.8610–0.9160) and Worker (RR = 0.8250, 95%CI: 0.7290–0.9340) groups. Stratified analysis of age, sex, and season showed that the effect of SO 2 exposure was greater for middle-aged people (18–64 years old) and males, and less for seasonal changes. In summary, we found that exposure to SO 2 reduces the risk of outpatient visits to tuberculosis, with farmers and workers more susceptible to SO 2 . Gender and age had a greater impact on the risk of TB outpatient visits than seasonal variations.