Erjia Ge1, Min Fan2, Hong Qiu3, Howard Hu4, Linwei Tian5, Xiaomeng Wang6, Guozhang Xu7, Xiaolin Wei8. 1. Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada. Electronic address: Erjia.ge@utoronto.ca. 2. Jockey Club School of Public Health & Primary Care, The Chinese University of Hong Kong, Hong Kong SAR, China. Electronic address: cainefm@gmail.com. 3. School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: qiuhong@hku.hk. 4. Dalla Lana School of Public Health, University of Toronto, Canada. Electronic address: howard.hu@utoronto.ca. 5. School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: linweit@hku.edu.hk. 6. Zhejiang Provincial Center for Disease Control and Prevention, Zhejiang Province, China. Electronic address: xmwang@cdc.zj.cn. 7. Ningbo Center for Disease Control and Prevention, Ningbo, China. Electronic address: xugz@nbcdc.org.cn. 8. Division of Clinical Public Health, and Institute of Health Policy, Management and Evaluation, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada. Electronic address: xiaolin.wei@utoronto.ca.
Abstract
BACKGROUND: Recent biochemical studies suggest that exogenous sulfur dioxide (SO2) at low concentrations may have been beneficial in inhibiting mycobacteria tuberculosis (TB) growth. However, there is a dearth of population-based studies. OBJECTIVES: To examine the association of ambient SO2 levels and initial TB outpatient visits. METHODS: In Ningbo, China, we collected all daily initial outpatient visits for TB and routinely air pollution monitoring data between January 2009 and December 2013. A time-series study was conducted by using generalized additive regression (GAM) with log-linear Poisson models to estimate the associations between daily initial TB outpatient visits and daily average concentration of SO2. Other traffic-related co-pollutants were adjusted. Sensitivity analyses were conducted to examine the relationship when 1% extreme SO2 concentrations excluded or if related to the early onsets of TB symptoms. RESULTS: SO2 concentrations in Ningbo were low with a daily average of 25 μg/m3 (i.e. 0.0089 ppm). Negative associations were identified between ambient SO2 concentrations and daily initial TB outpatient visits. A 10 μg/m3 increase in SO2 at lag3 and lag0-3 days were associated with -2.0% (95%CI, -3.2, -0.8) and -4.6% (95%CI, -6.8, -2.4) changes, respectively, in initial TB outpatient visits according to single-pollutant models. The negative association became stronger when nitrogen dioxide (NO2) or particulate matter with aerodynamic diameter less than 10 μm (PM10) was adjusted in two-pollutant models. This association was higher in males vs. females and in middle-aged adults vs. the elderly. We found a stronger negative association between SO2 concentration and the initial symptom occurrence. CONCLUSION: Short-term exposure to ambient SO2 was associated with reduced risk of initial TB outpatient visits, suggesting acute protective effects of low-level ambient SO2 exposure on bacteria-induced pulmonary infections.
BACKGROUND: Recent biochemical studies suggest that exogenous sulfur dioxide (SO2) at low concentrations may have been beneficial in inhibiting mycobacteria tuberculosis (TB) growth. However, there is a dearth of population-based studies. OBJECTIVES: To examine the association of ambient SO2 levels and initial TB outpatient visits. METHODS: In Ningbo, China, we collected all daily initial outpatient visits for TB and routinely air pollution monitoring data between January 2009 and December 2013. A time-series study was conducted by using generalized additive regression (GAM) with log-linear Poisson models to estimate the associations between daily initial TB outpatient visits and daily average concentration of SO2. Other traffic-related co-pollutants were adjusted. Sensitivity analyses were conducted to examine the relationship when 1% extreme SO2 concentrations excluded or if related to the early onsets of TB symptoms. RESULTS:SO2 concentrations in Ningbo were low with a daily average of 25 μg/m3 (i.e. 0.0089 ppm). Negative associations were identified between ambient SO2 concentrations and daily initial TB outpatient visits. A 10 μg/m3 increase in SO2 at lag3 and lag0-3 days were associated with -2.0% (95%CI, -3.2, -0.8) and -4.6% (95%CI, -6.8, -2.4) changes, respectively, in initial TB outpatient visits according to single-pollutant models. The negative association became stronger when nitrogen dioxide (NO2) or particulate matter with aerodynamic diameter less than 10 μm (PM10) was adjusted in two-pollutant models. This association was higher in males vs. females and in middle-aged adults vs. the elderly. We found a stronger negative association between SO2 concentration and the initial symptom occurrence. CONCLUSION: Short-term exposure to ambient SO2 was associated with reduced risk of initial TB outpatient visits, suggesting acute protective effects of low-level ambient SO2 exposure on bacteria-induced pulmonary infections.