Association of ambient PM_2.5 concentration with tuberculosis reactivation diseases—an integrated spatio-temporal analysis

Objectives: While the plausible role of ambient particulate matter (PM)_2.5 exposure in tuberculosis (TB) reactivation has been inferred from in vitro experiments, epidemiologic evidence is lacking. We examined the relationship between ambient PM_2.5 concentration and pulmonary TB (PTB) in an intermediate TB endemicity city dominated by reactivation diseases. Methods: Spatio-temporal analyses were performed on TB notification data and satellite-based annual mean PM_2.5 concentration in Hong Kong. A total of 52,623 PTB cases from 2005-2018 were mapped to over 400 subdistrict units. PTB standardized notification ratio by population subgroups (elderly aged ≥65, middle-aged 50-64, and young adults aged 15-49) was calculated and correlated with ambient PM_2.5 concentration. Results: Significant associations were detected between high ambient PM_2.5 concentration and increased PTB among the elderly. Such associations were stable to the adjustment for socio-economic factors and other criteria pollutants. Unstable patterns of association between PM_2.5 and PTB risk were observed in the middle-aged population and young adults, for which the observed associations were confounded by other criteria pollutants. Conclusion: With elderly PTB almost exclusively attributable to reactivation, our findings suggested that increased TB reactivations have occurred in association with high ambient PM_2.5 exposure, lending support to preventive measures that minimize PM_2.5-related TB reactivation.