Ambient PM_2.5 exposure and tuberculosis reactivation: a cross-sectional study in an intermediate burden city

Hong Kong is an intermediate tuberculosis (TB) endemicity city dominated by reactivation diseases. A cross-sectional study on the clinical and epidemiologic data of newly diagnosed TB cases was conducted in such a setting, to examine the association between ambient PM_2.5 and TB reactivation. After the exclusion of cases most likely resulting from recent infection, four distinct TB population phenotypes were delineated by latent class analysis based on their reactivation risk and clinical profiles (N = 2,153): 'Elderly male' (26%), 'Otherwise healthy younger adult' (34%), 'Older female' (19%) and 'Male smoker' (21%). Overall, exposure to high concentrations of ambient PM_2.5 6 and 12 months before the notification was significantly associated with 'Otherwise healthy younger adults' membership (OR = 1.07 and 1.11, respectively) compared with 'Elderly male'. Such association was less evident for other phenotypes. The differential pattern of association between ambient PM_2.5 exposure and TB population phenotypes suggested the role of ambient PM_2.5 in TB reactivation.