Smith, GS; Van Den Eeden, SK; Garcia, C; Shan, J; Baxter, R; Herring, AH; Richardson, DB; Van Rie, A; Emch, M; Gammon, MD
BACKGROUND: Ecologic analyses, case-case comparisons, and animal experiments suggest positive associations between air pollution and tuberculosis.
OBJECTIVES: We evaluated this hypothesis in a large sample which yields results more applicable to the general population.
METHODS: We conducted a case-control study nested within a cohort of Kaiser Permanente of Northern California members. All active pulmonary tuberculosis (TB) cases newly diagnosed from 1996-2010 (n=2309) were matched to two controls (n=4604) by age, gender, and race/ethnicity on the index date corresponding with the case diagnosis date. Average individual-level concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and particulate matter with aerodynamic diameter <2.5µm (PM2.5) and 10µm (PM10) for two years prior to diagnosis/entry into the study were estimated using measurements from the California Air Resources Board monitor closest to the subject's residence.
RESULTS: In single-pollutant adjusted conditional logistic regression models the pulmonary TB odds ratios (95% confidence interval) for the highest quintile (vs. lowest) were 1.50 (1.15, 1.95) for CO and 1.42 (1.10, 1.84) for NO2. Corresponding estimates were higher among never ((1.68 (1.26, 2.24) than ever smokers (1.19 (0.74, 1.92)) for CO. In contrast, for NO2, estimates were higher among ever (1.81 (1.13, 2.91)) than never smokers (1.29 (0.97, 1.71)). O3 was inversely associated for smokers (0.66 (0.43, 1.02)) and never smokers (0.65 (0.52, 0.81)). No other consistent patterns were observed.
CONCLUSIONS: In this first U.S. nested case-control study on air pollution and pulmonary TB to our knowledge, we observed positive associations with ambient CO and NO2, which require confirmation.
