Tuberculosis Diagnoses Following Wildfire Smoke Exposure in California

Abstract Rationale Wildfires are a significant cause of exposure to ambient air pollution in the United States and other settings. Although indoor air pollution is a known contributor to tuberculosis reactivation and progression, it is unclear whether ambient pollution exposures, including wildfire smoke, similarly increase risk. Objectives To determine whether tuberculosis diagnosis was associated with recent exposure to acute outdoor air pollution events, including those caused by wildfire smoke. Methods We conducted a case-crossover analysis of 6,238 patients aged ≥15 years diagnosed with active tuberculosis disease between 2014 and 2019 in 8 California counties. Using geocoded address data, we characterized individuals’ daily exposure to <2.5 μm-diameter particulate matter (PM2.5) during counterfactual risk periods 3–6 months before tuberculosis diagnosis (hazard period) and the same time 1 year previously (control period). We compared the frequency of residential PM2.5 exposures exceeding 35 μg/m3 (PM2.5 events) overall and for wildfire-associated and nonwildfire events during individuals’ hazard and control periods. Measurements and Main Results In total, 3,139 patients experienced 1 or more PM2.5 events during the hazard period, including 671 experiencing 1 or more wildfire-associated events. Adjusted odds of tuberculosis diagnosis increased by 5% (95% confidence interval, 3–6%) with each PM2.5 event experienced over the 6-month observation period. Each wildfire-associated PM2.5 event was associated with 23% (19–28%) higher odds of tuberculosis diagnosis in this time window, whereas no association was apparent for nonwildfire-associated events. Conclusions Residential exposure to wildfire-associated ambient air pollution is associated with an increased risk of active tuberculosis diagnosis.