Association of Short-Term Increases in Ambient Fine Particulate Matter With Hospitalization for Asthma or COPD During Wildfire Season and Other Time Periods
Benjamin D. Horne, Mary M. Johnson, Denitza Blagev, François Haddad, Kirk U. Knowlton, Daniel Bride, Tami L. Bair, Elizabeth A. Joy, Kari C. Nadeau
Abstract
Background Short-term increases in air pollution are associated with poor asthma and COPD outcomes. Short-term elevations in fine particulate matter (PM 2.5 ) due to wildfire smoke are becoming more common. Research Question Are short-term increases in PM 2.5 and ozone in wildfire season and in winter inversion season associated with a composite of emergency or inpatient hospitalization for asthma and COPD? Study Design and Methods Case-crossover analyses evaluated 63,976 and 18,514 patients hospitalized for primary discharge diagnoses of asthma and COPD, respectively, between January 1999 and March 2022. Patients resided on Utah's Wasatch Front where PM 2.5 and ozone were measured by Environmental Protection Agency-based monitors. ORs were calculated using Poisson regression adjusted for weather variables. Results Asthma risk increased on the same day that PM 2.5 increased during wildfire season (OR, 1.057 per +10 μg/m 3 ; 95% CI, 1.019-1.097; P = .003) and winter inversions (OR, 1.023 per +10 μg/m 3 ; 95% CI, 1.010-1.037; P = .0004). Risk decreased after 1 week, but during wildfire season risk rebounded at a 4-week lag (OR, 1.098 per +10 μg/m 3 ; 95% CI, 1.033-1.167). Asthma risk for adults during wildfire season was highest in the first 3 days after PM 2.5 increases, but for children, the highest risk was delayed by 3 to 4 weeks. PM 2.5 exposure was weakly associated with COPD hospitalization. Ozone exposure was not associated with elevated risks. Interpretation In a large urban population, short-term increases in PM 2.5 during wildfire season were associated with asthma hospitalization, and the effect sizes were greater than for PM 2.5 during inversion season.