Association of Short-Term Increases in Ambient Fine Particulate Matter With Hospitalization for Asthma or COPD During Wildfire Season and Other Time Periods.

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.