Wildland Fire–Related Smoke PM2.5 and Cardiovascular Disease Emergency Department Visits in the Western United States

Background

The impact of short‐term exposure to fine particulate matter with a diameter ≤2.5 μm (PM_2.5) due to wildland fire smoke on the risk of cardiovascular disease (CVD) remains unclear. We investigated the association between short‐term exposure to wildfire smoke PM_2.5 and emergency department visits for acute CVD in the western United States from 2007 to 2018.

Methods

We analyzed 49 759 958 emergency department visits for primary or secondary diagnoses of atrial fibrillation (AF), acute myocardial infarction, heart failure, stroke, and total CVD across 5 states. Daily smoke, nonsmoke, and total PM_2.5 were estimated using a 1‐km resolution satellite‐driven multistage model and were aggregated to the zip code level. A case‐crossover study design was used, adjusting for temperature, relative humidity, and day of the year.

Results

The mean smoke PM_2.5 was 1.27 (interquartile range, 0–1.29) μg/m³. A 10‐μg/m³ increase in smoke PM_2.5 was associated with a minuscule decreased risk for AF (odds ratio, 0.994 [95% CI, 0.991–0.997]), heart failure (odds ratio, 0.995 [95% CI, 0.992–0.998]), and CVD (odds ratio, 0.997 [95% CI, 0.996–0.998]) but not for acute myocardial infarction and stroke. Adjusting for nonsmoke PM_2.5 did not alter these associations. A 10‐μg/m³ increase in total PM_2.5 was linked to a small increased risk for all outcomes except stroke (odds ratio for CVD, 1.006 [95% CI, 1.006–1.007]). Associations were similar across sex and age groups.

Conclusions

Short‐term wildfire smoke PM_2.5 exposure was unexpectedly associated with a slightly lower risk of CVD emergency department visits. Whether these findings are due to methodological issues, behavioral changes, or other factors requires further investigation.