D26-16 Wildfire Smoke and Total PM2.5 Associated With Higher Airway Inflammation in Black and Hispanic Adults With Moderate-to-severe Asthma

Introduction

Wildfires and fossil fuel combustion generate fine particulate matter (PM2.5), which is associated with asthma exacerbations and respiratory mortality. Few studies have evaluated whether wildfire smoke (WFS) PM2.5 is associated with airway inflammation in adults, and if so, whether associations differ compared to total PM2.5. Our aim was to determine the extent to which short-term exposure to WFS PM2.5 and total PM2.5 are associated with airway inflammation, measured by fractional exhaled nitric oxide (FeNO), in adults with asthma in the US.

Methods

Study participants were Black and Hispanic adults with moderate-to-severe asthma from the PeRson EmPowered Asthma RElief (PREPARE) cohort, a national randomized, open-label trial of Patient Activated Reliever-Triggered Inhaled Corticosteroids (PARTICS) that enrolled between 2017-2021. We excluded participants who lived outside the continental US and did not undergo FeNO testing, which was performed once at baseline. We assigned daily wildfire smoke PM2.5 and total PM2.5, temperature, and relative humidity to geocoded participant addresses. We evaluated associations of lags 1-7 days WFS PM2.5 and total PM2.5 with FeNO using linear regression. We log-transformed FeNO due to non-normality and report effect estimates as percent difference per 1 microgram per cubic meter (µg/m3) higher PM2.5. We adjusted for age, sex, body mass index, US region of testing, season, health literacy, current smoking status, relative humidity and mean temperature (same time window as exposure). We performed sensitivity analyses excluding smokers and limiting WFS analyses to non-zero WFS days. To assess whether associations between WFS PM2.5 and FeNO differed from that of total PM2.5, we conducted Ztests comparing effect sizes.

Results

We included 912 participants, 82.1% female, with mean (SD) age 48 (14) years, predominantly non-smokers (68%), 24.3% former smokers. For FeNO measurements with WFS in the preceding week, lag 1 day median (IQR) WFS PM2.5 was 1.6µg/m3 (3.1µg/m3). Median total PM2.5 was 6.5µg/m3 (3.9µg/m3). Median FeNO was 18ppb (22ppb). For every 1µg/m3 higher prior day WFS PM2.5, FeNO was a 5.1% (95% CI: 0.9%,9.4%) higher. Every 1µg/m3 increase in prior day PM2.5 was associated with a 3.3% (95% CI 1.5%,5.0%) higher FeNO. Associations were not statistically different for WFS PM2.5 vs. total PM2.5 with FeNO. Associations between WFS PM2.5 and FeNO were similar in direction and magnitude in sensitivity analyses excluding smokers and days without WFS.

Conclusions

In Black and Hispanic adults with moderate-to-severe asthma, acute exposures to low levels of wildfire-specific and total PM2.5 are associated with higher airway inflammation.

This abstract is funded by: NIH/NIEHS