Summertime Trends in U.S. Population Exposure to Fine Particulate Air Pollution (PM_2.5) from Wildfire Smoke

This work documents trends in summertime fine particulate matter (PM2.5) concentrations across the continental United States, daily PM2.5 concentrations that exceed health-based recommendations set by the U.S. Environmental Protection Agency, and population-based exposures during the June–October wildfire season for the years 2000–2023. The major finding of this work is that summertime PM2.5 events due to wildland fire smoke (originating from both inside and outside the United States) regularly exceed health-based, air quality index levels with a frequency and a magnitude that rival those of pollution events prior to the U.S. National Ambient Air Quality Standard revisions of 2006 and 2012. The year 2023 was the worst year on record this century for hazardous air pollution days in the continental United States. Wildland fire smoke is a largely uncontrollable source of air pollution with public health costs that are real and increasing in magnitude.