Health and Regulatory Impacts of PM_2.5 From Wildland Fires for 2019-2024 in the US

In recent years the area of wildland fires has increased in the US and many regions have experienced extremely poor air quality due to smoke. We combine data for PM_2.5 (particulate matter with diameter <2.5 μm) with a satellite product to identify smoke-influenced days and associated PM_2.5 for 2019-2024 from air quality monitors covering 85% of the US population. Averaged across the US, smoke is present on 14.2% of all days and increases the daily mean PM_2.5 concentration on these days by 6.9 μg m^-3, with a maximum of 687 μg m^-3. For each region, we estimate the contribution of smoke PM_2.5 to emergency department visits (EDV) for asthma. While rural regions in the western US have the highest contributions of smoke to the PM_2.5 concentrations, larger metropolitan areas have a greater number of EDV from smoke due to greater populations. We next consider the impacts of smoke on compliance with the US annual standard for PM_2.5 (9.0 μg m^-3). Using data for 2022-2024, out of 807 of monitors studied 174 would not meet the standard, but in the absence of smoke, only 57 of these would not meet the standard. While observed annual PM_2.5 has shown no significant change over the past 6 years, we find a significant decline in PM_2.5 when the smoke contributions are excluded.