Daily Local-Level Estimates of Ambient Wildfire Smoke PM_2.5 for the Contiguous US

Abstract

Smoke from wildfires is a growing health risk across the US. Understanding the spatial and temporal patterns of such exposure and its population health impacts requires separating smoke-driven pollutants from non-smoke pollutants and a long time series to quantify patterns and measure health impacts. We develop a parsimonious and accurate machine learning model of daily wildfire-driven PM 2.5 concentrations using a combination of ground, satellite, and reanalysis data sources that are easy to update. We apply our model across the contiguous US from 2006 to 2020, generating daily estimates of smoke PM 2.5 over a 10 km-by-10 km grid and use these data to characterize levels and trends in smoke PM 2.5 . Smoke contributions to daily PM 2.5 concentrations have increased by up to 5 μg/m 3 in the Western US over the last decade, reversing decades of policy-driven improvements in overall air quality, with concentrations growing fastest for higher income populations and predominantly Hispanic populations. The number of people in locations with at least 1 day of smoke PM 2.5 above 100 μg/m 3 per year has increased 27-fold over the last decade, including nearly 25 million people in 2020 alone. Our data set can bolster efforts to comprehensively understand the drivers and societal impacts of trends and extremes in wildfire smoke.

Wildfire influence on recent US pollution trends

“…Studies using data prior to 2016 concluded that the wildfire contribution to measured PM 2.5 concentrations was apparent mainly in the northwest of the contiguous US (CONUS), but disagreed over whether enhancements in this region were observable in average annual concentrations or only in extreme daily concentrations (5,6). Studies that include more recent data from the very active 2018 and 2020 wildfire seasons conclude that the imprint of wildfire smoke on surface average and extreme PM 2.5 concentrations has expanded substantially in geographic scope, with observed enhancements throughout much of the Western US (7,8). Research also suggests that wildfire smoke is increasingly implicated in "exceptional event" designations, or days on which regulators exempt observed pollutant concentrations from determination of regulatory attainment under the Clean Air Act because the source of the pollution was deemed beyond control of local authorities (9).…”

“…To isolate the contribution of wildfire smoke to pollution concentrations, we build on earlier work (6,8) and use a combination of ground-and satellite-based measurements to isolate the component of surface PM 2.5 concentrations attributable to wildfire smoke. Specifically, our primary analysis combines daily data from thousands of regulatory pollution monitoring stations from across the US with satellite-and analyst-based estimates of when and where wildfire smoke is in the air (Fig S1).…”

Air pollution is associated with lower levels of social movement participation, especially among well-resourced communities.

“…We also take two steps to explore whether the source of air pollution influences its impact on political participation. First, we leverage new data on particulate matter emissions from wildfires (Childs et al 2022). Pollution from wildfires may be especially likely to shape people's willingness to take political action.…”

Prescribed burns as a tool to mitigate future wildfire smoke exposure: Lessons for states and rural environmental justice communities

“…Given decades of successful air pollution regulations coupled with the dramatic increase in fire activity across the western United States (Abatzoglou and Williams, 2016), smoke particulate matter (PM2.5) from wildfires presents one of the greatest threats to air quality in the United States, especially in the West (Childs et al, 2022;Larsen et al, 2018). PM2.5 can penetrate deep into the lungs, leading to an array of health effects, including pulmonary disease, stroke, and premature death (Landguth et al, 2020;Liu et al, 2017).…”