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Abstract Long‐term declines in concentrations of fine particulate matter (PM2.5) in the United States (U.S.) have been disrupted in recent years, with recent trends stagnating or reversing. In this study, we analyze surface observations of PM2.5composition from 2002 to 2022 to identify the chemical components driving this shift. We find that PM2.5concentrations plateau across seasons and regions in the contiguous U.S. since 2016, even after excluding estimated wildfire impacts, suggesting that the rise in wildfire activity alone does not account for these trends. The stagnation is primarily driven by a slowdown in the reduction of sulfate and a non‐significant increase in organic aerosols. In the Eastern and Central U.S., sulfate concentrations generally mirror decreasing anthropogenic SO2emissions, except in winter, where chemical feedbacks related to oxidant limitations weaken the response of sulfate. We find that nitrate and NO2concentrations decrease slower than anthropogenic nitrogen oxides (NOx) emissions, particularly in fall and winter, suggesting a potential overestimate in the decrease of NOxemissions in the U.S. Environmental Protection Agency National Emission Inventory (NEI) and/or an increasing role of natural and non‐U.S. sources. In the Southeast, the decline in organic aerosol concentrations has stalled since 2015, possibly due to weaker decreases in sulfate‐induced secondary organic aerosol (SOA) formation from isoprene, combined with increases in monoterpene‐derived SOA as the climate warms. Despite continued decreases in the NEI black carbon (BC) emissions, BC concentrations have stagnated since 2015, even after removing the estimated influence of wildfire smoke, indicating a possible underestimate in emissions.
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This content will become publicly available on January 23, 2027
Ambient air quality and health impacts of PM2.5 from US residential wood combustion
Residential wood combustion (RWC) is a primary heating fuel in just 2% of US homes. However, the 2023 release of the US Environmental Protection Agency’s National Emissions Inventory (NEI) found that RWC contributes ~28% of total wintertime fine particulate matter (PM2.5) emissions, suggesting that ambient PM2.5concentrations could be substantially reduced if RWC were curtailed. Despite its contribution to PM2.5emissions, an assessment of the air quality, health, and distributional impacts of RWC using the updated NEI has not been performed. Here, we use a high-resolution (4 kilometers) air quality model and the updated NEI to evaluate wintertime RWC impacts over the contiguous United States. We find that RWC contributes 2.43 micrograms per cubic meter (21.9%) of winter population-weighted mean PM2.5concentrations, leading to ~8600 (confidence interval: 6500 to 9600) premature deaths annually. Moreover, nonwhite communities are disproportionately affected by RWC-related PM2.5and associated mortality, especially in urban areas. We suggest that policies targeting RWC could substantially reduce air pollution, improve health, and address distributional disparities.
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- Award ID(s):
- 2239834
- PAR ID:
- 10692090
- Publisher / Repository:
- AAAS
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 12
- Issue:
- 4
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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