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Wildfire smoke has reversed US progress toward ozone air quality, study finds
TL;DR
Recent research shows that wildfires in the US have reversed progress toward ozone air quality standards, significantly increasing emissions and contributing to tens of thousands of premature deaths. The study highlights that despite reduced emissions from other sources, ground-level ozone levels have plateaued since 2015 due to wildfire smoke.
Key points
- Wildfires have reversed US progress toward ozone air quality standards
- Increased emissions linked to tens of thousands of premature deaths
- Ground-level ozone levels have plateaued since 2015
- Wildfires contribute to ozone formation by emitting carbon monoxide and other gases
- Study published in Science highlights the correlation between wildfire emissions and health impacts
The highly destructive wildfires that have battered the US and North America in recent years have significantly increased emissions and been linked to tens of thousands of premature deaths, but their impact on air quality is greater than previously known, according to new research.
A study published in Science on Thursday found that, since 2015, wildfires have reversed US progress toward ozone air quality standards, as the worsening pollution caused by wildfire smoke has undone years of efforts to reduce emissions. Ground-level ozone (O3) is created when pollutants from cars, refineries and industrial sources reacts with sunlight, according to the Environmental Protection Agency.
Wildfires also create their own massive ozone problem as they emit carbon monoxide and other gases that can contribute to the formation of ozone, and smoke, which can spread far beyond the source of a fire, can lead to increasing ozone hundreds of miles away.
“Despite regulated reductions in anthropogenic emissions of O3 precursors, observation stations indicate that policy-relevant surface O3 levels have plateaued,” Weizhi Deng and other authors wrote. In other words, despite emissions of the chemicals that create ozone pollution going down, the amount of ground-level ozone has stopped declining*.* The study links this plateau to wildfire emissions and finds that the rise in O3 emissions is correlated with premature deaths, some 318 each year since 2013.
Homes burn above Pacific Coast Highway during the Palisades fire on 8 January 2025, in California Photograph: MediaNews Group/Orange County Register/Getty Images
There were limited ground measurements available to researchers as the US Environmental Protection Agency’s monitoring stations cover only 2% of land in the continental US, the study noted.
But researchers developed a data set by evaluating information from satellites and the EPA as well as meteorological data with deep learning models. They ultimately found that 03 went from decreasing by 0.65 parts per bn (ppb) per year before 2015 to rising 0.13 ppb annually after that year.
Wildfires are worsening around the world with global heating leading to extreme blazes and causing billions of dollars in damage and catastrophic loss of life. Canada and the American west have seen particularly devastating fires in recent years.
Q&A
How have wildfires affected ozone air quality in the US?
Wildfires have reversed progress toward ozone air quality standards by significantly increasing emissions, leading to a plateau in ground-level ozone levels since 2015.
What are the health impacts of wildfire smoke on air quality?
Wildfire smoke is linked to approximately 318 premature deaths each year since 2013, exacerbating air quality issues and increasing ozone pollution.
What causes ground-level ozone pollution?
Ground-level ozone is formed when pollutants from vehicles and industrial sources react with sunlight, and wildfires contribute additional emissions that worsen this pollution.
What does the recent study published in Science reveal about wildfires?
The study reveals that emissions from wildfires have significantly impacted air quality, reversing years of progress in reducing ozone pollution in the US.
