Wildfires reverse decades of US progress on ozone pollution, causing 318 deaths annually

Wildfires Undo Decades of Air Quality Progress

The United States achieved remarkable success in reducing ozone pollution for over a decade, but that progress has been reversed since 2015 due to increasingly severe wildfires. A new study published in the journal Science reveals that national smog levels dropped by 11% from 2003 to 2015 as federal regulations on power plants, cars, and diesel engines took effect2

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. However, since 2015, the nation's average ground-level ozone—the main component of smog—has increased by 4%3

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. If wildfire smoke continues to increase at the current rate, smog levels could return to 2003 levels within 20 years, according to lead author Weizhi Deng, an atmospheric scientist at the University of Iowa2

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The research team analyzed wildfires' contribution to surface ozone levels from 2003 to 2024 across the United States, finding that gases in wildfire smoke have forced a shift from declining ozone levels prior to 2015 to increasing levels afterward1

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. "For the last 20 years, by regulations, we keep decreasing the emissions for human-caused smog-inducing chemicals," said study co-author Meng Zhou, a University of Iowa wildfire researcher. "However, because of wildfires, that is actually from natural hazards, all those kinds of effort were wiped out"2

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Artificial Intelligence Reveals Hidden Ozone Pollution Patterns

The study broke new ground by using artificial intelligence to estimate national smog levels with unprecedented detail. Traditional EPA monitors cover only 2% of the nation, mostly in urban areas, leaving significant gaps in air quality data3

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. Researchers combined observations from over 1,000 EPA monitoring stations with satellite-derived information about air pollution, human activity, weather data, and air quality model simulations1

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. They then used artificial intelligence to create a nationwide dataset showing ozone levels at a resolution slightly higher than half a mile (1 kilometer)2

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This AI-powered approach allowed researchers to estimate daily surface ozone levels everywhere in the contiguous United States over the past 22 years1

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. University of Delaware environment professor Cristina Archer, who wasn't part of the study, praised the method as solid because it starts with "massive and reliable datasets," then uses computer models to fill in gaps and create an "exceptional" high-resolution picture2

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. The results revealed that surface ozone levels, which had been falling by about 0.65 parts per billion per year from 2003-2015, have since increased by about 0.13 parts per billion per year1

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Rising Death Toll from Wildfire-Driven Ozone Pollution

The health consequences of reversing progress on cleaner air are severe and measurable. The study estimated an increase of 318 American premature deaths per year since 2013 due to ozone pollution from wildfires2

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. Researchers calculated these figures using previously established epidemiology studies that compared death rates in clean and dirty air3

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. The team of atmospheric scientists and wildfire researchers found that the number of ozone-related premature deaths due to wildfires has been increasing by about 300 deaths per year since 20151

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While fires don't produce ozone directly, they release precursor chemicals that become smog when they interact with sunlight2

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. "Higher daily ozone concentrations can increase asthma attacks, hospital admissions, and mortality," said University of Washington public health and climate scientist Kristie Ebi. Though not quite as deadly as particle pollution, she noted it is "still a very important pollutant, which is why it's regulated"3

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. A 2023 study by many of the same team members found that wildfire smoke increased particle pollution deaths by about 670 per year2

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The Impact of Climate Change on Air Quality Extends Beyond Fire Zones

Wildfire smoke and gas pollutants can travel thousands of miles, affecting communities far from the fires themselves1

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. The 2023 Canadian wildfires offered a vivid example of this widespread impact. During the heavy wildfire smoke seasons of 2022, 2023, and 2024, much of the fires occurred in Canada, but smoke traveled south into the United States3

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. In 2023, 43 million Americans were exposed to smog levels that exceeded the current EPA safety standard, with the impact reaching as far as Georgia and New York1

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. The amount of land burned in 2023 in Canada was not only a record but two times higher than the old record, said atmospheric scientist Brendan Rogers of the Woodwell Climate Research Center2

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The biggest increases in ozone levels occurred in the Northern Rockies, near many of the fires, and in the Midwest, where smoke traveled next3

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. The average amount of U.S. land that wildfires burn each year is now 9% higher than it was from 2003 to 2014, according to the National Interagency Fire Center2

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. As the Earth and its atmosphere warm due to climate change, wildfire seasons are becoming longer and more severe across many parts of North America, with projections suggesting this trend will continue1

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Public Health Efforts Face Mounting Challenges

Protecting public health in this new reality requires both immediate and long-term strategies. In the short term, people can reduce their exposure to ozone pollution by checking air quality forecasts and limiting outdoor activities when wildfires are sending smoke into the air1

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. Megafire Action policy director Teresa Feo emphasized that "experts have long called for expanding the air pollution monitoring network to improve research on wildfire smoke exposure and provide the data needed to better protect public health"3

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Longer-term public health efforts must address the root causes. This includes improving wildfire management by reducing brush and other dry undergrowth that can fuel fires, and scaling back the causes of rising global temperatures, such as burning fossil fuels1

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. As temperatures rise, the ground loses moisture, creating conditions for more extreme fires. However, concerns exist about current regulatory approaches. Dr. Lynn Goldman, former dean of the George Washington University School of Public Health and a former EPA assistant administrator, stated that current EPA safety standards aren't stringent enough3

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. In 2023, the Biden administration delayed plans to tighten those standards, and the Trump administration subsequently changed regulations that consider deaths and health impacts in smog and soot rules2

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. Strengthening air quality forecasting systems to provide accurate early warnings remains essential so people can take necessary precautions1

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