WASHINGTON (AP) – For more than a decade, the United States has dramatically reduced smog levels in the country, but since 2015 the amount of smoke has been increasing. wildfire A new study finds that the purifying trend is reversing, making the air dirtier and more harmful.
scientists say climate change worthy Many, but not all, of the responsibilities.
National smog levels decreased by 11% from 2003 to 2015 As strict federal regulations For power plants, automobiles, etc. diesel engine But since then, average ground-level ozone (smog) across the country has increased by 4% as wildfires have spread. This means that if smoke increases at its current rate, smog will return to 2003 levels within 20 years, said study lead author Weiji Deng, an atmospheric scientist at the University of Iowa.
Thursday’s study scientific journal They also estimated increased deaths from ozone lung challenge using previously established epidemiological studies that compared mortality rates in clean and dirty air. They calculated that since 2013, there has been an increase of 318 American deaths per year.
“Over the past 20 years, regulations have continued to reduce human-induced emissions of smog-inducing chemicals,” said study co-author Meng Zhou, a wildfire researcher at the University of Iowa. “But in reality, all those efforts were undone by natural disasters such as wildfires.”
Smog monitor coverage is limited
Myra Long looks from inside her home as the Sandy Fire approaches in Simi Valley, Calif., May 19, 2026. (AP Photo/Caroline Breman, File)
Myra Long looks from inside her home as the Sandy Fire approaches in Simi Valley, Calif., May 19, 2026. (AP Photo/Caroline Breman, File)
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This study was novel in that it estimated smog levels across the country, making up for the limited number of U.S. Environmental Protection Agency smog monitors. These cover only 2% of the country and are mostly located in urban areas. So Deng and his colleagues used these observations, as well as satellite, pollution, and weather data and models, and used artificial intelligence to create a national ozone level data set that shows smog counts at slightly higher resolution than half a mile (1 kilometer).
EPA numbers show: National ozone levels since 2015 has fluctuated around the same mark, up and down a few percentage points, but Deng Xiaoping said, “When we consider every location in the United States, we find that ozone has actually increased since 2015.”
Christina Archer, an environmental professor at the University of Delaware who was not involved in the study, said the artificial intelligence-powered approach is robust because it starts with “large, reliable data sets” and then uses computer models to intelligently fill in the gaps and create “exceptional” high-resolution images.
“For years, experts have called for expanded air pollution monitoring networks to improve research on exposure to wildfire smoke and provide the data needed to better protect public health,” said Teresa Feo, director of research and senior policy advisor at MegaFire Action.
For decades, the United States has tracked six traditional air pollutants, including small particles such as smog and soot. This new study looked only at ozone; 2023 survey Many of the same teams investigated small particle contamination. They found that the downward trend in soot levels was similarly reversed. A 2023 study found that wildfire smoke caused about 670 more deaths per year due to particle pollution.
How fires cause health problems
Firefighters work as the Sandy Fire approaches in Simi Valley, Calif., May 19, 2026 (AP Photo/Caroline Breman, File)
Firefighters work as the Sandy Fire approaches in Simi Valley, Calif., May 19, 2026 (AP Photo/Caroline Breman, File)
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Scientists say fires themselves do not produce ozone, but when they react with sunlight they release precursor chemicals that become smog.
“Higher daily ozone concentrations can increase asthma attacks, hospitalizations, and mortality,” said Christy Ebi, a public health and climate scientist at the University of Washington. While not as deadly as smaller particles, “they are still very important contaminants and that’s why they’re regulated,” she said.
During the heavy wildfire smoke seasons of 2022, 2023 and 2024, many of the fires started in Canada, but the smoke reached the south. A study found that 43 million people in the United States are exposed to levels of smog that exceed current EPA safety standards.
And those standards aren’t rigorous enough, says Dr. Lynn Goldman, former dean of George Washington University’s School of Public Health and former EPA deputy administrator. Biden administration will be inaugurated in 2023 delay plans to strengthen those standards; and the trump administration Regulatory changes that take into account mortality and health impacts With smog and soot rules.
Deng said ozone levels rose the most in the northern Rocky Mountains, near many of the fires, and then in the Midwest, where the smoke moved.
More fire means more smoke
A man runs in front of the sun as it rises over the Lower Manhattan skyline in Jersey City, N.J., June 8, 2023. (AP Photo/Seth Wenig, File)
A man runs in front of the sun as it rises over the Lower Manhattan skyline in Jersey City, N.J., June 8, 2023. (AP Photo/Seth Wenig, File)
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The average amount of U.S. land burned each year by wildfires is now 9% higher than from 2003 to 2014. According to the National Interagency Fire Center. But scientists say Canada’s wildfires will be especially bad starting in 2022. They pointed to 2023, when the sky was orange and people in the east were wearing masks because of smoke in Canada.
Atmospheric scientist Brendan Rodgers of the Woodwell Climate Research Center says the amount of land burned in Canada in 2023 is not only a record, it’s double the previous record. Smoke from the Canadian wildfires that year killed 82,100 people worldwide due to particle pollution, and 33,000 in the United States. Calculated in 2025 survey.
Climate change from the burning of coal, oil and gas has increased the intensity of Canada’s 2023 fire season by at least 50 per cent and doubled the likelihood of the drier and hotter weather conditions necessary for fires. This was discovered in a study in 2023.
“Anthropogenic climate change is an important factor because it increases hotter, drier fire weather conditions in many regions,” said Rix Jin, an atmospheric scientist at Rutgers University who was not involved in the study. “But wildfire emissions also depend on fuel, land management, ignition, fire suppression, and year-to-year weather conditions.”
Former Environmental Protection Agency Administrator Gina McCarthy, who served in the Obama administration, said it’s disheartening to see smog improvements being undermined.
Wildfires cause death and destruction, but the greatest danger may come from the smoke and extreme heat, which increases ozone, which is harmful to people’s health.
“So the big question is when will we stop this administration’s nonsense of burning more ‘beautiful’ fossil fuels?” she said.
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