A study led by Minghao Qiu of Stony Brook University, published on May 8 in Science Advances, finds that wildfire smoke significantly raises ground-level ozone levels and contributes to thousands of excess deaths annually in the United States.
The findings highlight a health risk from wildfires that is not always visible. While most research has focused on particulate matter from fire smoke, this study shows that ozone—an invisible gas—is also a major concern. Ozone exposure is linked to respiratory and cardiovascular problems, reduced cognitive performance, and increased mortality.
“As we move further into spring and then summer, wildfires will most likely increase in the United States and all of North America, and scientists should be thinking about the effects of increased ozone from fires in addition particulates emitted into the air,” said Qiu, who is an assistant professor at Stony Brook University’s School of Marine and Atmospheric Sciences. The research team used nearly two decades of surface ozone measurements (2006 to 2023), meteorological data, satellite data, and machine learning models to analyze changes in surface ozone concentration during fire episodes across the continental U.S.
The researchers found that wildfire smoke can boost daily ground-level ozone by as much as 16 percent in some regions such as the eastern part of the country and Midwest. This increase is significant enough to cause more illnesses and deaths attributed to fire-related air pollution. The team estimates that more than 2,000 excess deaths per year are linked specifically to wildfire-related increases in ozone levels among people ages 65 and over.
Qiu said two key points are important: “The true health effects and death toll from wildfire smoke are likely higher than previously thought, given that prior research has not factored in ozone exposure,” he said. He also warned that even days with good visibility after wildfires may still have harmful levels of unseen ozone because particulate matter pollution does not always overlap with high-ozone conditions.
The study’s results suggest challenges for ongoing efforts to improve air quality nationwide. The researchers note their findings show increases in wildfire-driven ozone partially cancel out long-term declines achieved through other clean-air measures. Funding for this work came from several sources at Stony Brook University as well as a grant from NOAA’s Climate Program Office’s Atmospheric Chemistry program.
Stony Brook University News contributed media coverage supporting journalists by providing access to university experts on science topics such as this research according to its official website.
