Wildfires are changing the air we breathe—here’s what that means for your health

As wildfires grow larger and more frequent across the West, researchers from Colorado, Utah, and California are digging into how smoke affects the air—and our health. 

In a new study published in the journal Atmospheric Environment, the team shows that large wildfires, like those we’ve seen in Colorado, Oregon, and California in recent years, produce large amounts of ozone into the atmosphere. This not only impacts our lungs and other health concerns but also contributes to the warming of the planet. 

CU Denver mathematics professor emeritus Jan Mandel was part of the research team, which included faculty from the University of Utah (UT) and San Jose State University. The study was led by Derek Mallia, a research assistant professor of Atmospheric Sciences at UT, who has long collaborated with Mandel on wildfire modeling. 

The team focused on large wildfires in 2020 that affected much of the Western United States. From Aug. 15-26, 2020, wildfires burned more than 1 million acres across seven northern California counties, causing $12 billion in damage. Dozens of fires raged elsewhere, including Utah’s 90,000-acre East Fork fire and Oregon’s Lionshead and Beachie Creek fires that burned a combined 400,000 acres. During that same time, multiple air quality and pollutant alerts were issued in Colorado as residents dealt with smoke-filled skies.  

Mandel developed most of the computer code used to model the wildfire chemical emissions that ended up in the atmosphere. He worked alongside Mallia and Adam Kochanski, associate professor at San Jose State University, both longtime collaborators. 

“Wildfires do not emit ozone directly,” Mandel said. “Wildfire smoke contains chemical compounds that react with sunlight to produce ozone, often far from the fire itself. Modeling this requires sophisticated atmospheric chemistry and weather prediction software, which we integrated with our wildfire model.” 

The research paper concludes that, on average, the presence of wildfire smoke increases ozone concentrations by 21 parts per billion (ppb). That is on top of already high ozone levels in the West, pushing concentrations beyond the 70-ppb health standard set by the U.S. Environmental Protection Agency. 

Ozone is a health hazard. The Colorado Department of Public Health & Environment states that symptoms can range from coughing to lung and cardiovascular disease and, in some cases, premature death.  

Mandel’s area of expertise includes applied and computational mathematics, high-performance computing, data assimilation, and wildfire modeling. He has multiple mathematics degrees from Charles University in Prague including in computer science, mathematical models in economics, and numerical mathematics. Before joining CU Denver in 1986, Mandel was a senior scientist at Charles University. He has almost 200 published articles and has served on several National Science Foundation advisory panels. He also has provided consulting services to industry, including for the design of the Swedish Grippen jet fighter, and developed a computational method used in Japan in the analysis of Fukushima nuclear reactors on the then fastest supercomputer in the world. In 2025, Mandel was named  among the top 2% of highly cited scientists in the world, according to Stanford University and Elsevier.  In 2021, he was rated by research.com among the top 1000 mathematics scientists globally and top 2,000 in Technology and Engineering. He retired from CU Denver in 2024 but continues at the university as professor emeritus working on NASA-related research. He also serves as a high-performance computing system administrator. 

Other co-authors of the study include undergraduate student Cambria White and Research Scientist Angel Farguell, who was previously a postdoc at CU Denver, both from San Jose State University’s Wildfire Interdisciplinary Research Center. The Utah Division of Air Quality, NASA’s  FireSense Project, and the University of Utah’s Wilkes Center for Climate Science & Policy provided funding for the research.