"Wildfire smoke contains chemical compounds that react with sunlight to produce ozone, often far from the fire itself." Mandel developed a computer model to gauge the air quality effects of large western wildfires that ripped across the West in 2020. Hundreds of miles from the wildfires, in Colorado, residents grappled with smoke-filled skies and repeated air quality and pollution alerts. On top of already high ozone levels in the West, that pushes levels over the U.S. Environmental Protection Agency's 70-ppb health standard. "Thus, improving air quality across the western U.S. during the summer remains challenging," the study added.