Print article BILLINGS, Mont. — Wildfire smoke accounted for up to half of all health-damaging small particle air pollution in the western U.S. in recent years as warming temperatures fueled more destructive blazes, according to a study released Monday. Even as pollution emissions declined from other sources including vehicle exhaust and power plants, the amount from fires increased sharply, said researchers at Stanford University and the University of California, San Diego. The findings underscore the growing public health threat posed by climate change as it contributes to catastrophic wildfires such as those that charred huge areas of California and the Pacific Northwest in 2020. Nationwide, wildfires were the source of up to 25% of small particle pollution in some years, the researchers said.