Chicago, US,August 30, 2025
A new report reveals that climate-fueled wildfires are reversing decades of clean air progress in the US, posing a significant threat to public health and the environment. The study, conducted by the University of Chicago’s Energy Policy Institute, found that record-breaking wildfire seasons, particularly in Canada, have led to a sharp increase in air pollution across the US. The report highlights that this new wave of pollution is undoing years of hard work to improve air quality and is a direct consequence of a warming climate.
A Step Backwards for Air Quality
The United States and Canada, despite having some of the world’s most stringent air quality regulations, have seen the largest increase in fine particulate pollution (PM2.5) globally. The study found that pollution levels in the US in 2023 rose by 20% compared to 2022, primarily due to smoke from Canada’s worst-ever wildfire season. This rise in pollution has undone roughly 25% of all US air quality improvements since 2000. For the first time in a decade, the most polluted counties in the US were not in California but in Midwestern states like Wisconsin, Illinois, and Indiana, which were downwind of the Canadian fires.
The Health and Climate Connection
Wildfire smoke is a complex mix of pollutants, including fine particulate matter, which can penetrate deep into the lungs and even enter the bloodstream. This can lead to a range of health issues, including heart attacks, strokes, asthma, and other chronic lung diseases. The study found that a given level of PM2.5 from wildfire smoke has worse health outcomes than other forms of pollution, such as from vehicle emissions.
The report also highlights the vicious cycle between climate change and wildfires. A warming climate creates hotter, drier conditions, which lead to more frequent and intense fires. These fires, in turn, release massive amounts of greenhouse gases and other pollutants into the atmosphere, further accelerating climate change. As one of the report’s co-authors, Michael Greenstone, stated, “Air pollution is like the zombie that we thought we had killed, but now it’s back.”
The findings underscore the urgent need for a more comprehensive approach to climate action. While policies aimed at reducing emissions from fossil fuels have been effective, the report shows that the secondary effects of climate change, such as wildfires, are now a major source of pollution.
