A new University of Iowa study in the journal Science shows that wildfire smoke is undoing years of clean air gains across the United States. Between 2015 and 2024, surface ozone levels increased by 0.13 parts per billion each year, reversing progress that took more than a decade. The researchers found that without wildfire smoke, ozone would have kept falling. In 2023 alone, Canadian wildfire smoke pushed ozone above federal limits for 148 million people, leading to nearly 8,000 premature deaths. The problem is that current U.S. air quality rules were built for local pollution sources like cars and factories. Wildfire smoke travels hundreds or thousands of miles, making it hard for states to manage. The EPA allows exceptional event claims for pollution spikes beyond local control, but these events are no longer rare. The study tracked ozone using satellite data and ground monitors across the continental U.S., linking smoke to rising health risks and showing that the system needs to adapt to a warming world where wildfires are more frequent and severe.
