Wildfires are undoing years of cleaner air in the U. S.

For over a decade, the U. S. had been making steady progress in reducing ground-level ozone—a harmful pollutant that damages lungs and triggers breathing problems. Between 2003 and 2015, average ozone levels dropped by about 0. 65 parts per billion each year. But around 2015, something changed. Wildfires began spreading faster and burning hotter, filling the air with smoke that reacts to create even more ozone. Now, instead of dropping, ozone levels are creeping back up by roughly 0. 13 parts per billion annually.The impact isn’t just numbers on a chart. Researchers found that smoke from wildfires has wiped out nearly four years of clean-air improvements. Worse, it’s making people sick. Premature deaths linked to ozone from fires have jumped by about 318 every year since 2013, with deaths after that year 46% higher than before. In just three recent years, wildfire smoke exposed 43 million Americans to air quality that fails health safety standards. That’s like adding a whole new city the size of Los Angeles to the list of places where breathing the air could be dangerous. What makes this trend especially troubling is that it’s tied to climate change. Hotter temperatures and drier conditions are feeding bigger, more frequent fires. Even as the country works to cut pollution from cars and factories, the fires are undoing some of that hard work. If wildfires keep growing, meeting stricter air quality goals could become much harder—maybe even impossible in some regions.