The Conversation

Wildfires are reversing America’s progress on ozone pollution, the main ingredient in smog

Jun 9, 2026 • By Magazine Editor

For decades, the United States made steady progress in reducing surface ozone pollution, the main ingredient in smog. But that progress – achieved as vehicles, industries and power sources became cleaner – is increasingly being overshadowed by a different and growing source of ozone pollution: wildfires. We found that the gases in wildfire smoke have reversed the national ozone trend, forcing a shift from declining ozone levels prior to 2015 to increasing ozone levels after 2015.