Fires reverse progress toward ozone air quality standards in the United States
- Weizhi Deng
- Jun Wang
- Meng Zhou
- Xi Chen
- Xiaodong Wu
- Huanxin Zhang
- Jason B. Cohen
- Jing Wei
- Arlindo da Silva
- Guy P. Brasseur
- Claire Granier
- Laurence Rouil
2026-06-04
Recent surges in wildfire emissions have exacerbated surface ozone pollution in the United States. Using deep learning, we developed a gapless daily surface ozone dataset at 1-kilometer resolution for 2003–2024. This dataset revealed a reversal in national policy–relevant ozone trends that had gone undetected by the sparse monitoring network: from −0.65 parts per billion (ppb) per year (2003–2015) to +0.13 ppb per year (2015–2024). The reversal was primarily driven by increasing wildfire emissions, offsetting 3.9 years of mitigation progress. Premature deaths from fire-sourced ozone have increased by 318 deaths per year since 2013, with post-2013 mortality 46% higher than pre-2013 mortality. During 2022–2024, wildfire emissions exposed 43 million people to nonattainment conditions, effectively preventing a 4-ppb tightening of the ozone standard. These results underscore the growing challenges of sustaining air quality progress as wildfires intensify under climate change.