Wildfire smoke increases ground‑level ozone and adds deaths in the US ^{CEFR B2}

The study, led by Minghao Qiu of Stony Brook University with lead author Yangmingkai Li, appears in Science Advances. The researchers combined surface ozone measurements from 2006 to 2023 with meteorological and satellite observations and used machine learning models to estimate how ozone changed during fire episodes. They relied on the satellite‑based NOAA Hazard Mapping System (HMS) smoke plume product to define smoke days and compared ozone on smoke and non‑smoke days while controlling for ambient temperature and ultraviolet radiation.

Results show that wildfire smoke can raise daily ground‑level ozone by as much as 16% in some regions, notably parts of the eastern United States and the Midwest. Translating these changes into health impacts using exposure‑response relationships, the team estimates that smoke‑driven ozone increases excess US deaths per year by more than 2,000. Because some exposure‑response functions were derived from studies of older adults, the researchers reported mortality estimates for ages 65 and over for consistency.

The paper highlights important implications. First, prior work that focused mainly on particulate matter has likely underestimated the full health burden of wildfire smoke by neglecting ozone exposure. Second, days that appear clear after fires can still carry an ozone risk because particulate pollution and ozone do not often overlap and ozone is invisible. The added ozone from wildfires can slow progress on improving air quality and partly offset long‑term national declines in ozone and related mortality.

The research received partial support from the Minghua Zhang faculty career catalyst award at SoMAS and Stony Brook University, and from the NOAA Climate Program Office’s Atmospheric Chemistry, Carbon Cycle, and Climate Program.

• Data period: 2006 to 2023
• Maximum ozone increase observed: 16%
• Estimated excess deaths per year: more than 2,000 (ages 65 and over)