Iowa study: US surface ozone up 4% since 2003 as wildfire smoke erases gains
A University of Iowa study published Thursday found US surface ozone rose 4% from 2003 to 2024, erasing about four years of clean-air gains nationally and as much as six years across the Western United States. Smog had fallen 11% between 2003 and 2015 before the trend flipped.
The NASA-funded team mapped ozone in kilometer-by-kilometer grids across the continental United States from 2003 to 2024. Concentrations climbed about 0.13 ppb between 2015 and 2024, with air quality deteriorating across the Midwest and Western states.
The team's simulations point to wildfires as the cause. Stripping fire emissions from the model left ozone declining; adding them back pushed smog higher.
"The total reversal," principal author Weizhi Deng said, "is about four years of progress or as high as six in the Western U.S.". Co-author Meng Zhou said one-third of ozone mitigation efforts implemented before 2015, including factory shutdowns and vehicle emission rules, have been wiped out by wildfires.
Researchers linked fire-sourced ozone to 318 additional premature deaths per year since 2013. The mortality estimate draws on the same gridded dataset behind the air-quality trend.
The Environmental Protection Agency and state regulators now face a precursor problem they cannot fully control. Industrial closures and tighter tailpipe rules keep cutting nitrogen oxide and volatile organic compound emissions, but fire-season chemistry is offsetting those gains across the regions the Iowa team measured.
Source: insideclimatenews.org (opens in a new tab)1 sourcePermalink