A new study led by researchers at the University of Southern California Dornsife College of Letters, Arts and Sciences reports that the 2025 Eaton fire produced a surge in carbon monoxide and particulate matter that far exceeded Los Angeles County’s average daily human-caused emissions. The findings were released on Mar. 12 and highlight how a single urban wildfire can quickly escalate into a regional air-quality crisis.
The research underscores the public health risks posed by wildfires in urban areas, as smoke from the Eaton fire spread across Los Angeles, raising concerns about respiratory and psychological effects. Keck School of Medicine of USC researchers are now studying these impacts.
Researchers estimated that the Eaton fire generated carbon monoxide at rates more than 20 times higher than typical daily emissions from human activity in L.A. County. “People could see the smoke, but they couldn’t see the scale of the pollution it was carrying,” said William Berelson, professor of Earth sciences at USC Dornsife and co-author of the study. “This one fire was producing carbon monoxide on a scale that exceeded the entire county’s usual daily emissions from human activity.”
The study found that burning homes and other structures contributed more to carbon emissions than vegetation did, which helped explain why this particular fire had such a large impact on regional air quality. Researchers used satellite imagery, computer modeling, and ground-based air measurements—including data from Carbon Census network sensors deployed around Los Angeles—to track what burned and how smoke moved across the region.
According to estimates, about 153 million kilograms (337 million pounds) of carbon were released during the Eaton fire. Smoke reached downtown Los Angeles within hours before moving west toward coastal areas. At some monitoring sites, levels of fine-particle pollution known as PM2.5 surpassed federal health standards for up to three days.
The January 2025 fires affected different parts of Los Angeles in various ways; however, while early emissions from another blaze—the Palisades fire—were carried offshore by winds, smoke from the Eaton fire moved directly into central and western neighborhoods.
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Study authors include Pietro Vannucci and Wenye Wang of USC Dornsife as well as Jooil Kim and Timothy Lueker from Scripps Institution of Oceanography at UC San Diego. The research received support through a President’s Sustainability Award and a USC Dornsife Public Exchange Grant.
