Eaton fire smoke carried lead levels 80 times above background, study finds

During the peak of the 2025 Los Angeles Eaton firestorm, airborne lead concentrations exceeded 80 times normal background levels, according to new research published in Science Advances. The study also found heightened levels of arsenic, halogens, and heavy metals in the urban smoke plume, which the researchers determined was far more hazardous than a wildland fire plume from the previous year.

The fire, which originated in Eaton Canyon, destroyed more than 9,000 structures and coated the Los Angeles basin with a plume of chemicals released from burning electronics, building materials, and vehicles. Haroula Baliaka and colleagues characterized the plume’s changing composition by analyzing airborne trace elements and tracking hourly potassium-lead ratios throughout the event.

To assess how urban fires differ from conventional wildfires, the team compared the Eaton plume with the content of a nearby 2024 wildland-exclusive fire plume. The urban plume showed a more than 50-fold higher concentration of lead, 7-fold higher levels of halogens in the form of chlorine and bromine, 4-fold higher zinc, and 3-fold higher copper and arsenic. The analyses suggest that at peak burn, lead concentrations exceeded the typical background level for around 7 million residents over 24 hours.

The researchers emphasize that the health consequences of this acute exposure remain unknown. “Millions of residents faced an acute toxic metal burden with unknown health consequences,” Baliaka and colleagues write. “Understanding and ultimately mitigating these health risks must become a priority as such [urban] events grow more frequent and severe.” As human development expands into traditional wildlands, urban wildfires are becoming increasingly common, and their smoke contains far more chemical pollutants than smoke from forest and grassland fires.

Subject of Research: Toxic metal composition of the 2025 Los Angeles Eaton urban fire smoke plume

Article Title: The Los Angeles Eaton fire caused a surge of airborne lead, arsenic, and halogens

Article References: The Los Angeles Eaton fire caused a surge of airborne lead, arsenic, and halogens. Original publication (Bibliographic details unavailable.)

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Keywords: Eaton fire, Los Angeles, urban wildfire, airborne lead, arsenic, halogens, heavy metals, smoke plume, air quality, Science Advances, wildfire pollution, Angeles