During the devastating 2025 Los Angeles Eaton firestorm’s peak, airborne lead concentrations exceeded 80 times the normal background levels, new research finds. The work establishes that this urban smoke plume – which also included heightened levels of arsenic, halogens, and heavy metals – was far more hazardous than a wildland plume the year prior. “Millions of residents faced an acute toxic metal burden with unknown health consequences,” Haroula 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 humans expand into traditional wildlands, urban wildfires are becoming increasingly common. These fires produce smoke that contains far more chemical pollutants than forest and grassland fires. The 2025 Los Angeles firestorm, originating in Eaton Canyon, obliterated more than 9,000 structures. It coated the Los Angeles basin with a plume of chemicals from burning electronics, building materials, and vehicles. Now, Baliaka et al. have characterized the plume’s changing composition during the fire. They analyzed its composition of airborne trace elements, tracking hourly potassium-lead ratios. Compared with the content of a nearby 2024 wildland-exclusive fire plume, the Los Angeles Eaton plume had a more than 50-fold higher concentration for lead, 7-fold higher for halogens (chlorine and bromine), 4-fold for zinc, and 3-fold for copper and arsenic. Baliaka et al.’s analyses suggest that, at peak burn, lead concentrations exceeded 80 times the typical background level for around 7 million residents over 24 hours.
Science Advances
Fire at the boundary: Airborne toxic metals from the 2025 Los Angeles urban firestorm
28-Oct-2026