Study Suggests Carcinogenic Chromium Particles Spread Miles Beyond LA Wildfire Cleanup Zones

A file photo of Debris removal operation in Altadena (Photo – Kevin Nha, US Army Corps of Engineers)

A peer-reviewed study published in June by researchers at UCLA and UC Davis found airborne carcinogenic chromium nanoparticles in neighborhoods surrounding cleanup zones after the 2025 Los Angeles County wildfires. Modeling suggests the particles may have traveled as far as 6 to 9 miles downwind.

By News Desk

The research, titled Airborne hexavalent chromium nanoparticles detected around cleanup zones for the 2025 Los Angeles wildfires, was published in Nature Communications Earth & Environment. The researchers said the study was released early to make its findings available to scientists and the public while the journal completes final production revisions.

Two months after the fires, the airborne chromium was predominantly in its hexavalent form, a carcinogenic oxidation state, the researchers reported. Measured concentrations were below the National Institute for Occupational Safety and Health workplace exposure limit but above the U.S. Environmental Protection Agency’s screening levels for indoor air.

Using models that estimate how contaminants travel in the wind, the researchers concluded that chromium-containing nanoparticles may have spread 6 to 9 miles from cleanup zones into surrounding communities. In the case of the Palisades Fire, the study said those areas could include parts of the southern San Fernando Valley to the north, as well as Beverly Hills and West Hollywood to the east.

“Monitoring near wildfire cleanup zones is warranted to ensure that concentrations decay to background levels over time,” said study co-author Michael Jerrett, professor in the Department of Environmental Health Sciences at the UCLA Fielding School of Public Health. “Residents living adjacent to wildfire cleanup zones should take steps to reduce their exposure by using indoor air filters and limiting outdoor exercise in the fire zones until conditions return to safe levels.”

The study follows the January 2025 Los Angeles County wildfires in the Pacific Palisades-Malibu area and the Altadena-Pasadena-Sierra Madre communities. According to Los Angeles County, the fires claimed at least 31 lives and damaged or destroyed more than 18,000 structures.

The researchers said continued monitoring around wildfire cleanup areas is warranted to determine whether airborne chromium concentrations return to background levels over time.