Researchers from the University of California Los Angeles and UC Davis found carcinogenic hexavalent chromium in neighborhoods near wildfire cleanup zones in Los Angeles County months after the 2025 wildfires, according to a June 3 report. The peer-reviewed study, titled “Airborne hexavalent chromium nanoparticles detected around cleanup zones for the 2025 Los Angeles wildfires,” was published in Nature Communications Earth & Environment and is available for early access as it undergoes final revisions.
The researchers reported that airborne chromium was predominantly in a carcinogenic oxidation state two months following the fires. Measurements were below workplace exposure limits set by the National Institute for Occupational Safety and Health, but exceeded U.S. Environmental Protection Agency screening levels for indoor air. Modeling suggested that chromium-containing nanoparticles could have traveled six to nine miles downwind from cleanup areas, reaching communities such as Beverly Hills, West Hollywood, and parts of the San Fernando Valley.
“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 UCLA Fielding School and Jonathan Fielding Chair in Climate Change and 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 January 2025 blazes affected both Pacific Palisades-Malibu near the Santa Monica Mountains and Altadena-Pasadena near the San Gabriel Mountains. The fires claimed at least 31 lives and damaged or destroyed more than 18,000 structures across Los Angeles County.
The University of California Los Angeles has been associated with Nobel laureates, MacArthur Fellows, diverse perspectives through academic programs, national acclaim for scholarship and athletics, and operates within a 419-acre campus as part of the University of California system, according to its official website.
