Researchers at the University of California Los Angeles and UC Davis reported on June 3 that a carcinogen with potential health impacts was found in neighborhoods following the 2025 Los Angeles County wildfires. The findings indicate that airborne hexavalent chromium, also known as chromium-6, may have spread to communities located six to nine miles downwind from fire cleanup zones.
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. Although still subject to final revisions, the study was released early to inform other researchers and the public. Researchers found that two months after the fires, airborne chromium levels were below workplace exposure limits set by the National Institute for Occupational Safety and Health, but exceeded screening levels established by the U.S. Environmental Protection Agency for indoor air.
Models used in the research suggest that chromium-containing nanoparticles could have traveled beyond directly affected areas into parts of southern San Fernando Valley, Beverly Hills, and West Hollywood. Michael Jerrett, professor in UCLA’s Department of Environmental Health Sciences and Jonathan Fielding Chair in Climate Change and Public Health, said, “Monitoring near wildfire cleanup zones is warranted to ensure that concentrations decay to background levels over time.” Jerrett also said, “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 in western Los Angeles and Altadena-Pasadena near the San Gabriel Mountains. According to county reports cited by researchers, at least 31 lives were lost and more than 18,000 structures were damaged or destroyed during these events.
The University of California Los Angeles has been associated with Nobel laureates and MacArthur Fellows; it operates within a 419-acre campus supporting academic excellence across diverse fields through its programs within the University of California system, according to the official website.
