More than a year after the Palisades and Eaton fires, many residents are still asking: Is my yard contaminated? What about the beach? And what should I do if there is contamination?
USC scientists have been investigating these questions since the fires were put out - and are providing answers. This week, USC's Contaminant Level Evaluation and Analysis for Neighborhoods (CLEAN) project released new findings drawn from more than 6,000 soil samples collected across Los Angeles County, and more than 900 seawater samples collected along the Southern California coast.
Together, the reports provide one of the most comprehensive pictures yet of how the fires affected environmental contamination - and where other potential sources of contamination remain of great concern.
"Communities deserve clear, science-based information about their environment after the L.A. fires," said Erika Garcia, associate professor at the Keck School of Medicine of USC and epidemiological advisor to CLEAN. "With clear data about what is in their soil, L.A. residents can make more informed decisions about engaging in possible risk reduction strategies, or perhaps their minds will be put at ease knowing that their soil lead is not at a level of high public health concern."
What's in the soil?
CLEAN was launched just two months after the January 2025 fires. And since then, more than 3,000 Los Angeles households have submitted soil samples for CLEAN to test for lead and other contaminants.
The findings from this CLEAN report suggest that the fires did release lead into the environment, but also that across the county, preexisting sources of contamination - such as older homes, which are more likely to have released flakes of old lead-based paint over time - make it difficult to distinguish the impacts of the fires from those other sources of lead. Researchers also found no evidence of countywide post-fire contamination from other metals that generated concern after the fires, including arsenic, mercury and hexavalent chromium.
The CLEAN team also found that lead levels across a property can vary widely - on average, one sample from a property has about twice as much lead as another just a few feet away. That variation can be even more extreme within the burn zones, which is why widespread lead testing is so important.
"Every property is different," said Josh West, professor of earth sciences at the USC Dornsife College of Letters, Arts and Sciences and a principal investigator on the CLEAN project. "Lead levels can vary substantially even within a single yard, so testing your own soil remains the best way to understand potential exposure."
Are Southern California beaches safe?
While the soil team focused on neighborhoods, the CLEAN Waters team tracked fire-related pollutants in Southern California beaches and coastal waters.
Led by USC Dornsife Assistant Professor of Biological Sciences Noelle Held, the CLEAN Waters team has spent the last 18 months examining pollution that could threaten coastal communities and marine plants and animals. Their new findings build on an earlier study of heavy metals in beach sands and seawater, providing a more complete picture of how wildfire debris affected the coast.
Their research found that the fires did leave a measurable chemical fingerprint in coastal waters - but it was largely temporary. Nutrients, metals and hundreds of fire-related compounds increased in the weeks immediately following the fires, before returning to more typical levels within a few months.
"The fires left a clear signal in the ocean, but it wasn't a permanent one," said Held. "We were able to track how fire-related chemicals moved through coastal waters and watch many of them decline over time. This kind of sustained monitoring helps us distinguish the impacts of a single disaster from the pollution our coastal ecosystems face every day."
What can I do if there is contamination?
For many fire survivors, the distinction between new contamination and decades-old sources is less important than knowing how to reduce exposure.
Helping communities answer that question is the next phase of the work.
CONSORTIUM - the Community-Oriented Network for Scientific Observation, Recovery, and Tracking of Impacts from Urban Megafires - has released practical guidance to help residents evaluate and reduce contamination where they live, work, and play. The collaborative initiative brings together USC CLEAN with researchers from other universities and community organizations to support neighborhoods affected by fire.
The guidance is available on the CONSORTIUM website.
Meanwhile, CLEAN continues to expand its research in response to community needs. Following the lengthy Boyle Heights warehouse fire, the team quickly adapted its sampling program to evaluate lead levels in affected neighborhoods, demonstrating the model's flexibility as new environmental concerns emerge.
As communities continue rebuilding, CLEAN researchers will continue testing, monitoring and sharing findings - following both the science and the questions residents continue to ask.
Residents can visit the CLEAN website to sign up for updates and receive new research findings as they become available.
