More than a year after the historic Pacific Palisades and Eaton fires, residents still face urgent environmental questions: Is my soil contaminated? Are the beaches safe? What should I do if contamination is found?
After more than a year of research, USC scientists 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. The reports deliver a clear look at how the fires affected environmental contamination and where other sources of contamination remain a 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.”
The findings from this CLEAN report suggest that the fires did release lead into the environment, but also that 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.
Further, the CLEAN team 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.” While the soil team focused on neighborhoods, CLEAN Waters 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,” Held said. “We were able to track how fire-related chemicals moved through coastal waters and watched 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.”
To help residents manage exposure regardless of its source, the recently formed CONSORTIUM (a collaborative effort among USC CLEAN, partner universities and community groups) has launched a practical home and yard guidance guide available on the CONSORTIUM website .
CLEAN continues to adapt dynamically to new threats, recently expanding its sampling model to address lead concerns following the June warehouse fire in Boyle Heights.
Residents can visit the CLEAN website to sign up for updates and receive new research findings as they become available.