A chemical analysis of residential soils and ash around California homes burned by the Eaton and Palisades wildfires in early 2025 revealed wide variation in contamination by potentially harmful elements, including lead, according to a study published in Environmental Science and Technology Letters on May 12. The researchers made their findings available to the Los Angeles Public Health Department over the course of the study.

The January wildfires burned across two Los Angeles communities, Altadena and Pacific Palisades, killing 31 people and destroying more than 16,000 structures, most of which were homes.

“Homes often contain metals in structural materials and household products, and fires release metals in smoke but also concentrate metals in structural ash that can potentially contaminate residential soils,” says author Daniel Richter, the Theodore S. Coile Distinguished Professor of Soils and Forest Ecology at Duke University’s Nicholas School of the Environment, who oversaw the study. 

While the fires were still burning, Richter spoke with a Los Angeles-based colleague who put him in touch with Robin Jones, founder of a small garden design business in LA called Honey Girl Grows.

Jones helped organize and train a local team of volunteer homeowners to collect samples of soil and ash from more than 30 burned residences. By March of that year, the team had gathered 300 samples and shipped them to Richter’s laboratory for analysis. 

Details in the Data

At Duke, first author Anselme Dossou, a Ph.D. student in Richter’s lab, led a team of student volunteers in preparing and analyzing the soil and ash samples for metal contaminants. They found highly variable levels of lead and arsenic across both sample types. 

Lead levels were highest in the structural ash from a fraction of homes built before the 1970s, likely from lead-based paints used at the time, according to the team.

In June and July, after a cleanup effort conducted by the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (USACE), the team gathered more than 100 additional samples from 17 residences. Those sites were located within a meter of the original sampling sites collected before cleanup.

“Together the agencies removed nearly 2.4 million tons of burned and hazardous materials — a massive cleanup that targeted house foundations and structural ash where six inches of ash and soil were scraped for removal,” Richter says.

After analyzing the additional samples, the team found that the cleanup greatly reduced concentrations of lead and arsenic in burned areas that had been scraped, especially at sites that had shown the highest concentrations of those contaminants.

“These data are especially important because they are some of the only comparisons of pre- and post-cleanup, as the USACE did no testing following these fires,” Richter says.

Additional Insights

The study highlights an area of disagreement regarding cleanup effectiveness, according to Richter. California is currently the only state that has its own level for lead in residential soil. That lead level is less than half the federal standard set by the EPA.

“The two lead concentrations needlessly confuse the public, and they critically need a technical review,” Richter says.

The findings also underscore a commonality among many urban areas: The soils in communities burned by the Eaton and Palisades fires are reminiscent of soils underlying cities and towns across the nation that contain leftover metal contaminants from historical use, according to the authors.

“To quote my Ph.D. student Anselme Dossou, ‘soils have long memories,’” Richter says.

Learn more about the study results in this video discussion presented by the study authors.

Citation: Dossou SA, Kelly L, Lu PL, Jones R, O’Donnell O, Walsh JS, Richter DD. 2026. “Urban Conflagrations: Structural Ash and Soil Metal(Loid) Contamination From California’s Eaton and Palisades Fires,” published in Environmental Science and Technology Letters.