A chemical analysis of residential soils and ash near California homes destroyed by the Eaton and Palisades wildfires in early 2025 found wide differences in contamination by potentially harmful elements such as lead, according to research published in Environmental Science and Technology Letters. The results were shared with the Los Angeles Public Health Department during the study.
The January fires affected two Los Angeles areas, Altadena and Pacific Palisades, resulting in 31 deaths and the loss of more than 16,000 structures, mostly homes.
Homes frequently include metals in building materials and consumer goods, and fires can release these metals in smoke while concentrating them in ash that may affect nearby soils, noted Daniel Richter of Duke University, who led the project.
While the fires continued, Richter connected with local resident Robin Jones, who organized and trained volunteer homeowners to collect more than 300 soil and ash samples from over 30 burned properties. The samples reached Richter’s lab by March.
At Duke, doctoral student Anselme Dossou directed analysis of the samples, revealing highly variable lead and arsenic concentrations in both ash and soil. The highest lead amounts appeared in ash from some pre-1970s homes, likely due to older lead-based paints.
Following a major cleanup by federal agencies that removed nearly 2.4 million tons of debris, additional samples taken from 17 sites showed sharp reductions in lead and arsenic where scraping had occurred.
The data provide rare before-and-after comparisons, as no post-cleanup testing was conducted by the agencies involved. The study also notes differing standards for lead in soil between California and federal guidelines, calling for further technical review. The findings reflect broader patterns of historical metal residues in urban soils nationwide.
