A chemical analysis of residential soils and ash around homes burned by Southern California's Eaton and Palisades wildfires in early 2025 has uncovered significant variation in contamination by potentially harmful elements. The peer-reviewed study, published in Environmental Science and Technology Letters on May 12, focused on properties affected by the twin blazes.
Researchers detected uneven concentrations of lead, arsenic, and other toxic metals across sampled sites, suggesting contamination patterns depend on factors like home age and burn intensity. The findings were shared with the Los Angeles Public Health Department throughout the study period, giving officials an early look at emerging risks.
No single contamination level was uniform across the affected areas. Some samples showed elevated lead concentrations while neighboring properties remained below health benchmarks, highlighting the patchy nature of the hazard. The study did not report specific numeric averages or thresholds.
Returning residents may face variable exposure risks depending on their property's specific contamination profile. The Los Angeles Public Health Department now has data to inform cleanup priorities and public health guidance for neighborhoods rebuilding after the fires.
The study's authors emphasized that soil contamination varied widely, warning against generalizing risks across the entire burn zone. They called for property-by-property assessments rather than blanket safety declarations.