Nineteen months after the wildfires erupted in Pacific Palisades and Altadena, USC researchers on Tuesday announced findings showing elevated lead levels in some neighborhoods while concluding that most fire-related chemicals detected in coastal waters returned to typical levels within months.
The findings are part of USC’s Contaminant Level Evaluation and Analysis for Neighborhoods project, known as CLEAN, which analyzed more than 6,000 soil samples collected from more than 3,000 households and more than 900 seawater samples.
“Communities deserve clear, science-based information about their environment after the LA fires,” Dr. Erika Garcia, a USC Keck associate professor and environmental epidemiologist who advises the CLEAN project, said in a statement. “With clear data about what is in their soil, LA 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.”
Researchers said the fires released lead into the environment, but preexisting contamination from sources such as lead-based paint at older homes makes it difficult to distinguish fire-related contamination from existing pollution.
The report also found no evidence of countywide post-fire contamination from other metals that generated concern after the fires, including arsenic, mercury and hexavalent chromium.
According to the study, lead concentrations varied widely across individual properties, with one soil sample on average containing about twice as much lead as another collected just a few feet away. Researchers said the findings underscore the importance of testing individual properties.
“Every property is different,” said Josh West, a USC Dornsife professor of Earth 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.”
The CLEAN Waters team also monitored Southern California beaches and coastal waters for 18 months, finding that nutrients, metals and hundreds of fire-related compounds increased in the weeks after the fires before returning to more typical levels within several months.
“The fires left a clear signal in the ocean, but it wasn’t a permanent one,” USC Dornsife Biological Sciences Assistant Professor Noelle Held said. “We were able to track how fire-related chemicals moved through coastal waters and watch many of them decline over time.”
USC said the research builds on earlier studies of heavy metals in beach sand and seawater and provides a broader picture of how wildfire debris affected coastal ecosystems.
Researchers also released a home and yard guide to help residents reduce potential exposure to contaminants and said the CLEAN project has expanded its sampling efforts to examine lead concerns following the Boyle Heights warehouse fire. The guide can be found at https://www.consortium-science.com/.