Testing for Soil Toxins After the L.A. Fires

Introduction to Soil Toxin Testing

Over three days in late March, four Los Angeles Times environment reporters and an editor fanned out across the Eaton and Palisades burn scars to collect 40 soil samples from residential properties: 10 in each burn area from properties where debris removal was completed by the Army Corps of Engineers and 10 in each burn area from the yards of standing homes.

Sampling Methodology

At each stop, the team donned vinyl gloves and boot coverings to prevent the spread of contamination and collected five evenly spaced samples with a hand-held tool that takes 4-inch soil cores. At standing homes, we sampled throughout the yard. At destroyed properties, we sampled within the former structure’s footprint, where the federal cleanup crews had cleared debris and scraped up to 6 inches of soil.

Sampling Locations

We sampled within the former structure’s footprint, where the Army Corps had scraped off up to 6 inches of soil. We also sampled throughout the yard at standing homes. This comprehensive approach ensured that our samples were representative of the varying conditions found on each property.

Sample Preparation and Testing

Times journalists mixed these five samples in a lined bucket to create one “composite” sample to be tested in the lab. This sample pattern is designed to account for a wide range of soil conditions on each property and serve as an average, since it is possible that one part of a given property might be fully devoid of metal contamination while another might be heavily polluted. Composite sampling is a common practice in wildfire recovery.

Equipment Sanitization

Between every property, the team sanitized all soil collection equipment with distilled water and wipes, and changed gloves and boot covers — so that no potential toxins could accidentally track from one site to another.

Sample Storage and Testing

We stored the samples in lab-provided jars, and kept the samples refrigerated at 38-40 degrees. At the end of the collection week, our editor drove the samples to BSK Associates, a state-certified environmental testing laboratory that tested soil on behalf of the government following the 2018 Camp fire and 2024 Mountain, Park and Borel fires.

Laboratory Testing

BSK used an Environmental Protection Agency-approved method to test for 17 metals most often studied in post-fire recovery. To do this, BSK used an instrument that sorts out different elements from within the soil by mass and counts the atoms. Since each of these 17 elements has a unique atomic mass — for example, only lead has an atomic mass of 0.34 trillion billionths of a gram — BSK could then determine the concentration of the metals.

Chain of Custody and Methodology Review

At each step of the process, our team and BSK meticulously documented the chain of custody for the samples, creating a record of, at each moment, which individual was responsible for the safekeeping of each individual sample. The Times’ methodology rigorously followed soil-testing practices from previous official post-wildfire efforts. Our team reviewed documents outlining the response for the Camp and Woolsey fires, and spoke with soil-testing experts familiar with the standard methodology for California wildfires.

Participant Selection and Testing Limitations

To find participants, we identified standing properties using the California Department of Forestry and Fire Protection’s damage inspection data and properties that had finished debris removal using the Army Corps’ dashboard. All participants consented to testing on their properties, and their exact addresses have been anonymized. The testing methodology used by The Times is a conservative reading. By using composite samples, high levels of contamination from one part of the property can become diluted by relatively uncontaminated sections elsewhere on the property. Further, due to cost considerations, The Times’ methodology differed from typical postfire soil testing practices in one key way: In previous fires, soil testers would collect multiple composite samples for larger properties, roughly one sample per 500 square feet. Our team took only one composite sample per property, regardless of size.

Results and Implications

The Times found two properties cleared by the Army Corps in Altadena still had contamination above the state’s typical health-based cleanup goals: one arsenic, one lead. Altadena’s standing homes had arsenic, lead and mercury levels above typical cleanup goals, across three of the 10 homes our team tested. The Times found only a single reading above typical cleanup goals in the Palisades: a standing home with high levels of arsenic.

Conclusion

The importance of thorough soil testing after wildfires cannot be overstated. The findings of our investigation highlight the need for rigorous and comprehensive testing to ensure the safety of residents returning to their homes. While our methodology was conservative and followed established practices, the results indicate that some properties may still harbor toxic substances, posing a risk to health and the environment.

FAQs

1. What areas were tested for soil toxins?

   • The testing was conducted in the Eaton and Palisades burn scars, focusing on residential properties that had undergone debris removal by the Army Corps of Engineers and standing homes.

2. How were the soil samples collected?

   • Samples were collected using a hand-held tool that takes 4-inch soil cores, with five samples taken from each property to create a composite sample.

3. What was tested in the soil samples?

   • The samples were tested for 17 metals most often studied in post-fire recovery, using an Environmental Protection Agency-approved method.

4. What were the key findings of the soil testing?

   • The testing found properties with contamination above the state’s typical health-based cleanup goals, including arsenic, lead, and mercury, in both cleared and standing homes.
5. Why is soil testing important after wildfires?
   • Soil testing is crucial to identify potential health risks from toxic substances that may be present in the soil after a wildfire, ensuring the safety of residents and the environment.