Studying Lead in the Environment After the Fires
Conversations After the Fires: Studying Lead in the Environment
Thursday, April 10, 2025
Speakers
Isaac (he/him/they/them) is a first-year PhD student in Geobiology at the California Institute of Technology. Their undergraduate research experience in the Middleton Lab at UC Berkeley included investigating museum collections, remote sensing, and environmental DNA techniques as part of his honors biodiversity research in the Sierra de Manantlán of Western México. Before starting graduate school, Isaac worked as a field technician for the UC San Diego Holway Lab invasive ant eradication project on San Clemente Island and as a project coordinator for the UC Los Angeles Ordway Lab to scope a potential NASA airborne and field research campaign in the tropics. Additionally, Isaac enjoys outdoor excursions, live sporting and music events, and exploring new cafes.
Merritt McDowell (she/her/hers) is a first-year PhD student in planetary science at Caltech. She completed her undergraduate degree in chemistry with a minor in astronomy at New York University, where her research focused on photoactive molecular crystals. At Caltech, she works with Professor Francois Tissot investigating heavy metals in dust in dust deposited from the 2025 Eaton fire in Los Angeles, as well as with Professor Mike Brown exploring surface sputtering on Europa, a Galilean moon of Jupiter. Outside of the lab, Merritt enjoys playing volleyball on campus, reading outdoors, and attending sports events.
Christine Sierra O'Connell, Ph.D. (she/her/ella) is an Assistant Professor of Biological Sciences in the Schmid College of Science and Technology at Chapman University and a Pasadena resident. O'Connell is an ecosystem ecologist and global change scientist whose research focuses on how climate change and global change disturbances are altering terrestrial biogeochemical processes and patterns, particularly in soils. Her current projects include work in tropical forests in Puerto Rico and Costa Rica and, now, work studying the Eaton Fire in Altadena, California.
Francois Tissot is a professor of geochemistry at Caltech. He and his research group carry out elemental and isotopic investigations by combining wet chemistry sample preparation in a clean laboratory environment, precise isotopic analyses using advanced instruments, and interpretation of the data using physically based models. His research ranges from cosmochemistry (i.e., the formation and evolution of the solar system), to geochemistry (e.g., reconstructing redox conditions throughout Earth's history), and in recent years has focused on isotope metallomics, a nascent field using stable isotopes to study human health. Tissot holds a PhD from the University of Chicago.
Key Takeaways
Summary of findings presented by Francois Tissot and Merritt McDowell
- Lead was transported by the plume of smoke coming from the Eaton Fire. It contaminated outdoor and indoor surfaces.
- Significant contamination at toxic levels can occur even miles away from the fire zone (measured up to 7 miles from plume).
- Most indoor surfaces that had not been cleaned showed lead levels above the EPA limits. These concentrations were highest within one meter of a window.
- Cleaning refers to wiping surface with a wet (water) wipe.
- The highest outlier readings have been associated with soldering on windowpanes that predated the fire; for all the other points, the team was not able to identify another main source than the fire.
- About 90 percent of surfaces that had been cleaned after the fire showed lead levels below the EPA limit.
- This indicates that cleaning is often, but not always, effective at removing lead from surfaces.
- Data on cadmium, arsenic, chromium, and other heavy metals follows the same pattern, but in much smaller quantities than lead.
- Levels of lead in tap water remain below the EPA level.
- Learn more in a Q&A with Francois Tissot, and see the full data set here.
Summary of findings presented by Isaac Aguilar
- Collected samples of ashes from outdoor street surfaces in the burn scar and outside the burn scar in the direction of the fire plume.
- Ash you can see; dust, measured by the Tissot Lab, is smaller and you cannot always see it.
- Ashes sampled from the wildland fire, the region in the mountains where no structures burned, showed low levels of lead.
- However, lead was detected in ashes from the regions in Altadena where buildings had burned.
- Ashes were transported in a northeast-southwest direction due to the winds. High lead levels were found in ashes along this direction.
- About five miles southwest of the Altadena burn scar they saw a steep drop off in the concentration of lead in the ashes.
- No asbestos was detected in all ash samples. However, this does not rule out asbestos in dust, debris, or aerosols (particles suspended in air).
Summary of findings presented by Christine O'Connell
- On properties within the burned area, an average of 35 percent of homes had soils with lead levels above the California recommended level.
- All the data is from surface soils that are not slated to be removed (top six inches scraped) by FEMA/Army Corps of Engineer debris removal process.
- There was substantial variation in lead levels even within different areas of the same property.
- On some properties, higher lead levels were found around the area where outdoor grills, heaters, etc. were burned.
- In general, fine soil particles (which are more mobile and therefore readily ingestible) were more enriched with lead than bulk soil samples.
- Based on these results, O'Connell's team is recommending for widespread soil testing for lead; If lead levels are elevated, homeowners should advocate for soil removal and replacement.
- Tried and true method is removing contaminated soil and replacing with new soil, but this is not going to be feasible for many people.
- Consider replacing raised-bed soils, adding mulch or compost that can remediate the lead levels (especially if you grow root vegetables), and testing blood levels of lead in vulnerable people (such as children) as an added precaution.
- Practice habits such as washing hands, wet-mopping indoors, and removing shoes before coming indoors.
- Additional note, in response to questions about how the surface and soil contamination compares to historical data: "There are several studies that have relatively recent soil lead data from across Los Angeles that use data collected before the January 2025 LA Fires. These studies don't have strong spatial coverage within the Altadena and Pasadena Eaton Fire footprint or immediate ash plume, so are not a direct comparison. That said, broadly, yes, urban soils in Los Angeles have been shown to have high variability in lead concentration, especially in relation to how close you are to a freeway or major traffic artery. However, we know that ash from the Eaton Fire was enriched in lead and that ash was transported downwind and distributed on to soils. That, in combination with the Tissot lab's data and data from the LA County Department of Public Health, supports the idea that at least some of the elevated soil lead concentrations we observe are due to the Eaton Fire."
Watch the video recording above for more context and to hear the speakers' answers to audience-submitted questions, including how they are approaching remediation in their own homes.
Related Resources
- Health effects of lead exposure:
- From the World Health Organization
- Children and lead (Centers for Disease Control and Prevention)
- At-home testing: Lead tests recommended by the EPA
- Blood testing for lead:
- Lead Hazard Awareness Project: Housecleaning for Lead Safety (Clean Water Action)
- Information from Sonoma County fire in 2017 related to grown produce after fires (University of California Cooperative Extension)
- Other soil testing and contamination information (not fire-specific)
- Trace Elements and Urban Gardens (University of California)
- Soils in Urban Agriculture: Testing, Remediation and Best Management Practices for California Community Gardens, School Gardens, and Urban Farms (University of California Cooperative Extension)
- Los Angeles County Public Health Fire Safety and Health Information
- Eaton Fire Residents United Contamination Map, which shares results from privately hired testing companies
- LA Wildfire Recovery: Ecological Remediation - Danielle Stevenson
- Ongoing soil testing research projects:
- Contaminant Level Evaluation and Analysis for Neighborhoods (CLEAN) from USC: Anyone in Los Angeles who is concerned about the impacts of the fires on soil may participate in this program, at no cost.
- Community Action Project - Los Angeles (CAP.LA): There is no cost to the homeowner for the sampling or testing, however, completion of this enrollment form does not ensure a sample will be taken due to limited resources.