Empowering Resilience: Community Science in the Wake of the 2025 Los Angeles Fires

The smell of smoke lingered in the air for weeks, a quiet reminder of what the community had endured. Even as ash settled into neighborhoods, playgrounds, and gardens, signs of resilience emerged — neighbors helping neighbors, families returning home, and a shared determination to rebuild and heal. After coming to graduate school in Los Angeles, I’ve now witnessed first-hand how destructive and life-altering urban wildfires can be. The 2025 Los Angeles wildfires were a deeply challenging and painful chapter for many — and as I found myself drawn into the urgent task of understanding the risks left behind in the soil beneath our feet, it became clear that the need for community-driven science had never been more pressing.

My name is Cat Odendahl and I’m a PhD candidate in the Earth Sciences Department at USC. I study metals in the environment, particularly metals like lead that persist long after a fire has passed. My dissertation focuses on how metals are essential to life, but also at high concentrations can become hazardous, especially to humans. The 2025 fires created an unprecedented need for rapid response community science, and that’s how I became involved with the Contaminant Level Evaluation and Analysis for Neighborhoods (CLEAN) Project: a community-led effort to test urban soil for lead contamination after wildfires.

What Wildfires Leave Behind

The 2025 fires burned through both the natural and urban environments of Los Angeles. Unlike forest fires in remote regions, these urban wildfires consumed homes, cars, fences, and infrastructure — materials full of chemicals and heavy metals. When these man-made structures burn, they don’t just produce smoke and ash — they release harmful substances that can settle into nearby soils.

Lead is one of the most concerning of these substances. It doesn’t break down in the environment, and exposure — especially for children — can have lifelong health impacts. After a fire, contaminated ash can be transported by wind or rain, making it possible for lead to travel far beyond the burn zone and into communities that were never directly in the fire’s path.

Going Into the Burn Zone

In the weeks following the fires, I visited parts of the burn zone to collect samples for a class. Seeing the devastation up close — burned trees, scorched structures, blackened soil — was a powerful reminder that wildfires don’t end when the flames go out. Residents returned home not just to rebuild their houses, but to face uncertainty about whether the soil around them was safe.

Our class went sampling as frequently as it was safe to after the fires stopped burning. The data that we started to get was not only of interest to us as scientists, but to those who were wondering if going back to their homes was safe. My PI, Seth John, kept getting phone calls and emails from folks impacted by the fires asking if there was contamination present. After quite a bit of chatting with the community about how we can help as a geochemistry lab, we decided to pursue a community-based effort to test soil in and around the burned area.

CLEAN: Contaminant Level Evaluation and Analysis for Neighborhoods After Wildfires

That’s where the CLEAN Project comes in. CLEAN started as a collaboration between a couple of PIs at USC and USC Dornsife Public Exchange who wanted to address a gap in post-wildfire recovery: understanding and communicating the risks of soil contamination. 

This project was unique to everyone involved. Most of the time an academic’s research is only of interest to them and a handful of other academics, usually never reaching the public in a directly impactful way. But this was not the case here.

We created a survey where participants can obtain a Sample ID, anonymizing their sample vs. other samples. We then use this unique Sample ID to post results in a public facing spreadsheet and map. We also created an email, to be able to directly communicate with residents and help guide them through the process. These tasks were all very new to everyone on the team, and we’re still learning as we go!

As someone studying metals and their cycling in the environment, the CLEAN project immediately resonated with me. It was a chance to apply my scientific training to something tangible, urgent, and deeply rooted in environmental justice. I stepped up to create and lead the research team, and quickly found myself immersed in everything from sample processing to analysis to communicating directly with those impacted by the fires.

Our Methods and Impact

To analyze the soil samples, we use an X-ray fluorescence (XRF) spectrometer, which allows us to quickly assess the concentration of lead in a sample. It’s non-destructive and fast, making it a perfect tool for rapid community-scale screening. Each sample only takes 15 seconds to run!

So far, we’ve received thousands of samples from across Los Angeles. 90% of the samples we have analyzed are below the EPA soil screening level of 200 parts per million (ppm). These findings help empower residents with the knowledge they need to protect themselves and their families. This testing service that we provide is free, making it accessible to anyone who fills out our survey.

We’re also interested in the concentration of lead in roadside dust over time after the fires, and this project is called Temporal Resampling and Analysis of Contaminants in the Environment (TRACE). This will help us understand not just where lead ends up immediately after a fire, but how concentrations change over time as it moves through the environment. Does the concentration change differently inside vs. outside the burn zone? Does it stay locked in place? What are the sources and sinks of lead to roadside dust? These are the kinds of questions we’re working to answer.

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None of this would be possible without the support of the Wrigley Institute Graduate Fellowship. The fellowship has given me the resources and community to pursue this work — not just financially, but intellectually and personally. It has connected me with other researchers across disciplines who care deeply about sustainability, resilience, and justice. It’s also helped fund critical components of the project, from lab supplies to field work essentials.

I also want to shout out all of my dedicated and hardworking undergrads who have been helping me run this project. Zach Alvarez, Jessica Guerrero, Lauren Hechinger, Nicolas Lam, and Laura Zhang have helped me to process and organize samples, as well as perform analysis on the XRF. This project would not have been successful without their commitment!

Perhaps most importantly, the fellowship has given me time — time to think, collaborate, and grow into the kind of scientist I want to be. One who listens as much as she tests, and who sees environmental research not as an abstract pursuit, but as a tool for real-world change.

Catherine Odendahl is supported by the USC Dornsife Wrigley Graduate Fellowship.