On January 7, 2025, two large firestorms in Los Angeles forced many residents to evacuate and burning homes, vehicles, and industrial and commercial buildings.

The Palisades and Eaton fires torched more than 50,000 acres, destroyed 16,000 dwellings, displaced 150,000 residents and devastated the lives of many Southern Californians. Moreover, the massive blazes produced thick fogs of fine particulate matter, heavy metals, volatile organic compounds, carbon monoxide, nitrogen oxides and persistent organic pollutants. Urban fires release more toxins than brush fires due to the lead and asbestos in older buildings.

Through Project Firestorm, a team of researchers from the Keck School of Medicine of the University of Southern California (USC) has embarked on a study of how the fires affected people’s physical and mental health.

“We’re trying to understand the initial effects of the exposures of the urban wildfires, and then we will follow some people up over a longer period to further analyze those exposures,” said Frank Gilliland, MD, PhD, Professor of Population and Public Health Sciences, and an air pollution research expert who is leading the project.

The study leverages the existing health data of 9,000 USC personnel to assess the mental and physical health impacts of the fire. The study, which has been ongoing since the COVID-19 pandemic, aims to follow participants for a year, with a sub-cohort of 200 households for a longer-term exposure analysis.

The project is funded by the Southern California Environmental Health Sciences Center, Southern California Clinical and Translational Science Institute (SC CTSI), and the Hastings Foundation. Jennifer Unger, PhD, Professor of Population and Public Health Sciences, and Daniel Soto, EdD, MPH, Assistant Professor of Clinical Population and Public Health Sciences, worked with Gilliland on the study. The team also recently received an R21 grant from NIH to continue the research and analyze the samples.

“For people who were affected by evacuation, there are issues around mental health, and that’s a problem that needs addressing,” Gilliland added.

Preliminary findings highlight significant mental health issues. Many forced to evacuate experienced anxiety, which appeared to diminish quickly. However, mental health effects, including PTSD and depression, persisted long after evacuations ended, and the initial anxiety subsided.

The research team will study participants’ hair samples to reconstruct a timeline of individuals’ exposure to harmful substances during and after the wildfire. Hair grows at a predictable rate (about a centimeter per month), and substances such as heavy metals and chemicals are incorporated into the hair as it grows. Analyzing different segments of hair enable researchers to identify periods of high exposure to hazards, both during the fire and the cleanup phase.

“A blood sample is a snapshot at one period of time, but the hair sample could provide us with an integrated time measurement to see what the whole exposure profile looks like,” said Gilliland.

The researchers will examine potential correlations between substance and smoke exposures with subsequent health outcomes, including both acute and chronic effects. With these findings, scientists could explore differences between short-term exposure spikes and ongoing, lower-level exposures that may contribute to long-term health issues.

On another front, a major community science project targeting the Eaton firestorm is revealing the damaging impacts of urban wildfire and supporting residents in receiving the local, science-based information they need.

Nicole Maccalla, PhD, an Altadena resident and Director of Evaluation and Improvement at SC CTSI, is applying skills that she uses as a data scientist to conduct research with the Eaton Fire Residents United (EFRU).

EFRU is documenting and addressing contamination, including collecting and mapping test results, advocating for the community and tracking remediation efforts. EFRU has published a dataset and map visualizing the results of commercially conducted contaminant tests, some of which were paid for by residents’ insurance. Tests typically cover wildfire debris—including ash, asbestos, soot, and char — as well as 17 heavy metals, such as lead and arsenic.

“This information is usually known only to the homeowner, the insurance company, and the company that did the testing,” Maccalla said. “We’ve created a safe and secure system for file exchange and consent so that folks can share their tests with us. This is the first time in wildfire history that a community has come together and created a metadata set using a citizen science approach.”

Many residents struggle to access insurance coverage, testing and remediation services. The group is working with 40 organizations to help residents navigate these systems and advocate for clear, science-based standards.

The group partners with universities and research teams, inviting them to present their findings at community speaker nights and events. This process ensures a two-way feedback loop, sharing scientific research with the community and communicating community needs and concerns back to scientists.

“This is a hard recovery for the community, and we’re here to help in that process and connect you to any resource that you might need,” Maccalla added.

As for future directions for fire-related research, EFRU plans to release a post-remediation contamination map that will demonstrate the extent to which various indoor remediation efforts are eliminating toxins from homes. In partnership with Resilient Palisades and the Centre for Applied Ecological Remediation, they launched the Fire-Resilient Bioremediation and Landscape Recovery Consortium to provide information and resources on soil remediation. In addition, EFRU will continue hosting speaker events to bring public health information to the community.