Extensive LA-area fires altered blood proteins in firefighters, raising health concerns
A new study found that firefighters exposed to the Palisades and other fires had changes in their immune system and inflammatory response protein pathways.
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Melissa Furlong is an assistant professor at the Mel and Enid Zuckerman College of Public Health and a member of the Center for Firefighter Health Collaborative Research. |
Credit: Photo by Kris Hanning, U of A Office of Research and Partnerships
Researchers at the University of Arizona Mel and Enid Zuckerman College of Public Health found that firefighters who battled the massive urban fires in the Los Angeles area in January 2025 developed physiological changes that may increase their risk of diseases, including cancer.
The research, which was published in the Journal of Occupational and Environmental Medicine, found changes in blood proteins in firefighters who responded to the January Los Angeles-area blazes, which torched more than 23,000 acres and forced more than 100,000 people to evacuate their homes. The massive fires started in the wildland-urban interface and burned into urban areas, resulting in urban conflagrations.
Researchers compared blood samples taken from 42 firefighters enrolled in the Fire Fighter Cancer Cohort Study from before and after they fought numerous massive fires around Los Angeles. The team found 60 changes in the firefighters’ serum proteome, which are a group of blood proteins that affect multiple systems in the body, including the immune system and inflammatory response.
Other changes to the protein pathways identified in the study included those affecting cancer growth and signaling, metabolic and oxidative stress levels, and the ability of cells to form barriers.
“In this study, we wanted to get a big picture of what the health effects were for the firefighters who were responding to wildland-urban interface fires. We decided to look at changes in blood protein signatures,” said first author Melissa Furlong, an assistant professor of environmental health sciences at the Zuckerman College of Public Health and a member of the Center for Firefighter Health Collaborative Research. “Our research identified changes in proteins that were concerning for lots of different reasons. They indicated a broad suite of possible health effects from exposure to these large urban conflagration fires. These were particularly bad fires, given the amount burned and the length of time.”
Senior author Dr. Jeff Burgess has been collaborating with firefighters on health and safety research since 1992 with a focus on cancer risk and prevention since 2015. Some of his previous research with firefighters identified epigenetic changes linked to health risks, including cancer, and provided evidence that helped support the international classification of firefighting as carcinogenic.
“This publication comes from collaborative research with the fire service, where they have worked with us during all parts of the study,” said Burgess, who founded the Center for Firefighter Health Collaborative Research and is a professor at the Zuckerman College of Public Health and a U of A Cancer Center member. “The results help answer some of the questions from firefighters, which include whether their exposures may put them at risk for future illness.”
Furlong, Burgess and others are working on long-term follow-up studies with firefighters to find ways to help prevent the development of diseases.
“We know that firefighters are at increased risk for lots of different cancers, and what we are hoping is that if we can continue to do this kind of research, then maybe we will be able to identify specific proteins that continue to respond to firefighting exposure over time, regularly,” said Furlong, who also is an associate member of the Cancer Center. “If we can replicate this and see consistent signals, then hopefully we’ll be able to identify proteins that we can intervene on or biomarkers that could potentially be targeted for prevention.”
Additional U of A co-authors included Shawn Beitel, research program administration officer for the Firefighter Health Collaborative Research Program; Reagan Conner, research professional and PhD student at the Department of Community, Environment and Policy at the Zuckerman College of Public Health; and Xinxin Ding, head of the Department of Pharmacology and Toxicology at the R. Ken Coit College of Pharmacy.
Journal
Journal of Occupational and Environmental Medicine
Method of Research
Observational study
Subject of Research
People
Article Title
Changes in Serum Proteins in Firefighters Responding to the 2025 Los Angeles Urban Conflagrations
UW-led study links wildfire smoke to increased odds of preterm birth
About 10% of American babies are born prematurely. Birth before 37 weeks can lead to a cascade of health risks, both immediate and long-term, making prevention a vital tool for improving public health over generations.
In recent years, researchers have identified a potential link between wildfire smoke — one of the fastest-growing sources of air pollution in the United States — and preterm birth, but no study has been big or broad enough to draw definitive conclusions. A new study led by the University of Washington makes an important contribution, analyzing data from more than 20,000 births to find that pregnant people who are exposed to wildfire smoke are more likely to give birth prematurely.
“Preventing preterm birth really pays off with lasting benefits for future health,” said lead author Allison Sherris, a UW postdoctoral researcher in environmental and occupational health sciences. “It’s also something of a mystery. We don’t always understand why babies are born preterm, but we know that air pollution contributes to preterm births, and it makes sense that wildfire smoke would as well. This study underscores that wildfire smoke is inseparable from maternal and infant health.”
In the study, published Nov. 3 in The Lancet Planetary Health, researchers used data from the Environmental influences on Child Health Outcomes (ECHO) program, a federal research project focused on how a wide range of environmental factors affect children’s health. The sample included 20,034 births from 2006-2020 across the contiguous United States.
Researchers estimated participants’ average daily exposure to fine particulate matter, or PM2.5, generated by wildfire smoke, and the total number of days they were exposed to any amount of smoke. They estimated the intensity of smoke exposure by how frequently participants were exposed to wildfire PM2.5 levels above certain thresholds.
They found that pregnant people exposed to more intense wildfire smoke were more likely to give birth prematurely. In mid-pregnancy, exposure to any smoke was associated with an elevated risk of preterm birth, with that risk peaking around the 21st week of gestation. In late pregnancy, elevated risk was most closely associated with exposure to high concentrations of wildfire PM2.5, above 10 micrograms per cubic meter.
“The second trimester is a period of pregnancy with the richest and most intense growth of the placenta, which itself is such an important part of fetal health, growth and development,” said co-author Dr. Catherine Karr, a UW professor of environmental and occupational health sciences and of pediatrics in the UW School of Medicine. “So it may be that the wildfire smoke particles are really interfering with placental health. Some of them are so tiny that after inhalation they can actually get into the bloodstream and get delivered directly into the placenta or fetus.”
The link was strongest and most precise in the Western U.S., where people were exposed to the highest concentrations of wildfire PM2.5 and the greatest number of high-intensity smoke days. Here, the odds of preterm birth increased with each additional microgram per cubic meter of average wildfire PM2.5.
It’s possible those results were more precise simply because the West experiences more wildfire smoke on average, making the exposure model perform better, Sherris said. But there may be other factors behind the regional differences.
The composition of wildfire smoke is different across the country. In the West, smoke tends to come from fires nearby, while in places like the Midwest, smoke has typically drifted in from faraway fires. Smoke’s toxicity changes as it ages and reacts with sunlight and airborne chemicals, which could have affected the results. Researchers also noted that external factors like co-occurring heat or housing quality may have effects that aren’t fully understood.
Researchers hope that future studies will examine the exact mechanisms by which wildfire smoke might trigger preterm birth. But in the meantime, Sherris said, evidence for a link is now strong enough to take action.
“There are a couple avenues for change,” Sherris said. “First, people already get a lot of public health messaging and information throughout pregnancy, so there’s an opportunity to work with clinicians to provide tools for pregnant people to protect themselves during smoke events. Public health agencies’ messaging about wildfire smoke could also be tailored to pregnant people and highlight them as a vulnerable group.”
Co-authors include Logan Dearborn, doctoral student of environmental and occupational health sciences at the UW; Christine Loftus, clinical associate professor of environmental and occupational health sciences at the UW; Adam Szpiro, professor of biostatistics at the UW; Joan Casey, associate professor of environmental and occupational health sciences and of epidemiology at the UW; Sindana Ilango, postdoctoral fellow of epidemiology at the UW; and Marissa Childs, assistant professor of environmental and occupational health sciences at the UW. A full list of co-authors is included with the paper.
This research was funded by the Environmental influences on Child Health Outcomes (ECHO) program at the National Institutes of Health under multiple awards. A full list of ECHO funding awards is included with the paper.
For more information or to contact the researchers, email Alden Woods at acwoods@uw.edu.
Journal
The Lancet Planetary Health
Method of Research
Data/statistical analysis
Subject of Research
People
Article Title
Wildfire-specific fine particulate matter and preterm birth: a US ECHO Cohort analysis
Article Publication Date
3-Nov-2025
COI Statement
AEH was a member of a data safety and monitoring board for a treatment trial of blood pressure management at the University of Pittsburgh. ARS consulted for UNICEF on an analysis of child exposure to pesticides. CJK received an honorarium from Kaiser Permanente to present for paediatricians on wildfire smoke and child health, and received an honorarium and travel support from California Chapter 2 of the American Academy of Pediatrics to present on provider medical education related to air pollution and child health. CTM was chair of a data safety and monitoring board for a US National Institutes of Health (NIH) study, Safety of Sildenafil in Premature Infants with Severe Bronchopulmonary Dysplasia (SILDI-SAFE), and member of a data safety and monitoring board for the Pragmatic Research on Diuretic Management in Early BPD (PRIMED) Study. CTM also received annual fees and royalties as a peer reviewer for UpToDate, and honoraria for lectures including at an Endowed Lectureship at the University of Illinois in March, 2024, the Vermont Oxford Hot Topics Meeting in December, 2024, and the Mednax Center for Research, Education, Quality and Safety Annual Conference for Neonatology in February, 2025. DH was a member of an advisory committee for the Targeting Environmental Neurodevelopmental Risks Project. JA served on the Avera Health Institutional Review Board. RJS has received funding support from the Bia-Echo Foundation. RJS also consults for Linus Technology, and consulted for the Beasley Law Firm until March, 2023. RJS also received travel support to serve on the Observational Study Monitoring Board for the Healthy Brain and Child Development (HBCD) Study, to present at the BC Lung Foundation Air Quality & Health Workshop 2025 (April, 2025), to present at the Japan Society of Endocrine Disruptors Research Meeting (December, 2024), to present at the Society for Birth Defects Research and Prevention 64th Annual Meeting (June, 2024), and to present at the 35th Annual Meeting of the Organization of Teratology Information Specialists (June, 2023). All other authors declare no competing interests.
