Research reveals extensive LA-area fires altered blood proteins in firefighters, raising health concerns

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.”