The immediate risks faced by the firefighters who were on the front lines battling the Palisades and Eaton fires that tore through Los Angeles County may have abated, but long-term health concerns remain.

A team of researchers tested the blood of a group of 20 firefighters who were called to duty when the wildfires hit Los Angeles County communities, and found that they had levels of lead and mercury in their blood that was significantly higher than what health experts consider to be safe — and also higher than firefighters exposed to a forest fire.

The results are part of the longer-term LA Fire Health Study, which is investigating the health impacts of the January fires on those exposed to the toxins it released into the the environment. The team includes researchers from the Harvard T.H. Chan School of Public Health, the UCLA Fielding School of Public Health, UC Davis, the University of Texas at Austin, and the USC Keck School of Medicine.

“What you need to worry about is some of these metals that, when they get burned, they get up in the air,” said Dr. Kari Nadeau, chair of the Department of Environmental Health at Harvard T.H. Chan School of Public Health and one of the researchers working on the project. “They can get into your lungs, and they can get into your skin, and they get can absorbed and get into your blood.”

The group of 20 firefighters — who had come from Northern California to assist in the efforts — were tested just days after the fires were contained. They had toiled for long hours as the two fires razed entire communities, burning homes, cars, businesses, and a still unknown list of chemicals and metals. Combined, the fires killed 29 people and destroyed more than 16,000 structures.

On average, said Nadeau, the firefighters had lead and mercury levels three and five times higher, respectively, than a control group of firefighters who fought a forest fire alone. According to the California Department of Public Health, the average blood lead level for adults in the United States is less than 1 microgram per deciliter.

Researchers are still looking to expand the number of firefighters in the study, as well as the range of toxins they may have been exposed to. Nevertheless, even these limited and preliminary findings bolster a growing worry among firefighters that the L.A. fires may have exposed them to metals and chemicals with long-term health effects.

“The results are pretty alarming,” said Dave Gillotte, a captain with the Los Angeles County Fire Department and president of the Los Angeles County Firefighters Local 1014. “We don’t just fear, but we’re quite confident that we’re going to see health impacts with our firefighters who fought these fires on the front lines.”

Firefighters regularly risk exposure to chemicals and metals — including lead and mercury — when responding to house and commercial fires in an urban setting, Gillotte said. But response to a single house fire, for example, would likely last a few hours, not the days on end of the Palisades and Eaton fires. Firefighters also typically face prolonged exposure to the particulate matter in smoke when fighting wildfires in rural areas — but not the chemicals of an urban setting. The Eaton and Palisades fires presented a combined risk: a wildfire-like blaze with firefighters on the ground for extended periods in an urban setting, with electric vehicles, batteries, chemicals and metals burning in high heat, mixing and spreading with the same wind that was spreading the flames.

“It was a more intense exposure as a result of the wind driving those toxins, even with our protective gear,” Gillotte said.

According to Gillotte, these types of urban wildfires could cause long-term health impacts for first responders similar to those from events like the destruction of the World Trade Center on Sept. 11, 2001. Already, officials from the Sacramento Metropolitan Fire District, the Sacramento Fire Department, and Los Angeles County have begun to test their firefighters for metal and chemical exposure, Gillotte said.

Meanwhile, as part of a separate study, Los Angeles city fire officials have also been looking at the health effects on its firefighters.

“We are very concerned and worried,” said Los Angeles Fire Department Capt. Kevin Frank. The LAFD has so far taken blood and urine samples of about 350 of its firefighters, as part of an ongoing nationwide study, funded by the Federal Emergency Management Agency, to look at firefighters’ biomarkers and exposure to cancer-causing substances. That study — which is different than the LA Fire Health Study and the one mentioned by Gillotte — includes more than 7,000 firefighters from across the country.

After the fires, Frank said, several firefighters who reported to Altadena and Pacific Palisades reported health issues, such as trouble breathing. Nadeau, who is working on the LA Fire Health Study, but not the FEMA-funded national study, noted that exposure to heavy metals can contribute to worse long-term health outcomes.

Firefighters already face higher levels of some illnesses, such as autoimmune diseases, asthma and some cancers, she said. Fire officials said the life expectancy of a firefighter is about 10 years lower than that of the average person.

The LA Fire Health study is still in its early stages. Nadeau says she and her colleagues plan to look for evidence of exposure to other heavy metals in addition to mercury and lead. “We’re going to be studying toxins that haven’t been studied” in firefighters before, she said.

Typically, the results of studies like these are not made public until they have been peer-reviewed and published by a scientific journal. Nadeau said the consortium decided to share some of the preliminary data early, hoping to help residents, civic leaders and first responders understand the impacts of the fires.

“You really want to know: ‘What’s in the air, what’s in the water, what’s in the ash that blew into my kitchen cabinet? Do I let my dog outside?’” she said. “All these questions were coming up and we thought, ‘We really need to serve the community.’” Indeed, while the initial findings will be focused on firefighters’ exposure, the team is also looking into residents’ exposure to heavy metals and chemicals.

Nadeau is also looking ahead: The information, she says, could help fire officials as they face the possibility of another similar fire by helping them better understand the source of the chemicals, how safety equipment was used during the fires, and the efficacy of that gear.

“I’d like to say this is the last of its kind, but we know it won’t be,” she said. “It’s not a matter of if, but a matter of when people undergo a fire like that again in L.A.”