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Matt Rahn was about 200 feet away when flames started climbing up the side of the garage and creeping toward the car inside.

A wildfire researcher with California State University San Marcos, Rahn was at the edge of a fire that would go on to burn 4,240 acres across California’s Amador and El Dorado counties. He was there to study the smoke rising off blackening shrubs and trees. Watching the garage burn, though, he realized that firefighters fending off flames without any real lung protection were inhaling more than airborne remnants of burnt plants.

“Think about the average home, all the chemicals and things that are in there, not to mention all the building materials and furniture,” said Rahn, who also is a member of Temecula’s city council. “That’s when we started really thinking about what happens. What’s in the smoke when you have all that complicated fuel being combusted at the same time?”

That was in 2014, when wildfires burned 568 buildings across the state. Fire season is not yet over this year and the toll already is higher: three people dead and 732 buildings burned. And the state is still recovering from back-to-back years of catastrophic fires that killed 137 people and damaged or destroyed nearly 35,000 buildings.

As climate change primes the West to burn and more people build closer to nature, the question of what’s in the smoke when fires tear through wilderness and homes alike is still far from being answered. Yet the health of those breathing the smoke — like the firefighters battling the flames — depends on real data.

“Right now, we’re trying to keep California from burning down,” said Michael McLaughlin, chief of the Cosumnes Fire Department and legislative director of the California Fire Chiefs Association. “But how do we put emphasis on those that we’re putting between the fire and the communities we’re trying to save?”

“On people’s radar.”

When a wildfire burns through grasslands, forests, and chaparral, the blaze churns out fine airborne particles that can irritate the lungs and have been linked to heart and lung problems, as well as premature death. Deadly gases like carbon monoxide and irritating, potentially cancer-causing chemicals like polycyclic aromatic hydrocarbons mix into the smoke cloud as well.

It’s a complex soup with ingredients that can change depending on the fuel and the ferocity of the fire. And as the chemicals stew in the atmosphere, they continue to react — breaking apart and joining together to create new ingredients to inhale.

Burning buildings and cars typically make up only a small proportion of wildfire smoke, according to Shawn Urbanski, a research physical scientist at the Missoula Fire Sciences Laboratory — but their contributions are starting to capture scientists’ attention. “With these recent fires, it’s really sort of gotten on people’s radar,” Urbanski said.

For folks inhaling smoke far from its source, toxic emissions from burning cars and houses are likely to pose less of a health risk as they’re diluted away. “All the way down in the Bay Area, probably the smoke from the Paradise Fire was pretty much just wood smoke,” said John Balmes, a professor at the University of California, San Francisco.

Of course, wood smoke isn’t benign; researchers as well as reporters at Reveal found increases in emergency room visits for heart and breathing problems after exposure to wildfire smoke. But for people immediately downwind and for the firefighters battling the flames, the metals, carcinogens, and toxic air pollutants rising from burning homes and cars could present an additional hazard. “It definitely is an occupational risk for the firefighters when they’re trying to save buildings, and for community exposures,” Balmes said.

We do know that municipal firefighters battling structure fires in towns and cities can run into heavy metals as well as all kinds of cancer-causing chemicals, like formaldehyde, benzene, and asbestos.

They’re also more prone to getting cancer than the general population, according to a massive study of 30,000 firefighters in San Francisco, Chicago, and Philadelphia. The paper, published in the journal Occupational and Environmental Medicine, reported an increase in certain cancers, including of the esophagus, lungs, mouth and throat, large intestine, and kidney.

There haven’t been any similar long-term epidemiology studies of firefighters battling blazes in the wilderness, according to a deep dive into the scientific literature that was published in the journal Inhalation Toxicology in 2016.

Shorter-term studies, however, have reported small drops in lung function and increased inflammation among wildland firefighters exposed to smoke. Kathleen Navarro is a research industrial hygienist at the National Institute for Occupational Safety and Health who has worked as a wildland firefighter. She estimated in a recent study published in Environmental Research that based on their smoke exposures, wildland firefighters may be at greater risk of dying from lung cancer and cardiovascular disease.

Wildland firefighters also tend to battle conflagrations without any lung protection beyond a bandana or a mask to filter out airborne particles — even when they’re working where wilderness and homes intersect, a junction known as the wildland urban interface.

For structure fires in towns or cities, firefighters typically use a breathing apparatus equipped with a clean air tank that lasts about 20 to 30 minutes, according to Cosumnes Fire Chief McLaughlin. That’s not feasible for wildland firefighters who can end up working long shifts, in treacherous terrain.

That’s why figuring out what’s in the smoke, and what it means for health, is so important, said Jesse Estrada, the department safety officer for the California Department of Forestry and Fire Protection, also known as Cal Fire. “You get exposed to a lot of stuff over the years, and the body takes a beatdown,” he said. “We need to understand what the short term and long term effects are. The only way to know that is to let time pass as they do the research, and truly see what we are facing.”

“It’s just a different landscape.”

One of the people driving this research is Aida Rodriguez, a master’s student working with Matt Rahn at CSU San Marcos. The day after the Kincade fire started in Sonoma County, Rodriguez hopped on a plane with a pink duffle bag full of pre-labeled glass vials, patches made out of the same Nomex material in firefighters’ uniforms, and fabric staplers. Airport security, Rodriguez said, “were concerned about everything in there.”

The next morning, under a reddish haze of smoke on the horizon and the faint smell of camp fires in the air, Rodriguez got to work. Balancing the vials and Nomex patches on the front of a fire engine at the base camp in Santa Rosa, she tacked the material to the outside and the inside of the firefighters’ gear. She was done in about 20 minutes. “I was fast and furiously going through it,” she said.

Twenty-four hours later, it was Rahn who was in charge of ripping the patches from the returning firefighters’ uniforms, pushing them into the glass vials, and mailing them to an independent lab in Ohio for testing. His team’s goal is to find out which chemicals settle on the outside of the firefighters’ uniforms while they’re fighting the flames, and which ones soak through.

“Are they harmful chemicals? Are they cancer causing?” Rodriguez said. “If that’s something we can answer, then you can develop a decontamination protocol to mitigate the exposure to those chemicals.”

Scientists across the country are asking these questions. Amara Holder, a scientist with the U.S. Environmental Protection Agency, is working with the U.S. Forest Service to review what we know — and what we don’t — about the air pollution from fires that burn homes and wilderness together.

The stakes are high for firefighters and other emergency responders, and for the people living close to a conflagration. “You’ve got smoke from a house, or a car, as well as trees,” Holder said. “It’s just a different landscape.”

Key will be measuring what’s in the smoke, and determining how far these pollutants travel — as some might dissipate before they reach nearby towns, and some might not. Figuring that out could help guide evacuations and determine when and where wildland firefighters need to wear protective equipment. “Then we’ll know what we need to do to protect people,” Holder said.

Navarro, the scientist who has worked as a wildland firefighter, is taking an even closer look at wildland firefighter health — by studying their bodily fluids. She and a team of researchers at the University of Miami and the University of Arizona are collecting blood and urine samples from firefighters battling fires at the interface between homes and nature. She’s looking for signs of metals, certain flame retardants, and a family of chemicals called polycyclic aromatic hydrocarbons that’s known to include carcinogens.

In those environments, firefighters’ chemical exposures become much more complex, according to Navarro’s colleague, Kenneth Fent. “There are a lot more questions about their health risks even above and beyond other wildland firefighters where it may be more vegetation exposure,” Fent said.

Fent is helming a voluntary National Firefighter Registry to track the long-term health of any firefighter who signs up. The goal is to understand the long-term cancer risk of firefighters across the field, from those rushing into burning buildings to those fighting to keep a wildfire from engulfing a nearby town.

For wildland firefighters in particular, he said, this is the kind of study that’s been missing. And identifying the risks is the first step for trying to prevent them.

“This is an expensive consideration.”

Why don’t we know yet what long-term health problems might plague wildland firefighters? One reason is logistics: it’s tough for scientists to tag along with firefighters while they’re working in extreme conditions to save lives and homes. “To do my work, I became a firefighter,” Navarro said. Her training allows her to measure smoke exposures at active wildfires, and gives her insights into what the job as a wildland firefighter actually involves.

Another reason is that this research is expensive, according to CSU San Marcos’ Rahn. “The laboratory analysis costs us about $2,000 per firefighter,” he said. “This is an expensive consideration. That’s the hurdle we’re up against.”

And the money — which Rahn said includes a grant from the Federal Emergency Management Agency and another from the Cal Fire Local 2881 union — is running out.

Researchers have struggled to find someone willing to pay to investigate the risks to wildland firefighters, he said. “We have to convince these funding agencies, believe it or not, that the work we do here is not just a California issue — this is a national concern,” he said. “It’s a challenge every year to try to receive that funding.”

That’s why two years ago Cal Fire Local 2881 pushed the state of California to fund the research, according to union President Tim Edwards. And a bill by Sen. Connie Leyva, a Democrat from Chino, would have tapped $5 million from the state’s general fund to pay for wildland firefighting research at California State University campuses.

Although the bill sailed through the Legislature, former Gov. Jerry Brown vetoed it, calling it a “well-intentioned and important proposal” that belonged in the budget, not legislation. Edwards, an engineer with Cal Fire and thyroid cancer survivor, said the veto was disappointing. “Being a state employee, and a state firefighter, I think that hurt me more than anything. It frustrated me more than anything,” he said.

Now, Edwards said the union is working to get the funding included in the state budget. H.D. Palmer, deputy director for external affairs at the California Department of Finance, wouldn’t say whether the union’s latest efforts will work. “I’ll respectfully decline to speculate on what will or will not be included in next year’s budget proposal,” he said.

What’s next?

There are strategies to reduce wildland firefighters’ risks by removing them from the smoke when they’re off shift, and giving them a chance to clean up, Cal Fire’s Estrada said. “It doesn’t mean that when they go out in these environments that 100 percent of the time, every firefighter is completely immersed in the smoke for the duration,” he said.

Still, union president Edwards said, “We’re hoping to eventually find a breathing apparatus that will work at the wildland conditions.”

To that end, the Department of Homeland Security Science and Technology Directorate has contracted with a company called TDA Research to create a lightweight respirator that firefighters can use in the wildland for days to weeks. Since many wildland firefighters wear bandanas over their faces, the device is shaped like a scarf.

“We wanted to create something that was similar to what they use,” said Kimberli Jones-Holt, program manager with the DHS Science and Technology Directorate. Jones-Holt is optimistic that wildland firefighters could be using the device by 2021.

As for Rodriguez, the results aren’t back yet from the patches she sent into the smoke in Sonoma. But in the meantime, she has her glass vials and fabric staplers still packed in that pink duffle bag, ready for the next fire, she said: “It’s important for us to realize that fire season is year round. I don’t really have the time to sit and wait.”

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