Rancho Adobe Fire Capt. Jimmy Bernal won’t receive his individual results for a week or two.

But he’s already heard a recap of preliminary findings from a study of blood and urine samples collected from firefighters after the 2017 Tubbs fire, and it’s enough to make him nervous.

Specimens from 149 Bay Area firefighters deployed to the destructive wildfire yielded elevated levels of mercury, a neurotoxin and carcinogen, and two toxic man-made chemicals, compared to samples from 31 firefighters who stayed close to home.

Principal investigator Rachel Morello-Frosch, a UC Berkeley environmental health researcher, said the findings need to be viewed with caution.

There is not enough evidence to draw direct conclusions about whether substances found in firefighters’ systems reflect exposure sustained during any particular fire or implications for their health, she said.

But release of the study’s initial results this week has nonetheless stoked mounting concerns about firefighters’ exposure to toxins and alarming rates of cancer and other diseases in the profession. Those worries are growing given the proliferation of large wildfires in California at the edges of wildlands and suburban areas, which incinerate organic fuels and man-made materials in their path.

Greater awareness

The tests have implications far beyond the fire service. Morello-Frosch said firefighters are “sentinels of environmental chemical exposure” for anyone else in close proximity — including law enforcement officers who assist with evacuations and security, and civilians who stay behind to defend their homes.

But most firefighters need little reminding, given growing awareness of the risk they face through direct exposure to smoke, and the gases and particles within it.

If they aren’t hearing it through health and wellness training, they’re hearing about it through colleagues.

“When I started, we didn’t talk about firefighters having cancer,” said retired Marin County firefighter Bob Briare, 62, of Larkfield. “At the end of my career, not only did I have cancer, but many of my friends had cancer.”

Said Bernal, 40, “This is the career we chose. But it’s scary, because I have two kids, and I want to make sure I’m there for them.”

The Tubbs fire was one of several wildfires that broke out around the region amid extremely dry conditions and wildly gusting winds the night of Oct. 8, 2017. Until the Camp fire razed the town of Paradise a year later, it was the most destructive in California history, destroying more than 5,600 structures and killing 22 people as it rampaged west from Calistoga through Santa Rosa.

Anyone in the area experienced the caustic smoke that resulted from the blaze, but no one more than the first responders who were directly in the fire’s path — many of them for days on end, inhaling gases and particles from incinerated building materials, household goods, garden products, metals, electronics and all manner of harmless and hazardous substances.

“That was a large exposure,” said Petaluma firefighter Kevin Burris, a cancer survivor at 36. “A normal person would never get exposed to that many structure fires burning at once.”

Bernal remembers how crews worked for days in the noxious fumes, their heads aching, “constantly popping ibuprofen.” Ten Rancho Adobe firefighters would later provide blood and urine samples.