A new study has shown that among patients diagnosed with glioma, the most common form of malignant brain cancer, certain genetic mutations are more common in firefighters than in people with other occupations. These mutations had been previously linked to exposure to haloalkanes, chemicals that are commonly used as flame retardants and fire extinguishers.

This is the first study to confirm exposure to haloalkanes is a potential risk factor for developing glioma, a type of brain cancer that is especially hard to treat. 

“This is one of the few preventable environmental risk factors for glioma that have been identified,” said Elizabeth Claus, professor at the Yale School of Public Health, who led the research.

“Despite the fact that I and many others have studied this for many years, we have found very little in terms of preventable risk factors for glioma. That’s different from a lot of other cancers, like breast, lung, or ovarian cancer, and even other brain tumors, where there are known environmental risk factors.”

Looking for potential environmental effects, her research team collected samples from the tumors and blood of firefighters diagnosed with glioma. They found a much higher rate of certain mutations when compared to glioma patients without a history of firefighting.

Claus sees these results as an important step towards understanding how haloalkanes can affect our health in the long term. She believes this research should inform public health intervention strategies to avoid occupational hazards of working with these compounds.

Unraveling genetic signatures

In a previous study, Claus and colleagues had analyzed over 1,000 samples of glioma to look for mutations that could be linked to either genetic or environmental risk factors. One of their findings was that a fraction of these tumors showed mutation patterns that other researchers had linked to exposure to haloalkanes before.

“In a Japanese printing factory, they found a very large number of tumors of the bile duct,” said Claus. “They knew these workers had been exposed to these chemicals and were suspicious there was a tie between cancer and haloalkanes.”

That study had shown that cells exposed to haloalkanes developed the same type of mutations found in the office workers, drawing a direct link between them. These mutations do not affect a specific gene — while they may appear anywhere in our DNA, they happen following specific patterns that act as a “signature” that can give us clues about what caused them.

However, Claus and colleagues didn’t have any data regarding the occupational history of the participants in their initial study. To confirm this potential link, the researchers analyzed samples from 17 firefighters diagnosed with glioma that had taken part in a 30-year long glioma study at the University of California, San Francisco. On average, the participants had worked as firefighters for 22 years.

The researchers compared their tumor and blood samples to those of 18 glioma patients with other occupations, and found a much higher rate of the haloalkane mutation signature in the firefighter group. The longer the person had worked as a firefighter, the more likely they were to carry more of these mutations.

What’s more, among the non-firefighter participants, those who showed higher rates of these mutations were more likely to have jobs where they could possibly be exposed to haloalkanes, such as car painting and machine maintenance. “We got a little hint that there are other occupations that may be at risk as well,” said Claus.

Towards better prevention strategies

Claus hopes this research will ultimately benefit people diagnosed with glioma, a condition that has seen limited medical progress in the past decades: “We have not found much that has helped us to treat these patients better than we did 40 years ago.”

While the study only had 35 participants, Claus believes these preliminary results provide valuable insights into potential risk factors for glioma, especially as the participants had a long history of firefighting experience.

“These are firefighters that had very heavy exposure [to haloalkanes] over the years, which makes them an important group to study long-term effects,” said Claus.

The study also highlights the importance of implementing prevention strategies at the workplace. Many of the firefighters in the study had been diagnosed over 10-15 years ago, back when protection against haloalkanes was limited compared to today.

“It’s not just about having the right equipment, but also about using it properly,” said Claus, who recalled interviews with firefighters who had, for instance, regularly eaten at the firehouse right next to contaminated equipment.

Fortunately, as the public has grown increasingly aware of the toxicity of haloalkanes, the equipment and safety protocols available to firefighters have gotten much better over the past decade, she added.

However, other occupations may also be at risk of haloalkane exposure. These can include anything that involves handling pesticides, paint and paint removers, coatings, refrigerants, and adhesives.

“We’re hoping to follow up with a larger study including occupations where it is not well known that workers are exposed to these toxins,” said Claus. She pointed at the example of shipyard workers or car painters, who can be regularly exposed to these compounds but are rarely protected against them.

Reference: Vincent L. Cannatori et al., Glioma mutational signatures associated with haloalkane exposure are enriched in firefighters, Cancer (2025). DOI: 10.1002/cncr.35732

Feature image credit: Hush Naidoo Jade Photography on Unsplash