New research by Yale has found an association between exposure to chemicals commonly used in firefighting and incidence of a brain tumor called a glioma in firefights, suggesting that the cancer may have an environmental cause.
Glioma is the umbrella term for cancer of the glial cells that help support, protect, and connect nerves. Glioblastoma is a type of glioma. Gliomas are often malignant, occasionally slow-growing brain cancers with significant rates of morbidity and mortality.
Although age and family history are known glioma risk factors, the science around environmental risk factors is limited. However, a new study led by the Yale School of Public Health (YSPH) has highlighted an association between the risk of developing the brain cancer and exposure to chemicals commonly used in firefighting.
“Although glioma is largely associated with mutational processes that correlate with age, our finding that some gliomas have tumor signatures associated with environmental agents, such as haloalkanes, is of great interest given the lack of risk factors previously identified for glioma development,” said corresponding author Elizabeth Claus, MD, PhD, a professor of biostatistics and Director of Medical Research at YSPH.
Haloalkanes are organic compounds widely used commercially and in the home. They can be found in solvents, refrigerants, pesticides, and pharmaceuticals and are used as flame retardants and fire extinguishants. The researchers obtained data on 35 individuals from the University of California San Francisco (UCSF) Adult Glioma Study ,which recruited glioma cases and controls from 1991 through 2013 to identify genetic, developmental, immunological and other risk factors.
The 35 participants comprised 17 firefighters and 18 non-firefighters with glioma, 94% of whom were men. The firefighters had worked on average 22 years in the job and were diagnosed, on average, about seven years after their last reported firefighting exposure. Most participants’ tumors were classified as "IDH1/IDH2 wild type," meaning they didn’t have mutations of the IDH1 or IDH2 genes. These mutations affect how cells process energy and are commonly seen in lower-grade gliomas. So, "wild type" gliomas are likely to be more aggressive and more likely to be glioblastomas, the most severe form of glioma. This fits, as most of the study participants were diagnosed with high-grade tumors and most received treatment by way of chemo- and radiation therapy.
The researchers compared blood and tumor samples from the two groups, searching for "haloalkane-associated mutational signatures." When cells are exposed to haloalkanes, the chemicals can interact with DNA, causing specific types of damage. The cell’s attempt to repair this damage can result in a characteristic pattern of mutations – such as the signature being sought here – which serves as a molecular record indicating past haloalkane exposure.
The researchers found a greater number of haloalkane-associated mutational signatures in the firefighters’ tumors. Interestingly, they also found that several non-firefighters who worked as shipyard workers and painters, jobs that likely exposed them to haloalkanes, also showed evidence of the signature in their gliomas.
“Although intriguing, our study is small and will require confirmation in large samples,” Claus said. “It will also be of interest to explore whether these tumor patterns are seen in other types of cancers in firefighters as well as in persons who may have high exposure to haloalkanes by virtue of their occupation or environment. Identification of exposure risk would be helpful in developing preventive measures.”
In a move that accords with the study’s findings, only days ago Texas lawmakers introduced House Bill 198 (HB 198), which proposes mandatory periodic cancer screening for firefighters following Wade Cannon’s death from job-related colon cancer. Cannon died in 2022 at age 33. In the above video, recorded when he was 31, Cannon speaks about his diagnosis.
If it’s passed, HB 198 would require firefighters to be tested for colorectal, prostate, lung, and brain cancers five years after they begin employment and once every three years after that.
The study was published in the journal Cancer.
Source: Yale School of Public Health
