A new study suggests that from 2000 to 2015, children between ages 0 and 4 and adults between 30 and 34 in Butte-Silver Bow and Anaconda-Deer Lodge counties have an elevated incidence rates of brain and central nervous system cancers compared to the rest of Montana.
Researchers from the Arnold School of Public Health at the University of South Carolina-Columbia examined brain and other central nervous system cancer data from the Montana Central Tumor Registry. They found that brain cancer incidence rates in Deer Lodge and Silver Bow counties were elevated among two age groups, ages 0 to 4 and 30 to 34, compared to all other counties in Montana.
Of the 58 Deer Lodge and Silver Bow county residents diagnosed with brain and other central nervous system cancer between 2000 and 2015, five were children between ages 0 and 4, and six were young adults ages 30 to 34.
The team found no other age group had elevated rates of brain cancer over the 15-year period.
After adjusting for sex, stage of cancer and diagnosis year, the researchers found that “the risk of new cases of brain and other nervous system cancers is estimated to be more than six times as high in (Anaconda-)Deer Lodge and (Butte-)Silver Bow counties compared to other Montana counties.” For adults between ages 30 to 34, the risk was four times higher in the two counties compared to other counties in the state.
The research, published Jan. 6 in Spatial and Spatio-temporal Epidemiology, highlighted that “the risk of brain and other nervous system cancers in very young children and adults in their prime is elevated at a level to cause concern for the residents of these two contiguous counties.”
The authors noted that: “However, without a residential history, we do not know how many of these young adults continuously lived in the DL/SB area. Further research is needed to explore associations between metal exposures and brain and other nervous system cancers, that includes residential history, exposure to radiation, family history of conditions associated with brain and nervous system cancer, and other known risk factors.”
“This study tells you that there is a real high risk in this young age group, and that is really scary,” Suzanne McDermott, professor of epidemiology at USC-Columbia and co-author of the study, told the Montana Standard. “If I were the head of the health department, I would look at starting public health surveillance. I would start monitoring levels of copper, zinc, arsenic and other metals in the blood, urine, hair and nails.”
Karen Sullivan, Butte-Silver Bow public health officer, said Monday that both she and Montana Department of Public Health and Human Services staff reviewed the public health and environmental data available but “do not agree with the conclusions of McDermott and her coauthors.”
Sullivan issued a press release stating that “the state health department analyzed the brain cancer cases used in McDermott’s study, and found that the specific types of brain cancers of the patients in the two age groups cited by McDermott – ages 0-5 and 30-34 – do not point toward an environmental cause or other common cause to all the cases.”
“The study wasn’t designed to show that exposure to heavy metals cause brain cancer,” Sullivan explained to the Standard. “It didn’t measure whether individual patients were exposed to heavy metals.”
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Sullivan said the Butte-Silver Bow Health Department collaborated with the state health department to produce FAQs sheet in response to McDermott’s latest study. The two departments outline several limitations they found in McDermott’s research.
“First, the study was not designed to show that exposure to heavy metals causes brain cancer,” according to the FAQs sheet. “Second, the study did not measure whether individual patients were exposed to heavy metals.” In other words, authors of the study did not have residential history and did not know whether the patients lived outside of Deer Lodge or Silver Bow Counties before their cancer diagnosis, according to Sullivan.
The FAQs sheet also pointed out that the cause of most brain cancers is not fully understood and that exposure to heavy metals is not associated with all types of brain cancer.
“There is little evidence in scientific literature that show that exposure to heavy metals cause brain cancer,” Sullivan explained. “One exception to that is lead.”
According to the Center for Disease Control, some studies suggest that very large exposures to lead may cause glioma, a type of brain cancer.
“I think a another major limitation is that the study combined Butte-Silver Bow and Anaconda-Deer Lodge together,” Sullivan explained. “I understand why Suzanne McDermott and her team combined the two counties, because looking at one county alone doesn’t give a sample size large enough. But how are we in Butte-Silver Bow to know what we have on our hands when the two counties are combined?”
McDermott acknowledged that it would be better to look at Silver Bow and Deer Lodge counties individually; however, her team had to combine the two counties to have a larger sample size.
“These are still very strong results,” McDermott said. She explained that her team’s study does not suggest that there is a causal relationship between exposure to heavy metals and brain cancer.
“It’s reasonable to speculate that it’s causal, but we cannot say there’s a causal link because this is an epidemiological study,” McDermott said. “It’s not about what might’ve happened and what didn’t happen. I don’t know why we saw higher incidence rates in those two age groups. Our study was not to answer the why, but rather show what the data tells us."
On Monday, Sullivan announced that the Butte-Silver Bow Board of Health is proposing to form a committee to review future health studies concerning Butte-Silver Bow residents.
“If researchers are telling us about a public health emergency or if there is a call for public health action, this committee could advise me and other public health officials on what that action would look like,” Sullivan said.