Study Examines Breast Cancer Link To Flame Retardants

Polybrominated diphenyl ethers are used in clothing

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Shelley Harris

Probing links between breast cancer and a group of pollutants is the purpose of a new $846,000 study involving researchers from U of G, Toronto and Ottawa.

The team has received a three-year grant from the Canadian Cancer Society Research Institute to look at brominated flame retardants, a suspected risk factor for breast cancer. The researchers hope to pin down the role of polybrominated diphenyl ethers (PBDEs) in the disease.

“This will be the first population-based study conducted on the association between breast cancer and environmental exposures to PBDEs,” says Len Ritter, professor emeritus in the School of Environmental Sciences. He retired in 2011.

He hopes the study will help identify health risks of exposure to these pollutants and, ultimately, help in preventing the disease and reducing exposure.

Breast cancer is the most prevalent form of cancer in western women followed by lung cancer. Despite that, he says, “we don’t know much about risk factors,” including age of first pregnancy and whether or not a woman breastfeeds.

About 24,000 new cases of breast cancer occur every year in Canada. The disease claims about 5,100 lives every year.

The research team plans to focus on PBDEs, used as flame retardants in products such as clothing and computer keyboards. These chemicals are spreading in the environment, where they have entered the food chain, particularly in fatty fish.

They are known to affect endocrine function. Earlier evidence shows they may increase the risks of certain cancers, says Ritter. Because the compounds are long-lasting, researchers can look at historical exposures.

The team will examine links between PBDEs and the risk of breast cancer in women aged 18 to 39 included in the Ontario Cancer Registry. They aim to look at sources of these chemicals in food, the environment and workplaces. They will collect and store blood and urine samples for future biomarker studies.

By comparing exposures in those women and a control group without the disease, the researchers hope to connect these pollutants with breast cancer – what Ritter calls the “fingerprint” of PBDEs.

The grant’s principal investigator is Shelley Harris, a scientist in prevention and cancer control at Cancer Care Ontario and a faculty member in the University of Toronto’s Dalla Lana School of Public Health.

She completed her master’s degree in U of G’s former environmental biology department with professor emeritus Keith Solomon. (Her father, Ron Harris, chaired that department and recruited Ritter from Health Canada in 1993.) She completed her PhD at the University of Toronto.

Pointing to public concern about exposure to environmental chemicals, she says: “We know that a number of these chemicals increase the risks of cancer but know very little about the effects of the brominated flame retardants in humans.

“This type of research on emerging environmental contaminants is very expensive to conduct, and rarely is it funded in Canada. We have a great opportunity here to do groundbreaking work.”

The team includes Ritter, additional scientists at Cancer Care Ontario, and researchers at Health Canada in Ottawa and the Samuel Lunenfeld Research Institute in Toronto.

Says Ritter, “We are not going to solve breast cancer, but we may identify significant risk factors.”

Genetics accounts for only about four per cent of risk factors for breast cancer, including variations in BRCA1 and 2 genes. “If you have these genes, you are at much higher risk of getting breast cancer, but the percentage with those genes is very small,” he says.

Earlier, he and Harris worked together on the environmental and occupational health component of an Ontario study looking at risk factors in chronic disease.

Says Harris: “We have developed a very successful collaboration and hope to develop a very strong research program in environment and cancer for the province of Ontario. Not only do we share research interests, but we both have been touched by breast cancer in our families.”