Environmental contaminants and breast cancer in young women

Breast cancer is the most commonly diagnosed cancer in Canadian women, and it is the leading cause of death in young women. Little is known about the modifiable risk factors for breast cancer and inconsistent findings on the associations between environmental, occupational and dietary risk factors and breast cancer have been reported. These may be explained in part by different etiologies and biological mechanisms for pre- and post- menopausal breast cancers.

Little is known about the risk factors for premenopausal breast cancer, and exposures to environmental pollutants are of concern.  A new group of persistent environmental contaminants has emerged: the brominated flame retardants (which include the polybrominated diphenyl ethers: PBDEs). People are exposed both occupationally and environmentally and little is known about their associated human health risks. These chemicals are increasing in the environment, have contaminated the food chain, have been found in high levels in the environment and fatty fish, are endocrine disruptors and toxicological evidence indicates they may increase the risk of certain cancers.

The study was a population-based incident case control study of approximately 700 women.  Investigators collected health/reproductive/lifestyle information including: socio-demographic profile, ethnicity, physical activity, anthropometric, and reproductive characteristics, family history of cancer, sun exposures, recent weight loss and other factors that may act to confound or modify the relationships between PBDE exposures and breast cancer risk.  A brief residential and occupational history was collected and was based on the histories developed by Harris and colleagues, for the Ontario Health Study and the Canadian Partnership for Tomorrow Project (CPT). Additional exposure questions were created for higher risk occupations including: computer technicians, and workers in electronic warehouses and dismantling plants. Environmental exposure questions were designed to capture major potential sources of exposure to the PBDEs – i.e. exposures through airborne dust particulate, household dust, cleaning, vacuuming, carpeting, and consumer products.

Further, investigators collected blood and urine samples and tested for PBDE concentrations to determine the risk associated with exposures to these compounds.  This work was done in collaboration with Scientists at Health Canada.

This was the first study conducted on the association between breast cancer and exposures to PBDEs. This research helps identify some of the health risks associated with these modifiable exposures, and provides data relevant for the Ontario and Canadian population.