The development of a comprehensive exposure assessment strategy for polybrominated diphenyl ethers (PBDEs) for use in observational epidemiology studies.

Background: Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants added to consumer products such as electronics, textiles, polyurethane foam and appliances. They are persistent chemicals increasing in the environment and have contaminated the food chain. Some are endocrine disruptors and toxicological evidence indicates they may increase the risk of certain cancers, including breast cancer. Aims: Our aim was to develop a PBDE exposure assessment strategy for use in epidemiology studies, including the Ontario Environment and Health Study, a population-based case-control study of breast cancer in Canadian women, aged 18-39 years. Methods: To evaluate the routes and sources of PBDE exposures, and their relative importance, the published literature was searched using Medline (1996-2012) and Embase (1980-2010). A Google search was used to identify grey literature. The literature was summarized and exposure sources were prioritized. Previously developed questionnaires and exposure assessment strategies were also reviewed. Results: Dust ingestion, dermal absorption, and hand-to-mouth contact were identified as important routes of exposure. Major dietary sources include poultry, red meat, fatty fish, and fish oils. Occupational sources and air travel contribute to exposure. A questionnaire was developed to obtain occupational and environmental exposures and factors such as housing characteristics. To capture potentially important dietary sources, the Block 2005 food frequency questionnaire was modified, and a PBDE database will be developed. To evaluate absorbed dose, serum and urine will be collected and placed in a Biobank. Serum will be analyzed for PBDE congeners. Plans are underway to collect air, dust, and surface wipes in 51 homes, to be used for validation. Conclusions: A comprehensive exposure assessment strategy allows us to: evaluate associations between PBDE exposures and breast cancer (with serum biomarkers), understand sources of exposure measurement error (based on questionnaires), and identify important sources of human exposure.