Mixtures of Flame Retardants and Cancer Risk

Background: Thyroid cancer incidence in the U.S. is increasing at a rate faster than any other cancer. Rates in women are three times higher than men. Though the rise is partially due to diagnostic changes, exposures to environmental pollutants such as flame retardants and other poly-halogenated aromatic hydrocarbons (PHAHs), may be playing an etiologic role. These chemicals are used as flame retardants in electronics, furniture, building materials, and pesticides. They are structurally similar to thyroid hormones and can perturb thyroid hormone homeostasis, causing thyroid dysfunction, potentially leading to thyroid gland tumorigenesis. People may be concurrently exposed to numerous halogenated compounds; disentangling which individual chemicals or chemical combinations are most harmful is challenging.

Objectives: Our goals are to evaluate whether individual PHAHs or combinations of PHAHs are associated with increased risk of papillary thyroid cancer in women, a high-risk group, and to evaluate predictors of PHAH exposure. Specifically, we aim to: (1) Investigate the relationship between serum concentrations of individual PHAHs and papillary thyroid cancer risk, (2) Assess joint effects from co-exposures to multiple PHAHs on papillary thyroid cancer risk, (3) Evaluate whether residential proximity to PHAH sources is associated with PHAH serum concentrations and thyroid cancer risk, (4) Evaluate the relationship between concentrations of urinary metabolites of PHAH replacements and serum concentrations of traditional PHAHs, and (5) Investigate the association between urinary biomarkers of PHAH replacements and risk of papillary thyroid cancer in women.

Funding from the American Cancer Society