Polybrominated Diphenyl Ether Exposure and Thyroid Function Tests in North American Adults

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are flame-retardant chemicals that are added to many consumer products. Multiple animal studies have shown PBDEs to be thyroid hormone (TH) disruptors. Epidemiologic evidence of PBDE exposure associated with TH disruption has been inconclusive. OBJECTIVES: We used repeated measures to estimate associations between serum PBDE concentrations and THs in a North American adult cohort. METHODS: From 2010 to 2011, we collected <= 3 serum samples at approximately 6-month intervals from 52 healthy adult office workers from Boston, Massachusetts, for analysis of PBDE congeners and THs. RESULTS: The geometric mean sum concentrations of the most prevalent PBDE congeners (BDE-28, BDE-47, BDE-99, BDE-100, and BDE-153) were 22 ng/g lipid in winter 2010, 23 ng/g lipid in summer 2010, and 19 ng/g lipid in winter 2011. BDE-47 was the predominant congener. Based on a multivariable mixed regression model, we estimated that on average, a 1-ng/g serum increase in BDE-47 was associated with a 2.6-mu g/dL decrease in total thyroxine (T-4) (95% CI: -4.7, -0.35). Total T-4 was inversely associated with each PBDE congener. Serum concentrations of PBDEs were not strongly associated with total triiodothyronine (T-3), free T-4, or thyroid-stimulating hormone (TSH). CONCLUSION: These results are consistent with those from animal studies showing that exposure to PBDEs is associated with a decrease in serum T-4. Because the other TH concentrations did not appear to be associated with BDE exposures, our findings do not indicate effects on the pituitary-thyroid axis. Taken together, our findings suggest that PBDE exposure might decrease the binding of T-4 to serum T-4 binding proteins.