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PBDES: TOXICOLOGY UPDATE
Citation:
BIRNBAUM, L. S. PBDES: TOXICOLOGY UPDATE. Presented at 2005 National Forum on Contaminants in Fish, Bethesda, MD, September 18 - 21, 2005.
Description:
Polybrominated diphenyl ethers (PBDEs) have been major commercial products used as flame retardants. While two of the commercial mixtures, Penta and Octa, have either been withdrawn or banned in Europe and the US respectively, the largest volume mixture, Deca, continues to be widely used. The relative congener mix in environmental samples, wildlife, and people rarely resembles that in the commercial products. The Penta mixture is the most ecotoxic, with recent studies demonstrating developmental effects in fish at low water concentrations, and immunological and hormonal effects in wildlife. While the hepatotoxicity of the commercial mixtures has been known for some time, association of the induction profiles of liver enzymes with specific congeners distinct has shown that dioxin-like activities are due to contaminants in the commercial products. Recent studies have focused on endocrine disruption and developmental reproductive and neurotoxicity. The Penta mixture as well as several congeners and/or their metabolites are anti-thyroid, anti-progestin, anti- androgenic, and may be either estrogenic or anti-estrogenic. Penta, BDE 99, and BDE 47 delay puberty and are toxic to both male and female sex organs. Penta, and multiple BDE congeners, including BDE 209, are developmentally neurotoxic impairing sensory and cognitive function as well as sex-dependent behaviors. While the Deca congener is relatively rapidly metabolized, the major lower brominated congeners are very persistent. Recent studies have shown that mice eliminate the PBDEs more rapidly in urine than do rats, suggesting a possible explanation for the wide variation of levels in people. Given the high levels at the upper end of the distribution in Americans, there is little margin of exposure. Major questions concern Deca breakdown, interaction of PBDEs with other persistent chemicals, and the risk of alternative flame retardants. The final IRIS Assessment of four of the major congeners found in wildlife and people, BDE 47, 99, 153, and 209, should be available by mid 2006. (This abstract does not reflect Agency policy.)