Bioaccumulation, Metabolism, and Biological Responses to Firemasters(RTM) 550 and BZ-54

Abstract

Firemaster® 550 is a replacement for Penta- formulations of polybrominated diphenyl ether (PBDE) flame retardants. This formulation includes 2,3,4,5-tetrabromo-ethylhexylbenzoate (TBB), 2,3,4,5-tetrabromo-bis(2-ethylhexyl) phthalate (TBPH), triaryl phosphate isomers, and triphenyl phosphate. TBB and TBPH have been measured in several environmental matrices, including but not limited to freshwater sediment and marine mammals. However, few studies have assessed their environmental fate or impact. In this thesis, bioavailability, metabolism, and biological responses of TBB and TBPH were investigated in a variety of toxicological model species. Long-term dietary studies were conducted with fathead minnows (Pimephales promelas). TBB and TBPH bioaccumulated in the fish tissues and debrominated metabolites of TBB were observed. Hepatic DNA damage increased during the exposure, but quickly returned to background levels after the exposure ceased. Exposures were also linked to decreased sperm density in the fathead minnow. Incubations of hepatic sub-cellular fractions (e.g., S9, microsomes, cytosol) with Firemaster® BZ-54 were used to determine species specificity of TBB and TBPH metabolism. TBB was metabolized by the fathead minnow, common carp (Cyprinus carpio), and mouse (Mus musculus, wild type); but not in the snapping turtle (Chelydra serpentina serpentina). All species examined exhibited a reduction in TBPH, but there were no observable metabolites which suggest that some metabolites may not be effectively extracted using these techniques. Bioaccumulation of TBB and TBPH from sediments was evaluated over 28 days using the California blackworm (Lumbriculus variegatus), and chironomid (Chironomus tentans). Biota Sediment Accumulation Factor values of TBB and TBPH in the blackworms were less than those previously reported for Penta-BDEs, the fire retardant formulation these Firemaster® chemicals replaced. In chironomids, TBB bioaccumulated to a greater extent than TBPH. These results indicate that bioaccumulation may be a significant transport pathway by which TBB is transported from the aquatic environment as the chironomids emerge as flies. In conclusion, this work has demonstrated that components of Firemaster® 550 are capable of bioaccumulation, metabolism, and adverse effects in aquatic organisms. Future studies will need to focus on effects resulting from exposure to environmentally relevant concentrations of TBB and TBPH, further elucidation of their metabolism, and evaluation of the effects of contaminated emergent insects on birds.