Firemaster® 550 and Firemaster® BZ-54 are two brominated formulations that are in use as replacements for polybrominated diphenyl ether (PBDE) flame retardants. Two major components of these mixtures are 2,3,4,5-tetrabromo-ethylhexylbenzoate (TBB) and 2,3,4,5-tetrabromo-bis(2-ethylhexyl) phthalate (TBPH). Both have been measured in environmental matrices; however, scant toxicological information exists. The present study aimed to determine if these brominated flame-retardant formulations are bioavailable and adversely affect DNA integrity in fish. Fathead minnows (Pimephales promelas) were orally exposed to either FM 550, FM BZ54, or the nonbrominated form of TBPH, di-(2-ethylhexyl) phthalate (DEHP) for 56 d and depurated (e.g., fed clean food) for 22 d. At several time points, liver and blood cells were collected and assessed for DNA damage. Homogenized fish tissues were extracted and analyzed on day 0 and day 56 to determine the residue of TBB and TBPH and the appearance of any metabolites using gas chromatography-electron-capture negative ion mass spectrometry (GC/ECNI-MS). Significant increases ( p<0.05) in DNA strand breaks from liver cells (but not blood cells) were observed during the exposure period compared with controls, although during depuration these levels returned to control. Both parent compounds, TBB and TBPH, were detected in tissues at approximately 1% of daily dosage along with brominated metabolites. The present study provides evidence for accumulation, metabolism, and genotoxicity of these new formulation flame retardants in fish and highlights the potential adverse effects of TBB- and TBPH-formulated fire retardants to aquatic species.

Firemaster® BZ-54 is a flame retardant additive and consists of a brominated benzoate (2-ethylhexyl 2,3,4,5-tetrabromobenzoate; TBB) and a brominated phthalate (bis (2-ethylhexyl) 2,3,4,5-tetrabromophthalate; TBPH). Previous research has shown that fathead minnows exposed in vivo to Firemaster® BZ-54 accumulate TBB and TBPH. This study examined the in vitro biotransformation potential of TBB and TBPH in hepatic subcellular fractions (i.e., S9, microsomes and cytosol) in the fathead minnow, common carp, mouse and snapping turtle. Metabolism was evaluated by measuring the loss of the parent TBB or TBPH and identifying potential metabolites in the sample extracts. Metabolic loss of TBPH was measured for all species, while TBB loss was observed for all species except for the snapping turtle. Several metabolites were observed in all of the incubations except for snapping turtle. Metabolites observed appeared to be derived from TBB, given their structures and lack of appearance in the snapping turtle incubations. One of these metabolites, 2,3,4,5-tetrabromomethylbenzoate has been identified for the first time in a biological system. When metabolized, TBB and TBPH loss was found in each subcellular fraction suggesting that the enzyme(s) involved are present in both soluble and membrane-bound forms. It can be concluded that a broad range of species are capable of metabolizing TBB and TBPH to various metabolites and further research should be carried out to ascertain the specific products formed from metabolism of TBB and TBPH.