In vitro endocrine disruption and TCDD-like effects of three novel brominated flame retardants: TBPH, TBB, & TBCO

• The three novel brominated flame retardants are endocrine disrupting compounds.
• TBB, TBPH, and TBCO do not activate the aryl hydrocarbon receptor in the H4IIE assay.
• TBB, TBPH and TBCO increase concentrations of E2 in the H295R steroidogenesis assay.

The novel brominated flame retardants (NBFRs), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), Bis(2-ethylhexyl)-2,3,4,5-tetrabromophtalate (TBPH), and 1,2,5,6-tetrabromocyclooctane (TBCO) are components of flame retardant mixtures including Firemaster 550 and Saytex BC-48. Despite the detection of these NBFRs in environmental and biotic matrices, studies regarding their toxicological effects are poorly represented in the literature. The present study examined endocrine disruption by these three NBFRs using the yeast YES/YAS reporter assay and the mammalian H295R steroidogenesis assay. Activation of the aryl hydrocarbon receptor (AhR) was also assessed using the H4IIE reporter assay. The NBFRs produced no TCDD-like effects in the H4IIE assay or agonistic effects in the YES/YAS assays. TBB produced a maximal antiestrogenic effect of 62% at 0.5 mg L−1 in the YES assay while TBPH and TBCO produced maximal antiandrogenic effects of 74% and 59% at 300 mg L−1 and 1500 mg L−1, respectively, in the YAS assay. Significant effects were also observed in the H295R assay. At 0.05 mg L−1, 15 mg L−1, and 15 mg L−1 TBB, TBPH, and TBCO exposures, respectively resulted in a 2.8-fold, 5.4-fold, and 3.3-fold increase in concentrations of E2. This is one of the first studies to demonstrate the in vitro endocrine disrupting potentials of TBB, TBPH, and TBCO.