Mammalian toxicology and human exposures to the flame retardant 2,2′,6,6′-tetrabromo-4,4′-isopropylidenediphenol (TBBPA): implications for risk assessment

Thomas Colnot, Sam Kacew, Wolfgang Dekant

The compound 2,2',6,6'-Tetrabromo-4,4'-isopropylidenediphenol (tetrabromobisphenol A, TBBPA) is used as a reactive and additive flame retardant. This review evaluates the mammalian toxicology of TBBPA and summarizes recent human exposure and risk assessments. TBBPA has a low potential for systemic or reproductive toxicity, and no-observed-adverse-effect-levels were greater than 1,000 mg/kg body weight (bw)/day in a 90-day oral toxicity study, a developmental toxicity study and a two-generation reproductive and developmental toxicity study. Some interactions of TBBPA with hormone-mediated pathways were noted in vitro; however, when studied in vivo, TBBPA did not produce adverse effects that might be considered to be related to disturbances in the endocrine system. Therefore, in accordance with internationally accepted definitions, TBBPA should not be considered an "endocrine disruptor." Furthermore, TBBPA is rapidly excreted in mammals and therefore does not have a potential for bioaccumulation. Measured concentrations of TBBPA in house dust, human diet and human serum samples are very low. Daily intakes of TBBPA in humans were estimated to not exceed a few ng/kg bw/day. Due to the low exposures and the low potential for toxicity, margins of exposures for TBBPA in the human population were between 6 × 10(4) (infants) to 6 × 10(7) (adults). Exposures of the general population are also well below the derived-no-effect-levels derived for endpoints of potential concern in REACH.