TBBPA disposition and kinetics in pregnant and nursing Wistar Han IGS rats

Tetrabromobisphenol-A (TBBPA) is a brominated flame retardant (BFR) commonly used in electronics to meet fire safety standards and has the largest worldwide production of any BFR. TBBPA has been detected in human breast milk and maternal/cord serum, indicating exposure to mothers, fetuses, and breastfeeding newborns although exposure to fetuses and newborns is poorly understood. Pregnant or nursing Wistar Han IGS rats were administered [¹⁴C]-TBBPA in a single dose (25 mg/kg, 2.5 microCi/kg) and euthanized between 0.5&24 h post dose to determine disposition in pregnant and nursing rats and their pups. Systemic exposure was largely unchanged between 1&8 h post dose in pregnant rats; [¹⁴C]-radioactivity in blood varied only slightly between 0.5&8 h (2.6 ± 0.6 → 2.6 ± 0.8 nmol-eq/mL) but was below the limit of detection at 24 h with an absorption half-life of 16min and elimination half-life of 17 h. C_max was observed at 30min in lactating rats and concentrations fell steadily through 8 h. Plasma from pregnant rats contained a mixture of TBBPA and TBBPA-conjugates at 30min but only metabolites in subsequent samples. TBBPA was not detected in lactating dam plasma in this study. Placental concentrations increased through 8 h while whole-fetus C_max occurred at 2 h post dose. In lactating animals, liver, uterus, and mammary time-concentration curves lagged slightly behind blood-concentration curves. It was clear from these studies that TBBPA is available to both the developing fetus and nursing pup following maternal exposure, and nursing pups are continuously exposed via contaminated milk produced by their mother. This research was supported in part by the Intramural Research Program of NIH/NCI.