Tetrabromobisphenol A and hexabromocyclododecane flame retardants in infant-mother paired serum samples, and their relationships with thyroid hormones and environmental factors.

The concentrations of tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs), and their correlations with thyroid hormones, were investigated in sera from 26 infants with congenital hypothyroidism, 12 healthy infants, and their mothers. The analyte concentrations were not significantly different in the two infant groups. Polybrominated diphenyl ethers (measured in a previous study) were the dominant brominated flame retardants, contributing 42-87% of the total, and HBCDs contributed 5-18%. TBBPA concentrations were 2-5 times higher in the infants than in the mothers. The TBBPA concentrations decreased dramatically with age for 2-3 months after birth, which might be caused by its relatively high maternal transfer rate, short half-life, and fast excretion. Significant correlations were found between mothers and infants in the TBBPA and HBCD concentrations, implying that maternal transfer was important. TBBPA correlated weakly with thyroid hormones, showing a positive relationship with FT4 but a negative relationship with T3.