Urinary bromophenol glucuronide and sulfate conjugates: Potential human exposure molecular markers for polybrominated diphenyl ethers

One possible source of urinary bromophenol (BP) glucuronide and sulfate conjugates in mammalian animal models and humans is polybromodiphenyl ethers (PBDEs), a group of additive flame-retardants found ubiquitously in the environment. In order to study the correlation between levels of PBDEs in human blood plasma and those of the corresponding BP-conjugates in human urine, concentrations of 17 BDE congeners, 22 OH-BDE and 13 MeO-BDE metabolites, and 3 BPs in plasma collected from 100 voluntary donors in Hong Kong were measured by gas chromatograph tandem mass spectrometry (GC-MS). Geometric mean concentration of σPBDEs, σOH-BDEs, σMeO-BDEs and σBPs in human plasma were 4.45ngg^-1lw, 1.88ngg^-1lw, 0.42ngg^-1lw and 1.59ngg^-1lw respectively. Concentrations of glucuronide and sulfate conjugates of 2,4-dibromophenol (2,4-DBP) and 2,4,6-tribromophenol (2,4,6-TBP) in paired samples of urine were determined by liquid chromatography tandem triple quadrupole mass spectrometry (LC-MS/MS). BP-conjugates were found in all of the parallel urine samples, in the range of 0.08-106.49μgg^-1-creatinine. Correlations among plasma concentrations of σPBDEs/σOH-BDEs/σMeO-BDEs/σBPs and BP-conjugates in urine were evaluated by multivariate regression and Pearson product correlation analyses. These urinary BP-conjugates were positively correlated with σPBDEs in blood plasma, but were either not or negatively correlated with other organobromine compounds in blood plasma. Stronger correlations (Pearson's r as great as 0.881) were observed between concentrations of BDE congeners having the same number and pattern of bromine substitution on their phenyl rings in blood plasma and their corresponding BP-conjugates in urine.