Metabolites of Organophosphate Flame Retardants and 2-Ethylhexyl Tetrabromobenzoate in Urine from Paired Mothers and Toddlers

Abstract

As a result of the polybrominated diphenyl ether (PBDE) ban in the mid-2000s, the chemical flame retardant market has moved toward alterative compounds including chlorinated alkyl and nonchlorinated aryl organophosphate flame retardants (OPFRs) as well as aromatic brominated compounds such as Firemaster 550 (FM550). Recent studies have shown that the OPFRs and Firemaster 550 components are frequently detected in polyurethane foams and in indoor dust. Some OPFRs are considered carcinogenic and/or neurodevelopmental toxicants, and children's exposure to these compounds is a concern. OPFRs are readily metabolized and excreted in the urine as their dialkyl and diaryl compounds which function as biomarkers for OPFR exposure. Limited research has shown that adults are broadly exposed to OPFRs, but nothing is known about children's exposure. Similarly, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), a FM550 component, is metabolized to tetrabromobenzoic acid (TBBA). The current study measured levels of bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(1-chloro-2-propyl) phosphate (BCIPP), diphenyl phosphate (DPHP), 2 alkylated DPHPs, and TBBA in urine collected in 2013 from 21 US mother-toddler pairs. BDCIPP, DPHP, and ip-DPHP were detected in 100%, 98%, and 96% of all individuals, whereas BCIPP and tert-butyl-DPHP (tb-DPHP) were only detected in 8% and 13%. Further, TBBA was detected in 27% of adults but 70% of children. Overall, children had higher urinary levels of BDCIPP, DPHP, ip-DPHP, and TBBA as compared to their mothers, suggesting higher exposure. For example, on average, BDCIPP levels in children were 4.9 times those of mothers. BDCIPP and DPHP levels in mother's urine were also significantly correlated with levels in children's urine, suggesting similar exposure routes, likely in the home environment. Various potential predictors of OPFR exposure were assessed using a questionnaire. In children some predictors of hand-mouth exposure were associated with elevated BDCIPP and DPHP levels (e.g., less frequent hand washing for BDCIPP). Overall, these trends are consistent with higher flame retardant levels in children as a result of increased hand-mouth behavior and elevated dust exposure.