Characterization of Individual Isopropylated and tert-Butylated Triarylphosphate (ITP and TBPP) Isomers in Several Commercial Flame Retardant Mixtures and House Dust Standard Reference Material SRM 2585

Abstract

Since the phase-out of pentaBDE in the early 2000s, replacement flame-retardant mixtures including Firemaster 550 (FM 550), Firemaster 600 (FM 600), and organophosphate aryl ester technical mixtures have been increasingly used to treat polyurethane foam in residential upholstered furniture. These mixtures contain isomers of isopropylated and tert-butylated triarylphosphate esters (ITPs and TBPPs), which have similar or greater neuro- and developmental toxicity compared to BDE 47 in high-throughput assays. Additionally, human exposure to ITPs and TBPPs has been demonstrated to be widespread in several recent studies; however, the relative composition of these mixtures has remained largely uncharacterized. Using available authentic standards, the present study quantified the contribution of individual ITP and TBPP isomers in four commercial flame retardant mixtures: FM 550, FM 600, an ITP mixture, and a TBPP mixture. Findings suggest similarities between FM 550 and the ITP mixture, with 2-isopropylphenyl diphenyl phosphate (2IPPDPP), 2,4-diisopropylphenyl diphenyl phosphate (24DIPPDPP), and bis(2-isopropylphenyl) phenyl phosphate (B2IPPPP) being the most prevalent ITP isomers in both mixtures. FM 600 differed from FM 550 in that it contained TBPP isomers instead of ITP isomers. These analytes were also detected and quantified in a house dust standard reference material, SRM 2585, demonstrating their environmental relevance.

Figure 1

(A) General structure of an ITP isomer. (B) General structure of a TBPP isomer. Isopropylation and tert-butylation can occur at the ortho, meta, or para position and the degree of substitution varies among isomers.

Figure 2

A comparison of the contributions of individual components in the FM 550 and ITP mixture suggests a common ITP formulation. FM 550 is shown in black, and the ITP mixture is shown in white. The two brominated components of FM 550, EH-TBB and BEH-TEBP, comprise ~43.6% of the mixture and are absent in the ITP mixture.

Figure 3

A comparison of the contributions of individual components in the FM 600 and TBPP mixture suggests a disparate TBPP formulation. FM 600 is shown in gray, and the TBPP mixture is shown in white. Strikingly, FM 600 contained relatively little TPHP and mono-substituted TBPP isomer compared to the TBPP mixture. The concentration of FM 660 in the foam was assumed to be 4% by weight.