Academic journal article Environmental Health Perspectives

Urinary Tetrabromobenzoic Acid (TBBA) as a Biomarker of Exposure to the Flame Retardant Mixture Firemaster[R] 550

Academic journal article Environmental Health Perspectives

Urinary Tetrabromobenzoic Acid (TBBA) as a Biomarker of Exposure to the Flame Retardant Mixture Firemaster[R] 550

Article excerpt

Introduction

Flame retardant (FR) chemicals are commonly applied to raw materials and consumer products to reduce their flammability and meet fire safety standards. Until recently, polybrominated diphenyl ethers (PBDEs) accounted for a large portion of FRs added to polymers and resins used in furniture, electronics, and building materials (de Wit 2002). However, concern over their persistence, bioaccumulation, and toxicity led to voluntary phaseouts and bans of several commercial PBDE mixtures from the marketplace in many countries, including the United States (Costa et al. 2008; U.S. Environmental Protection Agency 2009).

To maintain compliance with consumer product flammability standards, various PBDE replacements have been developed and introduced into commerce (Covaci et al. 2011; Stapleton et al. 2008a; van der Veen and de Boer 2012). In 2003, Chemtura introduced Firemaster[R] 550 (FM550) as a replacement for the commercial pentabrominated diphenyl ether (pentaBDE) mixture used in polyurethane foam applications (Stapleton et al. 2008a). Stapleton et al. (2008a) identified four main components of FM550: a) triphenyl phosphate (TPP); b) a mixture of isopropylated triphenyl phosphate isomers (ITPs); c) 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB); and d) bis(2-ethylhexyl)2,3,4,5-tetrabromophthalate (TBPH). These components have been frequently detected in polyurethane foam samples from consumer goods, including furniture and baby products [e.g., nursing pillows and changing-table pads (Stapleton et al. 2009, 2011)]. Based on these two studies (Stapleton et al. 2009, 2011), FM550 appears to be the second most common FR mixture applied to foam-containing products. However, with the expected phaseout of tris(1,3-dichloroisopropyl)phosphate (TDCPP), use of FM550 may increase.

Like PBDEs, FM550 is an additive FR (i.e., not chemically bound to products) and its components leach into the environment over time, as evidenced by the prevalence of TBB and TBPH in indoor dust, outdoor air, and sewage (Ali et al. 2012; Covaci et al. 2011; Dodson et al. 2012; La Guardia et al. 2010; Ma et al. 2012; Stapleton et al. 2008a, 2009). These data suggest that the general population comes into contact with FM550 frequently and widespread exposure is likely; however, potential exposure sources and routes of human exposures have yet to be investigated. Based on similarities between FM550 and PBDEs (e.g., modes of application, presence of brominated aromatic backbones), similar exposure pathways could be expected. For PBDEs, indoor dust has been identified as an important contributor to overall body burden, and data suggest that exposure via hands (e.g., incidental ingestion through hand-to-mouth contact) may in part explain how PBDEs get into the body (Johnson et al. 2010; Stapleton et al. 2012; Watkins et al. 2011).

Relatively little is known about the toxico-kinetics of FM550 components. Recent in vitro evidence, however, suggested that TBB is metabolized to 2,3,4,5-tetrabromo-benzoic acid (TBBA) in human hepatic tissues, whereas TBPH appears to be recalcitrant to metabolism (Roberts et al. 2012). The toxicities of FM550 components, as well as those of their potential metabolites (e.g., TBBA), are largely unknown because few studies have investigated the impacts of exposure. However, Patisaul et al. (2013) recently reported that FM550 is an endocrine disruptor and an obesogen; they found that pregnant rats exposed to FM550 across gestation and lactation had altered thyroid function and that their female offspring entered puberty early. In addition, offspring were 30-60% heavier by weaning, an effect that persisted into adulthood.

To our knowledge, no assessments of FM550 exposure and associated health outcomes have been carried out in human populations. Such studies rely on accurate means of assessing exposure; however, there is no biomarker of exposure to FM550, and data on environmental contributions to the body burden remain sparse. …

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