PBDEs properties

HBCD is a brominated aliphatic cyclic hydrocarbon used as a flame retardant in thermal insulation building materials, upholstery textiles, and electronics. In 2001, the world market demand for HBCD was 16,700 tons, from which 9,500 tons was sold in the EU. These figures make HBCD the second highest volume BFR used in Europe [29], HBCD may be used as an alternative for PBDEs in some applications. To date, there are no restrictions on the production or use of HBCD. As a result of their widespread use and their physical and chemical properties, HBCD are now ubiquitous contaminants in the environment and humans [30, 31]. 

PolyCy-benzyl L-glutamate) (PBLG), 15 109 Poly(y-ketosulfide)s, optically active, 23 711 Poly(P-alanine), 1 292 Poly-P-hydroxybutyrate (PHB), 12 482 Polybetaines, 20 479-482 applications of, 20 482 preparation of, 20 480-481 solution properties of, 20 481-482 synthesis of, 20 479-481 Polyborates, 4 256-258 Polyborosiloxanes, in silicon carbide manufacture and processing, 22 533 Polybrominated diphenyl ethers (PBDEs), 13 142-143 20 56... 

These experts collectively have knowledge of PBBs and PBDEs physical and chemical properties, toxicokinetics, key health end points, mechanisms of action, human and animal exposure, and quantification of risk to humans. All reviewers were selected in conformity with the conditions for peer review specified in Section 104(I)( 13) of the Comprehensive Environmental Response, Compensation, and Liability Act, as amended. 

However, due to the ether linkage and position/number of bromine atoms, there are important three-dimensional differences in the structures of PBBs and PBDEs that can influence the molecules receptor interactions and toxicological properties as discussed in Section 3.5, Mechanisms of Action. 

The assumption that PBBs and PBDEs share many toxicological characteristics with PCBs also does not consider geometrical differences due to the higher atomic weight and considerably larger molecular volume of bromine compare to chlorine (Hardy 2000, 2002). These differences contribute to dissimilar physical/chemical properties that can influence the relative toxicokinetics and toxicities of the chemicals. 

In other words, introduction of ortho substitutions into PBDEs or PCDEs does not create a spatial impediment for the two phenyl rings to assume a semi-flat position respect to each other as it does for PCBs or PBBs. This has implications not only for dioxin-type toxicities, but also for nondioxin-type toxicities. For example, studies have shown that mono- and diortho-substituted PCBs exhibit neurotoxic properties and structure-activity relationships for various neurological end points have been established (see Agency for Toxic Substances and Disease Registry 2000 for details). Although structure-activity relationships have not yet been fully examined for PBBs or PBDEs, it is reasonable to speculate that mono-and diortho-substituted PBDEs may not necessarily follow the neurotoxic potency rankings constructed with mono- and diortho-substituted PCBs. 

The enzyme induction properties of PBDEs have been less studied than for other structurally similar chemicals, but the existing information suggests that they can be classified as mixed-type inducers of hepatic microsomal monooxygenases (Damerud et al. 2001 de Wit 2002 Hardy 2002b). Few studies have examined the structure-induction relationships for PBDEs. Chen et al. (2001) examined the ability of 12 PBDE congeners and 3 commercial mixtures to induce EROD activity in chick and rat hepatocytes, in liver cell lines from rainbow trout, rat, and human, and in a human intestinal cell line. The number of... 

Polybrominated Diphenyl Ethers. Information found in the literature regarding the physical and chemical properties of selected technical PBDE mixtures is presented in Table 4-6. 

Table 4-6. Physical and Chemical Properties of Technical PBDE Mixtures...

Polybrominated Diphenyl Ethers. Many of the relevant physical and chemical properties of the PBDEs are not available (see Table 4-4). Very limited data are available on the physical and chemical properties for the individual congeners. Important data, such as vapor pressure, and Henry s law constant, are necessary for the prediction of the environmental fate and transport ofPBDEs. 

Hardy ML. 2002a. A comparison of the properties of the major commercial PBDPO/PBDE product to those of major PBB and PCB products. Chemosphere 45(5) 717-728. 

Semi-volatile organohalogen compounds, such as PBDEs, exist in the atmosphere in the gas-phase or associated with the particle-phase. The partitioning of compounds between these atmospheric phases is an important factor in their subsequent fate, transport, degradation, and human exposure assessment. Particle-to-gas partitioning is controlled largely by the physical properties of a compound, such as its vapor pressure and by the prevailing environmental conditions, such as the atmospheric temperature. As noted above, in the Strandberg et al. study, the samples were selected from days when the atmospheric temperature was 20 3 °C [42], At this temperature, the PBDEs were present in both the particle- and gas-phases, except for BDE-209, which was present only in the particle-phase. 

In addition to OCs, PBDEs, the popular brominated flame retardants, are now a worldwide problem even in remote areas, and Asia-Pacific region is surely no exception (Ikonomou et al., 2002 Birnbaum and Staskal, 2004 Ueno et al., 2004). PBDEs are structurally similar to PCBs and DDT and, therefore, their chemical properties, persistence and distribution in the environment follow similar patterns. Studies on the environmental behavior of PBDEs are chiefly derived from Europe, North America and the Arctic. Despite the usage of vast amounts of these compounds in Asia-Pacific region, there is a paucity of data on the prevalence of PBDEs in Asian environment. Studies are necessary to identify Asian sources of PBDEs as well as to quantify emissions and document their potential environmental fate in this region. 

PBDEs are a class of chemicals widely used as flame retardants in a variety of applications. They are ubiquitous in the environment and have been detected in various environmental media including air [76, 77], water [78], biota [1, 79], soil [80], sediments [81, 82], house dust [83,84], cars [85], humans [86] and sewage sludge [87]. PBDEs are similar in molecular structure to several well-known POPs such as PCBs and dioxins/furans. They have very similar physicochemical properties and, like these compounds, PBDEs are of environmental concern because of their high lipophilicity, persistence and resistance to degradation [88-90]. 

From their high n-octanol/water partition coefficient (K, ) (see Table 15) it can be assumed that PBDEs could be bio concentrated to a high extent in fish and other aquatic organisms. Recently the analysis, environmental fate, toxicokinetics, biotransformation, bio accumulation, toxicity, and environmental occurrence was reviewed by Pijnenburg et al. [249]. In the following part the bioconcentration of PBDEs in aquatic organisms, especially fish, is critically reviewed. Some information on endocrine disrupting properties of PBDEs is also presented. 

In this chapter the chemical and physical properties, production and use, analytical methods, environmental fate and occurrence and the toxicology of PBBs and PBDEs, are discussed. 

In a study of 78 TV sets and 34 personal computers, 78% of the modified polystyrene housings contained PBDEs, 16% PBBs, and 3% l,2-bis-(tribromo-phenoxy)ethane. Composed samples of this material with PBDEs and PBBs as flame retardants already contained traces of PBDFs and PBDDs. When PBBs were used as flame retardant, the levels of these impurities increased during the recycling process. The formation of these PBDFs and PBDDs from the primary flame retardants, should also be considered when assessing the toxic properties of PBBs and PBDEs [25]. 

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