Polybrominated Diphenyl Ethers PBDEs

Like PBBs and PCBs, this group comprises a total of 209 theoretically possible congeners (Table 1). The commercial PBDE mixtures are nominally deca-, octa-, and pentabrominated. Penta-BDE formulation consists of 41-42% tetra-BDEs (mainly BDE-47) and 44-45% penta-BDEs (predominantly BDE-99 and BDE-100), whereas deca-BDE formulation consists mainly of BDE-209 (97-98%), with a small amoimt of nona-BDES (0.3-3%) [13]. Some 67 000 tons were manufactured in 1999 [14], an amount rivalling PCBs at the height of their production. 

Of the three main technical mixtures in use, the penta-BDE and octa-BDE mixtures are currently being phased out in Europe. Consequently, a shift in production of deca-BDE mixtures for these lower brominated PBDE mixtures has taken place. A recent report of The Bromine Science Environmental Foriun (BSEF) estimated the total market demand for the major commercial BFRs in 2001 [17]. This shows the dominance of tetrabromobisphenol-A (TBBPA) (59% of total world usage) and the deca-mix PBDE formulation (27% of total world usage) in volume terms. 

Brominated bisphenol A compounds with the lowest degree of bromination showed the highest estrogenic potencies (EC50 value of 0.5 pM for 3-monobromobi-sphenol A). 

Features favoring estrogenicity of individual PBDEs include  

2) at least one para bromine atom (preferably on the same phenyl ring as the ortho bromines) 

3) non-brominated ortho-meta or meta carbons on the other phenyl ring. 

These compounds are flame retardants used in products such as flexible polyurethane foams (used in upholstery), plastic appliance housing, wire and cable insulation, and coatings at weight fractions that can range from 10 to 30%. About 67,000 

Plasticizer Symbol Chronic exposure NOAEL mg/kg body weight/day BCF 1/kg Oral toxicity  

2-Cyclohexanedicarboxylic acid, dinonyl ester DINCtf 40-200 189 Negative cancer bioassay 

Trioctyltrimellitate TOTM Not available 1-3 Negative reproductive toxicology effects 

Phthalate substitutes can also leach out of plastics, and their toxicity to human consumers has not as yet been comprehensively studied. Once the functional equivalence of a substitute plasticizer is established, exhaustive studies need to be imdertaken to unambiguously validate their safety to health and environment. 

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Costa, L.G. and Giordano, G. (2007). Developmental neurotoxicity of polybrominated diphenyl ether (PBDE) flame retardants. Neurotoxicology 28, 1047-1067. 

Sellstrom, U., Jansson, B., and Kierkegaard, C. et al. (1993). Polybrominated diphenyl ethers (PBDE) in biological samples from the Swedish environment. Chemosphere 26, 1703-1718. 

He J, KR Robrock, L Alvarez-Cohen (2006) Microbial rednctive debromination of polybrominated diphenyl ethers (PBDEs). Environ Sci Technol 40 4429-4434. 

For this purpose, the WEEE Directive has been complemented with an additional directive that limits the use of certain pollutants in these products. The EC Directive 2002/95/EC on the Restriction of the use of certain Hazardous Substances in electrical and electronic equipment (RoHS Directive) ([7], recast 2011 [9]) restricts the use of the six harmful substances/substance families lead, mercury, hexavalent chromium, polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE) to 0.1% and cadmium to 0.01% w/w per homogenous material in equipment and components, but with several exemptions for a wide range of applications (Annex III and IV). 

Table 1 Concentrations of chlorinated polycyclic aromatic hydrocarbons (CIPAHs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) in ambient air, soil, and human samples collected from e-waste recycling and reference sites in China... 

Wen S, Yang F, Li JG, Gong Y, Zhang XL, Hui Y, Wu YN, Zhao YF, Xu Y (2009) Polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) monitored by tree bark in an e-waste recycling area. Chemosphere 74(7) 981-987. doi 10.1016/j.chemosphere.2008.10.002... 

BFRs are one of the last classes of halogenated compounds that are still being produced worldwide and used in high quantities in many applications. In order to meet fire safety regulations, flame retardants (FRs) are applied to combustible materials such as polymers, plastics, wood, paper, and textiles. Approximately 25% of all FRs contain bromine as the active ingredient. More than 80 different aliphatic, cyclo-aliphatic, aromatic, and polymeric compounds are used as BFRs. BFRs, such as polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), have been used in different consumer products in large quantities, and consequently they were detected in the environment, biota, and even in human samples [26, 27]. 

Sites near industrial areas in the Ebro have been found to have the highest concentration of priority contaminants [15, 47—49], while dispersion of agricultural products by drift, runoff and drainage has resulted in residues being found in ground-waters, rivers, coastal waters and lakes far from point sources [50]. Priority contaminants in aquatic environments include persistent organic pollutants (POPs) such as dichlorodiphenylethylenes (DDT) and polybrominated diphenyl ethers (PBDEs). 

Fig. 7 Generic chemical structures of polyhalogenated compounds. X=C1, Br. (I) Polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs) (II) chlorophenols (CPs), bromophenols (BPs) (III) polychlorinated diphenyl ethers (PCDE), polybrominated diphenyl ethers (PBDE) (IV) polychlorinated dibenzo-p-dioxin (PCDD), polybrominated dibenzo-p-dioxin (PBDD) (V) polychlorinated dibenzofuran (PCDF), polybrominated dibenzofuran (PBDF) (VI) tetrabromobisphenol A (TBBPA)...

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... 

A new study by three environmental chemists in Canada is the first to measure the levels of polybrominated diphenyl ethers (PBDEs) in the environment. PBDEs are commonly used as fire retardants in plastics, and have been found by the researchers to be accumulating rapidly in animals in the Arctic. Details of the study and its unhappy findings are presented here. 

T. and Jiang, G. (2006) Quantitative structure-activity relationship for prediction of the toxicity of polybrominated diphenyl ether (PBDE) congeners. Chemosphere, 64, 515—524. 

Booij, K. Zegers, B.N. Boon, J.P. 2002, Levels of some polybrominated diphenyl ether (PBDE) flame retardants along the Dutch coast as derived from their accumulation in SPMDs and blue mussels (Mytilus edulis). Chemosphere 46 683-688. 

Cetin, B. and Odabasi, M. Measurement of Henry s law constants of seven polybrominated diphenyl ether (PBDE) congeners as a function of temperature, Atmos. Environ., 39(31) 5273-5280, 2005. 

Due to their adverse health effects, several restrictions and bans have been imposed on the usage of polybrominated diphenyl ethers (PBDEs), namely the penta-, octa-, and deca-BDE formulations, in Europe, China, North America, and Japan (http //www. bsef.com). The restricted usage of these PBDEs increased the market demand for substitute brominated flame retardants (BERs) including hexabromocyclododecanes... 

Kalantzi OI, Geens T, Covaci A, Siskos PA (2011) Distribution of polybrominated diphenyl ethers (PBDEs) and other persistent organic pollutants in human serum from Greece. Environ Int 37 349-353... 

The term brominated flame retardant (BFR) incorporates more than 175 different types of substances, which form the largest class of flame retardants other classes are phosphorus-containing, nitrogen-containing, and inorganic flame retardants (Bimbaum and Sttaskal 2004). The major BFR substances in use today (depicted in Fig. 4.6) are tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), and mixtures of polybrominated diphenyl ethers (PBDEs) (namely, deca-bromodiphenyl ether (DBDE), octabromodiphenyl ether (OBDE), and pentabro-modiphenyl ether (pentaBDE)). 

Fig. 4.6 Chemical structures of (a) tetrabromobisphenol A (TBBPA), (b) hexabromocyclodo-decane (HBCD), and (c) polybrominated diphenyl ethers (PBDEs)...

Fig. 16.19 GC-ECD chromatograms showing appearance of polybrominated diphenyl ether (PBDE) congeners, after sunlight irradiation of BDE-209 (retention time = 88.7 min) adsorbed on montmorillonite, at different times. Reprinted with permission from Ahn MY, Filley TR, Jafvert CT, Nies L, Hua I, Bezares-Cruz J (2006) Photodegradation of decabromodiphenyl ether adsorbed onto clay minerals, metal oxides, and sediment. Environ. Sci. Technol. 40 215-220. Copyright 2006. American Chemical Society...

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