Polybrominated dibenzofuran

H. Thoma, G. Hauschulz, E. Knorr and O. Hutzinger, "Polybrominated Dibenzofurans (PBDF) and Dibenzodioxins (PBDD) from the Pyrolysis of Neat Brominated Diphenylethers, Biphenyls and Plastic Mixtures of these Compounds,"Chemosphere, JJi, 277(1987). 

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)...

Pyrolysis of FireMaster BP-6 in the temperature range of 600 900 °C in the absence of oxygen produced bromobenzenes and brominated biphenyls as key products, but no brominated dioxins and dibenzofurans (Thoma and Hutzinger 1987 Thoma et al. 1987). Thermolysis of Hi re Mast a- BP-6 between 400 and 600 °C in the presence of air produced 23,7,8-tetrabromodibenzofuran in the percent ( 1 %10 g/kg) range (Rappe and Buser 1980). Pyrolysis of FireMaster BP-6 in an open quartz tube at 800 °C produced 0.48 1.49 gZkg2,3,7,8-TCDD equivalent levels of polybrominated dibenzofurans (Zacharewski et al. 

When pyrolysed up to 900 °C, PBDEs release polybrominated dibenzofurans (PBDEs) and... 

Approximately 11.8 million pounds of hexabromobiphenyl were used in commercial and consumer products in the United States, most in the production of plastic products with an estimated use life of 5 10 years (Neufeld et al. 1977). Since the cessation of production, all of these products, such as TV cabinet and business machine housings, must have been disposed ofby land filling or incineration (Neufeld et al. 1977). The formation of polybrominated dioxins (PBDDs) and polybrominated dibenzofurans (PBDFs) during the incineration of plastics containing PBBs remains a distinct possibility (Luijk and Covers 1992 O Keefe 1978). 

Thoma H, Hauschulz G, Knorr E, et al. 1987. Polybrominated dibenzofurans (PBDF) and... 

The cellular slime mold Dictyostelium purpureum K1001 contains AB0022A (2255), a novel antibacterial dibenzofuran, the structure of which was confirmed by total synthesis (2038). The lichen Lecanora cinereocarnea has yielded several new dibenzofurans, including three chlorinated analogues (2256-2258) (2039), and Lecanora iseana contains 2259 and 2260 (2040). The first naturally occurring polybrominated dibenzofuran, corallinafuran (2261), is present in a crustose coralline red alga that also contains corallinaether (1913) cited earlier (1769). 

Buser HR (1986), Environ. Sci. Technol. 20, 404-408.. .Polybrominated dibenzofurans and dibenzo-p-dioxins thermal reaction products of polybrominated diphenyl ether flame retardants"... 

Hamm S, Theisen J (1992), Posterbeitrag bei DIOXIN 92, Tampere, Finnland.. .Formation of polybrominated dibenzofurans and dibenzo-p-dioxins at fires of electrical appliances"... 

Hamm S, Theisen J (1992), Posterbeitrag auf dem Kongress DIOXIN 92.. .Formation of polybrominated dibenzofurans and polybrominated dibenzo-p-dioxins at fires of electrical appliances" Marklund S, Kjeller LO, Hansson M, Tysklind M, Rappe C, Ryan C, Collazo H, Dougherty R (1986), in Chlorinated Dioxins and Dibenzofurans in Perspective Determination of PCDDs and PCDFs in incineration samples and pyrolytic products", p. 79-92, Lewis Publishers, London... 

Like other organohalogen compounds such as PCBs and DDT, PBBs and PBDEs are lipophilic, and persistent [2,3]. The high resistance towards acids, bases, heat, light, reduction and oxidation is disadvantageous when these compounds are discharged into the environment, where they persist for a long time. In addition, toxic compounds, polybrominated dibenzofurans (PBDFs) and dibenzodioxins (PBDDs), may be formed when these flame retardants are heated [5]. 

UBA (Federal Environmental Agency)(1989) [Stat of facts. Polybrominated dibenzodioxins (PBDD) - Polybrominated dibenzofurans (PBDF). Second supplement Polybrominated biphenyls.] In Polybrominated dibenzodioxins and dibenzofurans (PBDD/ PBDF) from brominated flame retardants. Report of the working group on brominated flame retardants to the Environment Minister Conference. Bonn, Tederal Ministry for the Environment, Nature Conservation and Nuclear Safety, pp 95-97 (in German)... 

Health issues can be related not only to the pyrolysis products of the polymer itself, but also may be related to the compounds that come from the polymer additives. For example, in a study of pyrolysis of high impact polystyrene with decabromodiphenyi ether/antimony oxide added as a flame retardant, it has been shown that toxic polybrominated dibenzofuranes are generated during thermal decomposition in the range of 350-400° C [15]. 

Highly brominated biphenyls and diphenyl ethers have been manufactured as flame-retardants, and the diphenyl ethers have apparently become environmental contaminants (references in Sellstrom et al. 1998 see also Chapter 3, Section 3.6.3). One of the reasons for concern is the formation of polybrominated dibenzofurans and dibenzo[-l,4]-dioxins (although not 2,3,7,8-tetra-bromdibenzo[-l,4]-dioxin) during subsequent incineration (Buser 1986). Mixed cultures of organisms isolated from sediments contaminated with PCBs and PBBs were shown to debrominate PBBs under anaerobic conditions (Morris et al. 1992), and the dominant congener — 2,4,5,2,4, 5 -hexabro-mobiphenyl — could be successively debrominated to 2,2,-dibromobiphenyl. On the other hand, in sediments from the most heavily contaminated site containing contaminants in addition to PBBs, very little debromination occurred and the recalcitrance was attributed to the toxicity of the other contaminants (Morris et al. 1993). 

Analytes CB, chlorobenzenes DDE, l,l-dichloro-2,3-bis(4-chlorophenyl)ethane DDT, l,l-dichloro-2,3-bis(4-chlorophenyl)ethylene DBF, decabromobiphenyls HBCD, Hexabromo-cyclododecane HpBB, heptabromobiphenyl PBB, polybrominated biphenyl PBCCH, pentabromochlorocyclohexane PBDE, polybrominated diphenyl ether PBT, Polybutylene terephthalate PCB, Polychlorinated biphenyl PBDD, polybrominated dibenzo-/ -dioxins PBDF, polybrominated dibenzofuranes PCN, polychlorinated naphthalenes PCP, polychlorinated phenols PBB, polybrominated biphenyl PeBDE, pentabromodiphenyl ether PET, Polyethylene terephthalate PXDDs, polyhalogenated dibenzo-p-dioxins PXDFs, polyhalogenated dibenzofurans TBBPA, tetrabromobisphenol A TBPA, tetrabromophthalic anhydride TCBPA, tetrachlorobisphenol A TDBPP, tris(2,3-dibromopropyl)phosphate. 

First of all, halogen-based fire retardant additives (especially bromin-ated compounds associated with the antimony trioxide) are widely used. These systems release obscuring, corrosive and toxic smoke when they perform their fire retardant action. More, some of them release super toxic compoimds ( dioxins and polybrominated dibenzofurans) when exposed to heat during manufacturing or in fire. A continuous trend is the development of polymeric materials with reduced fire hazard, in order to meet the requirement of the international regulations (5th OECD Draft Status report (04/1993) and UN Environmental Program 1st Draft Report (01/1993)). 

Figure 1. Schematic of reaction pathways to the production of polybrominated dibenzofurans and polybrominated dibenzodioxins from polybrominated diphenylethers (a common family of flame retardants for polymers). Note x+y can equal 5, 8, or 10 implying penta-, octa- or deca-substitu-tion.

The International Program for Chemical Safety (IPCS) of the World Health Organization has made several recormnendations. Polybrominated diphenyls production (France) and use should be limited because of the concern over high persistency, bioaccumulation and potential adverse effects at low levels. There is limited toxicity data on deca- and octabromodiphenyls. Commercial use should cease unless safety is demonstrated. For the polybrominated diphenyl oxides, a Task Group felt that polybrominated dibenzofurans, and to a lesser extent the dioxins, may be formed. For decabromodiphenyl oxide, appropriate industrial hygiene measures need to be taken and environmental exposure minimized by emission control. Controlled incineration procedures should be instituted. For octabromodiphenyl oxide, the hexa- and lower isomers should be minimized. There is considerable concern over persistence in the environment and the accumulation in organisms, especially, for pentabromodiphenyl oxide. 

The HO -initiated oxidation of 2,4,4 -tribromodiphenyl ether (BDE-28) in the atmosphere and in water solution has been studied and found to occur more readily in the former, especially at the less-brominated Ph ring. The hydrox-ylated dibrominated diphenyl ethers (HO -PBDEs, PBDE = polybrominated diphenyl ethers) are formed through direct bromine-substitution reactions or secondary reactions of HO adducts. Polybrominated dibenzo-p-dioxins resulting from o-HO -PBDEs are favoured products compared with polybrominated dibenzofurans generated by bromophenols and their radicals. The complete degradation of HO adducts in the presence of O2/NO, which generates unsaturated ketones and aldehydes, is less feasible compared with the H-abstraction pathways by 03." ... 

PBDF Polybrominated dibenzofurans St, StAc Stearate, stearic acid... 

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