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Transport and fate of polybrominated diphenyl ethers in the Baltic and Arctic regions

image of Transport and fate of polybrominated diphenyl ethers in the Baltic and Arctic regions

In the last decades, concern has been raised regarding the use of polybrominated diphenyl ethers (PBDEs) due to its increased environmental occurrence and its possible toxicological impact in humans and wildlife. As a result, two of the commercial PBDE products have recently been banned within the EU, while the use of the third product (DecaBDE) is still approved. A dynamic, fugacity-based, regional multimedia fate and transport model (POPCYCLING-Baltic) has been used to assess the historical behaviour and the potential future fate of polybrominated diphenyl ethers (PBDEs), exemplifying different emission scenarios following the introduction of restricting measures. The past, current and future consumption and emission of PBDEs were estimated, and the environmental fate of individual compounds was modelled. The possible impact on the Arctic region is also discussed. Uncertainties in the estimates and data gaps were identified.

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Physical-chemical properties of PBDEs

Theoretically, there are 10 different homologues of PBDEs and 209 possible PBDE congeners, following the same numbering system as the PCBs. A homologue refers to a subset of the mixture having the same number of bromines, whereas a congener is further identified by the exact location of bromine(s) on the PBDE molecule. The production of PBDEs is similar to the production of PCBs, involving the bromination of diphenyl ethers in the presence of a catalyst. The bromination of diphenyl ether is reported as a fairly specific process, and substitution of bromine is likely to occur first in the 4- positions, next in the 2-positions (Rahman et al. 2001 and references therein). For this reason, all technical mixtures include a number of PBDE congeners of various degree of bromination, but the PBDE mixtures generally contain fewer congeners as compared to commercial PCB mixtures (Hooper and McDonald, 2000). The commercial mixtures that are produced today are pentaBDE, octaBDE and decaBDE. These commercial mixtures mainly contain various congeners with four or more bromines, i.e. tetra- to deca-substituted congeners, but also trace amounts of trisubstituted diphenyl ethers. Previously, unknown amounts of a lighter mixture were also produced, called tetraBDE (WHO, 1994). The composition of the commercial penta product Bromkal 70-5DE has been analysed by Sjödin et al. (1998). Additional studies of octa- and deca-mixtures have been performed by e.g. Sondack et al. (1994) and Gesellschaft für Arbeitsplatz und Umweltanalytik mbH in Germany (see referenceswithin ECB, 2002a). The composition of technical PBDE mixtures with respect to their homologue content is given in Table 4.1.

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