Chemical Study on Brominated Flame-retardants

GENERAL Brominated flame-retardants are used for fire prevention and inhibition in polymers, rubber, textiles and wood. Flame retarded polymers are widely used in cars, consumer electronics, computers, electrical equipment and building materials. Dominant use of brominated flame-retardants in these materials is primarily based on their high specific flame retardancy and good mixing properties with polymers. Flame-retarded textiles are primarily used in upholstery of cars, trains, aircraft and other public facilities. Current world-wide demand of brominated flame-retardants is estimated at 350,000 tonnes/y with tetrabromobisphenol A (TBBPA) as the major compound (45-50% of total demand). Further a wide range of brominated compounds such as diphenylethers, biphenyls and cyclo-aliphatics are used. For the next 4 years, overall production is believed to grow at a rate of ca. 8.5% per year. SOURCES AND EMISSIONS It is estimated that in The Netherlands yearly 30,000 tonnes TBBPA and 5,000 tonnes hexabromocyclododecane (HBCD) are produced at Broomchemie in Terneuzen. Only a small fraction of these amounts, 1,700 and 400 tonnes/y respectively, are used in The Netherlands. Major other compound is decabromodiphenylether with an estimated demand of ca. 600 tonnes/y. A review of all produced and used amounts is given in table 1. At the production site in Terneuzen approximately 15 tonnes TBBPA and 0.8 tonnes HBCD are emitted to the surface water annually. Corresponding emissions to the atmosphere are estimated at 8.4 and 0.4 tonnes/y respectively. TBBPA emissions due to compounding, processing and use of brominated polymers are relatively low. HBCD emissions due to evaporation losses during service life are however, significant (11 tonnes/y; see table 1). Emissions due to the use of other compounds are relatively low. On an European scale, emissions of TBBPA and HBCD significantly increase as a result of the larger scale of compounding, processing and polymer use. For the other compounds it was assessed that only the use of tetra- and pentabromodiphenylether gives rise to emissions of 100 and 15 tonnes/y to the atmosphere (see table 1). ENVIRONMENTAL CHARACTERISTICS AND TOXICITY IN AQUATIC SYSTEMS Polybrominated biphenyls (PBBs) and diphenylethers (PBDEs), TBBPA and HBCD are characterised by low solubility in water ( 30 days). Highly brominated compounds were hardly accumulated. Corresponding BCF values for PBDEs range from 50,000 l/kg for tetrabromodiphenylether to < 30 l/kg for the decabromo compound. TBBPA and HBCD also accumulate significantly, with BCF values of 3,000 and 18,000 l/kg in fish respectively. TBBPA is however rapidly excreted on depuration (half life < 24h). From both field experiments and biodegradation tests can be concluded that PBBs are persistent under environmental conditions. Scarce biodegradation test results for PBDEs indicate a similar persistence in the environment. Laboratory evidence for photolytic debromination of PBBs and PBDEs could not be confirmed under environmental conditions. This means that the suspected conversion of non-mobile and non-accumulative compounds into the more soluble and bioaccumulative congeners is not likely to occur. Bioaccumulation studies with fish on the other hand, show that decabromodiphenylether may be slightly metabolised into hexa- to nonabromodiphenylethers. The highly bioaccumulative tetra- and penta congeners were however not identified. Biodegradation studies of TBBPA indicate that this compound is degraded slowly under environmental with half lives ranging from 50 \u96 100 days. The scarce toxicity data available indicate that the toxicity of lower brominated compounds for freshwater and marine organisms lies around the solubility limit. These brominated flame-retardants therefore may present a risk to aquatic organisms. OCCURENCE AND BEHAVIOUR IN AQUATIC SYSTEMS Significantly increased levels of PBBs and PBDEs are found in sediments near production plants and polymer processing sites, with highest levels for highly brominated compounds. Levels in water were all below the detection limit. In all aquatic biota, the lower brominated substances are the dominant compounds. Historical PBDE levels in Swedish river systems seems to indicate that the environmental release of these compounds is declining, whereas high levels in sperm whales demonstrate that lower brominated diphenylethers already have reached the deeper regions of the Atlantic Ocean. POLICY Although there has been a proposition in 1991 in the Netherlands to forbid the use of PBBs and PBDEs, this ban is still not enforced. There is an EC guideline in which PBBs are forbidden in textiles that make contact with the skin. Furthermore some PBBs and PBDEs are on the VROM list of dangerous substances, the EC first and second priority lists, the OSPAR list, the POP list and the PIC list. In the USA and Switzerland PBBs are forbidden. The industry participates in voluntary agreements (VIC) to diminish emission and waste. PROGNOSIS Although it is anticipated that halogenated flame-retardants in waste materials will be forbidden by the EC in 2004, global demand for brominated flameretardants is growing currently at an annual rate of 8.5%. This will result in a demand in 2004 of 500,000 tonnes/year, equivalent to a more than 3-fold increase relative to 1992. Within Western Europe, the commercial production of penta- and octabromodiphenylether recently has been stopped. Further it is expected that decaBB production will decline over the next years. It is not known whether also the use of these PBB and PBDE compounds has ceased or that these compounds are now supplied from outside the EU. On the other hand, the production of TBBPA and HBCD has significantly increased over the last years. These developments might indicate that compounds as PBBs and PBDEs are already substituted by other brominated products. Industry information to verify these matters was not available. CONCLUSSIONS AND RECOMMENDATIONS From the results of this study can be concluded that especially lower brominated PBBs and PBDEs are widely spread in the environment, with a preference for bioaccumulation in aquatic biota. Current data on the release and distribution of higher brominated PBBs and PBDEs are limited, but suggest that these compounds will primarily bind to sediment and hardly will spread in aquatic systems or accumulate in biota. For TBBPA and HBCD, adequate measurement data on environmental distribution are lacking. Emission distribution modelling results indicate however that TBBPA has comparable environmental properties as lower brominated PBDEs with the exception that it is slightly biodegradable and has a low excretion half life in fish. For HBCD is expected that it will bind strongly to sediment and bioaccumulate in fish. Estimates for emissions to the environment demonstrate that significant TBBPA amounts may be released to surface water by discharge of treated wastewater. Emissions to air are predominantly caused by evaporation of HBCD, tetraBDE and pentaBDE during service life. All emission estimates were based on generalised emission factors from relatively dated references. It is unknown to what extent these emission factors are representative for the current production processes and use. Due to uncertainties about the actual form in which brominated compounds are dissolved in water, it is further not known to what extent the computed emission estimates correspond with the actual emissions. For evaluation of the aquatic toxicity of selected compounds, only scarce data were available. Considering the large emission estimates for low brominated compounds to surface water and atmosphere, their high tendency to spread in aquatic systems and the fact that their toxicity for aquatic organisms lies around the solubility limit, it is recommended to perform an additional study on these compounds with emphasis on collection and verification of recent emission factors and toxicity data.Investigating for chemicals in the futur