Brominated flame retardants bioaccumulation

Keywords Bioaccumulation, Bioavailability, Brominated flame retardants, Hexabromocyclododecane, Polybrominated diphenyl ether... 

The replacement of established chemistries with newer ones is one of the classic drivers of change in the chemical industry. One of the current hotbeds of this kind of change is the replacement of brominated flame retardants in polymer formulations. The brominated flame retardants under the most scrutiny have been polybrominated diphenyl ethers, particularly penta- and octabromodiphenyl ether, which have been shown to be persistent in the environment and to bioaccumulate. Great Lakes Chemical is voluntarily phasing out penta- and octa-BDEs by the end of next year. The phaseout is made possible by the clean bill of health granted by EPA for Firemaster 550, a replacement for penta-BDE in flexible PU applications. BRG Townsend claims the phaseout of penta-BDE and octa-BDE is not as earth shattering as would be an exit from deca-BDE, a styrenics additive that is produced in the highest volume of the PBDEs. 

The Danish Environmental Protection Agency has started work to draft a national plan to control brominated flame retardants, and has published what officials claim to be the most exhaustive national survey analysing the flow of such substances and assessing possible substitutes for specific applications. The survey found that the major source of BFRs emissions in Denmark was from evaporation from products already in use, and underlines previous concerns about the possible harm due to bioaccumulation. Denmark is to join Sweden in urging international action to curb the use of brominated flame retardants. 

It is not possible to achieve "adequate control" of the risks of persistent, bioaccumulative chemicals. The fact that traditional risk assessment cannot reasonably be applied to such chemicals, and that a revised PBT (persistent, bioaccumulative, toxic) assessment is necessary, is explicitly recognised in the EU s Technical Guidance Document for risk assessment. Their intrinsic properties mean that there is a high risk of exposure at sometime during the lifecycle of the chemical or the article that contains it. Even small releases, if they are continuous, can result in significant exposures. This is why we see significant and, in some cases, escalating levels of brominated flame retardants, nonylphenols and other persistent chemicals in breast milk, umbilical cord blood and human tissue. 

Gustafsson K, Bjork M. Burreau S, et al. 1999. Bioaccumulation kinetic of brominated flame retardants (polybrominated diphenyl ethers) in blue mussels Mytilus edulis). Environ Toxicol Chem 18(6) 1218-1224. 

Law, K. HaUdorson, T. Danell, R. Stem, G. Gewurtz, S. Alaee, M. Marvin, C. Whittle, M. Tomy, G., Bioaccumulation and trophic transfer of some brominated flame retardants in a Lake Winnipeg (Canada) food web Environ. Toxicol. Chem. 2006, 25, 2177-2186. 

In response to the continuing discovery of the persistence, bioaccumulative properties, and toxicity of POPs, regional, national and international policies ban the intentional production of compounds, such as polychlorinated biphenyls (PCBs), several organochlo-rine pesticides, such as mirex and dieldrin, and the brominated flame retardants poly-brominated diphenyl ethers (penta-BDE and octa-BDE, and most recently, deca-BDE). Policies and programs have also targeted the unintentional production and release of POPs such as polychlorinated dibenzodioxins and furans (PCDD/Fs). Evidence of the success of these policies has been seen in immediate reductions of air concentrations, followed by declining concentrations in water bodies, soils, biota and our food supplies... 

Brominated flame retardants are widely used as polymer additives in plastics, electric appliances, and textile and polyurethane foams. Some of the technical flame retardant products contain brominated organic compounds, including polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers. These compounds are structurally similar to PCBs and, therefore, their chemical properties, persistence, bioaccumulation, and distribution in the environment follow similar patterns. Moreover, they have potential endocrine disrupting properties and there are concerns over their exposure health effects. 

Many brominated flame retardants (BFRs) are persistent and bioaccumulative chemicals that are now present throughout the environment. Polybrominated diphenyl ethers (PBDEs) are one of the most common groups of BFRs and have been used to fireproof a wide variety of materials, including textiles. Some PBDEs are capable of interfering with the hormone systems involved in growth and sexual development. Under EU law, the use of some types... 

The Bromine Industry in particular, points out that non-brominated chemical flame retardants may be very hazardous and that the phase-out of BFRs may not be safe. The non-brominated alternatives listed in the above case studies are likely to be safer if they exhibit less persistence and bioaccumulation in living systems, but some do possess significant toxicity. In the last few years, some agencies have therefore investigated the relative merits of alternatives to BFRs. 

During the last decade, environmentalists have fought strongly to ban the use of brominated fire retardants, and already a number of plastics processors have voluntarily switched to non-halogenated ones (such as phosphate esters, aluminium trihydride and magnesium hydroxide fire retardants). Still, there are two contradictory forces in the fire retardant industry, one is the constant push for stronger fire-safety standards, and the other is the move to eliminate flame-retardants seen as persistent, bioaccumulative or toxic [19]. 

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