Does a key PBDE break down in the environment? Over the past few years, the issue of whether Deca BDE, the only PBDE flame retardant currently used in North America, breaks down in the environment has become a key issue to scientists researching the controversial compound. Klaus Rothenbacher, a toxicologist with the Bromine Science and Environmental Forum, an industry group, reignited the debate at the Fifth International Workshop on Brominated Flame Retardants (BFR 2008) held June 3-4 in Victoria, British Columbia (Canada). In his conference presentation, Rothenbacher contended that although scientists can “force” Deca BDE to debrominate in the laboratory, it is unlikely to happen in the environment. Deca BDE’s susceptibility to environmental degradation has been a concern since 2004, when two other PBDE formulations, known as Penta BDE and Octa BDE, were banned in Europe and discontinued in the U.S. because of their persistence, toxicity, and tendency to bioaccumulate. An EU ban on Deca BDE’s use began on July 1, and it has also been banned in some U.S. states. If the BDE-209 molecules that make up the majority of the Deca BDE formulation are conclusively shown to debrominate in the environment to produce the lighterweight PBDE compounds, or congeners, associated with these discontinued formulations, the finding would increase pressure to end Deca BDE’s use in North America. Toxicology research has linked PBDEs to liver and thyroid toxicity and to learning, behavior, and memory problems. “In environmentally relevant settings, there are no indications
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for significant [Deca BDE] degradation,” according to Rothenbacher’s presentation, which focused on six recent studies. The authors of two of these studies, Heather Stapleton of Duke University’s Nicholas School of the Environment and Earth Sciences and Mark La Guardia of the Virginia Institute of Marine Sciences, disagree. Rothenbacher’s presentation acknowledges a recent laboratory-based abiotic study that uses a cosolvent-enhanced biomimetic system. That study, conducted by a team led by John Tokarz of Purdue University, shows that BDE-209 can break down to produce many lighterweight PBDE congeners, including three highly accumulative PBDEs associated with Penta BDE: BDE47, BDE-99, and BDE-153. However, Rothenbacher stressed that the study’s reaction mechanism was different from what would be found in environmental sediments and that the amount of lower-brominated congeners produced was “negligible.” La Guardia agrees that many studies that use environmental samples, such as sediments from streams that receive BDE-209laden wastewater and sewage sludge, do not show that Deca BDE is disintegrating into compounds associated with Penta BDE or Octa BDE. However, he notes that both he and Stapleton have detected in environmental samples what he calls “oddball congeners,” such as BDE-179, BDE-184, and BDE-202, which contain seven or eight bromine atoms; these congeners are not found in any commercial mixture. In fact, Stapleton says that many studies now demonstrate significant formation of the so-called
2008 American Chemical Society
Published on Web 07/22/2008
oddball congeners under environmentally relevant conditions. Stapleton points to a study published in ES&T this year by researchers at the Swiss Federal Laboratories for Materials Testing and Research and the Swiss Federal Institute of Aquatic Science and Technology, which documents the presence of these oddball congeners in sediment cores. LaGuardia says that his colleague Da Chen has detected these oddball congeners in U.S. peregrine falcons, too. In May, Jeff Gearhart of the Ecology Center, a nonprofit environmental group, presented additional evidence that the Deca BDE formulation was breaking down. His newest work, which involved placing sealed quartz cuvettes containing Deca BDE inside cars, documented that Deca BDE decomposed to Tetra, Penta, Hexa, Hepta, and Octa BDEs and up to 63% of the bromine present at the beginning of the experiment was not detectable as a PBDE compound at the end of the experiment. Gearhart, Stapleton, and La Guardia agree that more research is needed to investigate the presence and toxicity of these compounds and other likely breakdown productssincluding oddball congenerssin environmental samples. —KELLYN BETTS
Note Added after ASAP Publication The version published on the Web July 22, 2008 contained a graphic that was removed from the final version published September 11, 2008.
September 15, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 6781
