New research has identified several anaerobic bacterial species that break down deca-PBDE into much more toxic intermediates. As the most popular brominated flame-retardant available, this news places the future of deca-PBDE at risk.
deca BDE Path To Toxicity
Science News has been reporting extensively on PBDEs since 2001. The growing body of scientific studies has documented rising levels of these compounds in human breast milk, developmental abnormalities in animals and neurological impairment in mice. Researchers in this field have concluded that PBDEs are comparable to PCBs in their toxicity, persistence, and pervasiveness.
A team of environmental engineers lead by Lisa Alvarez-Cohen was looking for ways to use bioremediation to break down PBDEs into harmless compounds. Instead, they found that naturally occurring bacteria removed some of the bromines from deca-BDE, producing much more toxic end products.
Considered the most stable of the PBDEs, deca-BDE was excluded from the RoHS ban. In general, PBDEs with fewer bromine atoms are less stable and more toxic. The penta- and octa- versions banned by RoHS are in this category.
The work done by Alvarez-Cohen’s team identified the individual bacteria and the end products they produced. Each bacterium removed a limited number of bromine atoms. Sulfurospirillum multivorans took deca-BDE down from 10 bromines to seven or eight. Dehalococcoides ethenogenes converted octa-BCE into forms with five, six or seven bromines. However, D ethenogenes did not affect deca-BDE. When the group studied mixtures of bacteria, they found BDEs with just two to four bromines, including the most toxic substances found during the study.
In nature, bacteria almost always occur in mixtures, or communities. Thus it is easy to see how soil bacteria could convert deca-BDE into toxic forms via a simple cascade. The waste of one bacterial species feeds another until many forms of BDEs, including the most toxic, are distributed throughout the soil.
Furthermore, the Science News article quotes Robert C. Hale of the Virginia Institute of Marine Science in Gloucester Point. Hale notes that fish and sunlight convert deca-BDE into other forms with lower bromine counts.
Given all this science, the concern for industry is that the EC might revise RoHS and add deca-BDE to the list of banned flame-retardants. Supporters would have a tough time making a case for keeping it. There are non-brominated alternatives available. Levels of BDEs in humans keeps rising exponentially and North Americans show levels 10-20 times as high as Europeans.
The best bet for electronics companies is to insist on parts and materials that are free of brominated flame-retardants. I suspect the EU will respond to the new research by banning deca-BDE within three years. Predicting politics is always hard, but the evidence against deca-BDE is equally hard to ignore. The path of least risk is to emulate Japanese companies and eliminate the offending compounds. The result of this choice for the Japanese has been the lowest levels of PBDEs in the blood, for any industrial nation.