PBDE

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PBDE, or polybrominated diphenyl ether, is a flame-retardant sub-family of the brominated flame-retardant group. They have been used in a wide array of household products, including fabrics, furniture, and electronics. There are three main types, referred to as penta, octa and deca for the number of bromine atoms in the molecule. After studies in Sweden found substances related to PentaBDE accumulating in breast milk and other tissues, Sweden reduced the use of this substance. A follow-up study has in the meantime indicated declining levels.[1]

The European Union has carried out a comprehensive risk assessment under the Existing Substances Regulation 793/93/EEC of Penta-, Octa- and DecaBDE. As a consequence the EU has banned the use of Penta-and OctaBDE since 2004. Deca use has been restricted under the European Union's RoHS Directive.

Surprisingly, an experiment done the at Woods Hole Oceanographic Institution in Massachusetts in 2005 showed that the isotopic signature of PBDEs found in whale blubber contained carbon-14, the naturally occurring radioactive isotope of carbon. If the PBDEs in the whale had come from artificial (human-made) sources, they would have only contained carbon-12 and no carbon-14 due to the fact that virtually all PBDEs which are produced artificially use petroleum as the source of carbon, all carbon-14 would have long since completely decayed from that source.[2] The experiment thus shows that there must be some as yet unidentified natural source of PBDEs. However this source is extremely unlikely to account for the concentrations of PBDEs measured in human tissues, wildlife, household dust and common foods.

Contents

[edit] Sub-groups

Chemical structure of PBDEs
Chemical structure of PBDEs

The family of PBDEs consists of 209 different substances, which are called congeners (PBDE = C12H10-xBrxO (x = 1-10 = m + n)).

There are two sub-groups:

Lower brominated PBDEs have 1-5 bromine atoms and are regarded as the most dangerous ones, because they are smaller molecules which can be absorbed by living organisms. Lower brominated PBDEs have been known to affect hormone levels in the thyroid gland. Studies have linked them to reproductive and neurological risks at certain concentrations or higher.[3]

Higher brominated PBDEs have more than 5 bromine atoms and were formerly regarded as environmentally harmless chemical compounds, but studies by the Swedish Environmental Board have linked them to thin egg shells for Peregrine falcons.[4]

[edit] Health concerns

Since 1998, there have been concerns raised about the safety of PBDEs after Swedish scientists noticed substances related to PentaBDE to be accumulating in human breast milk.[5] Based on a comprehensive risk assessment under the Existing Substances Regulation 793/93/EEC, the EU has banned the use of Penta- and OctaBDE since 2004.[6]

Some studies in Canada have found notable concentrations of PBDEs in common food products such as salmon, ground beef, butter, and cheese.[7] In Canada there is no set limit for what upper amount of PBDEs in the human body is still considered to be safe, but there remains concern in the general public that the PBDEs are having harmful effects on human health and the environment.

Environmental organizations argue that all PBDEs should be banned as they aren’t needed and replacements are available.[citation needed] But, the electronics industry claims that PBDEs are applied to most newly manufactured electronic assemblies such as printed circuit boards and capacitors and thus are vital to their business.[citation needed]

There is growing evidence that indicates these chemicals may possess liver toxicity, thyroid toxicity, and neurodevelopmental toxicity.[3]

The brominated flame retardant industry states a belief that a chemical substance should be evaluated as to its potential impact on human health or the environment.[citation needed] If a substance poses a risk it should be regulated and if it does not pose a risk its use should not be restricted.[citation needed] All commercial PBDE products have undergone a thorough evaluation and as a result Penta- and OctaBDE were banned but no risk for DecaBDE was found and therefore there are no restrictions on this substance.[6] None of the alternative products have undergone a similarly detailed scientific evaluation.[citation needed]

[edit] References

  1. ^ Y. Lind, P. O. Darnerud, S. Atuma, M. Aune, W. Becker, R. Bjerselius, S. Cnattingius and A. Glynn (2003). "Polybrominated diphenyl ethers in breast milk from Uppsala County, Sweden." Environmental Research 93(2): 186-194. PMID 12963403
  2. ^ Emma L. Teuten, Li Xu, Christopher M. Reddy (2005): "Two Abundant Bioaccumulated Halogenated Compounds Are Natural Products". Science, 307, 5711: 917–920
  3. ^ a b Environment and Science Technology article "Rapidly rising PBDE levels in North America"
  4. ^ Lindberg, P., U. Sellström, L. Haggberg and C. A. de Wit (2004): "Higher brominated diphenyl ethers and hexabromocyclododecane found in eggs of peregrine falcons (Falco peregrinus) breeding in Sweden." Environmental Science & Technology 38(1): 93-96. PMID 14740722
  5. ^ Science News Online article "New PCBs?"
  6. ^ a b DIRECTIVE 2003/11/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL [1]
  7. ^ Globe and Mail article "Common foods laced with chemical"

[edit] External links

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