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Polybrominated diphenyl ethers or PBDE, are organic compounds that are used as a flame retardant. Like other brominated flame retardants, PBDEs have been used in a wide array of products, including building materials, electronics, furnishings, motor vehicles, plastics, polyurethane foams, and textiles. They are structurally akin to the PCB’s, consisting of two halogenated aromatic rings linked by an ether group. PBDEs are classified according to the average number of bromine atoms in the molecule. The health hazards of these chemicals have attracted increasing scrutiny.

Classes of PBDEs

Chemical structure of PBDEs

The family of PBDEs consists of 209 possible substances, which are called congeners (PBDE = C₁₂H_10−xBr_xO (x = 1, 2, ..., 10 = m + n)). Congeners include dibromodiphenyl ether, tribromodiphenyl ether, tetrabromodiphenyl ether, pentabromodiphenyl ether, hexabromodiphenyl ether, heptabromodiphenyl ether, octabromodiphenyl ether, nonabromodiphenyl ether, and decabromodiphenyl ether. In the United States, PBDEs are marketed with trade names: DE-60F, DE-61, DE-62, and DE-71 applied to pentaBDE mixtures; DE-79 applied to octaBDE mixtures; DE 83R and Saytex 102E applied to decaBDE mixtures. The available commercial PBDE products are not single compounds or even single congeners but rather are composed of a mixture of congeners.

Lower brominated PBDEs

These species average 1-5 bromine atoms per molecule and are regarded as more dangerous because they more efficiently bioaccumulate. 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.¹

Higher brominated PBDEs

These species average more than 5 bromine atoms per molecule.

The commercial mixture, named pentabromodiphenyl ether, contains the pentabromo derivative predominantly (50-62%), however the mixture also contains tetrabromides (24-38%) and hexabromides (4-8%), as well as traces of the tribromides (0-1%). Similarly, commercial octabromodiphenyl ether is a mixture of homologs: hexa-, hepta-, octa-, nona-, and decabromides.

Health concerns

Since the 1990s scientists have questioned the safety of PBDEs. People are exposed to low-levels of PBDEs through ingestion of food and by inhalation. PBDEs bioaccumulate in blood, breast milk, and fat tissues. Personnel associated with the manufacture of PBDE-containing products are exposed to highest levels of PBDEs. Bioaccumulation is of particular concern in such instances, especially for personnel in recycling and repair plants of PBDE-containing products. People are also exposed to these chemicals in domestic environment because of their prevalence in common household items. Studies in Canada have found significant concentrations of PBDEs in common foods such as salmon, ground beef, butter, and cheese.² PBDEs have also been found at high levels in indoor dust, sewage sludge, and effluents from wastewater treatment plants.

Case studies

Studies show that children in the United States, Norway, Australia, and the Faroe Islands have higher levels of PBDEs than adults.³ In the United States, children's blood concentrations average 62 parts per billion (ppb) and range from 24 to 114 ppb. Published studies express concern because exposure to PBDEs impairs development of nervous system. PDBEs has also been shown to have hormone disrupting effects, particularly on estrogen and thyroid hormones. The U.S. Environmental Protection Agency (EPA) noted that PBDEs are particularly toxic to the developing brains of animals. Peer-reviewed studies have shown that even single dose administered to mice during development of the brain can cause permanent changes to behavior, including hyperactivity.⁴

Swedish scientists first reported substances related to PentaBDE were accumulating in human breast milk.⁵ Studies by the Swedish Environmental Board have linked higher brominated PBDEs to thin egg shells for Peregrine falcons.⁶ Two forms of PBDEs exist: Penta and Octa; neither are manufactured anymore in the U.S. because of health and safety concerns. Based on a comprehensive risk assessment under the Existing Substances Regulation 793/93/EEC, the EU has completely banned the use of Penta and Octa BDE since 2004.⁷. However, both chemicals are still found in furniture and foam items made before the phase-out was completed. The most-common PBDEs that are used in electronics are in a form known as Deca. Deca is banned in Europe and in some U.S. states. For PBDE, EPA has set reference dose of 7 micrograms per kilogram of body weight, which is "believed to be without appreciable effects". However, Linda Birnbaum, PhD, a senior toxicologist with the EPA notes concern: "What I see is another piece of evidence that supports the fact that levels of these chemicals in children appear to be higher than the levels in their parents; I think this study raises a red flag.⁸ Previous study by EWG in 2003 published test results showing that the average level of fire-retardants in breast milk from 20 American mothers was 75 times higher than the average levels measured in Europe.⁹

It has been postulated that increasing levels of PBDEs in the environment could be correlated with the increasing incidence of feline hyperthyroidism. However, a study in 2007 found that no association could be detected between hyperthyroid cats and serum PBDE levels.¹⁰

An experiment conducted at Woods Hole Oceanographic Institution in 2005 showed that the isotopic signature of methoxy-PBDEs found in whale blubber contained carbon-14, the naturally occurring radioactive isotope of carbon. Methoxy-PBDEs are produced by some marine species.¹¹ If the methoxy-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.¹² The isotopic signatures of the PBDEs themselves were not evaluated.

Regulations of PBDEs

As of June 1, 2006 the State of California began prohibiting the manufacture, distribution, and processing of flame retardant products containing pentabrominated diphenyl ether (pentaBDE) and octabrominated diphenyl (octaBDE). PBDEs are ubiquitous in the environment and according to the EPA exposure may pose health risks. According to U.S.EPA's Integrated Risk Information System evidence that indicates PBDEs may possess liver toxicity, thyroid toxicity, and neurodevelopmental toxicity.¹³¹⁴ In June 2008 EPA set a safe daily exposure level ranging from 0.1 to 7 ug per kg body weight per day for 4 most common PBDEs.¹⁵ In April 2007, the legislature of the state of Washington passed a bill banning the use of PBDEs.¹⁶ The State of Maine Department of Environmental Protection found that all PBDEs should be banned.¹⁷ In August, 2003, the State of California outlawed the sale of penta- and octa- PBDE and products containing them, effective January 1, 2008.¹⁸ In May 2007, the legislature of the state of Maine passed a bill phasing out the use of DecaBDE.¹⁹

References

1. ^ Kellyn S. Betts (2001-12-07). "Rapidly rising PBDE levels in North America", Environmental Science & Technology. 
2. ^ Globe and Mail article "Common foods laced with chemical"
3. ^ [1] "Toxic Compounds in Toddlers & Preschoolers 3x Higher Than in Moms"
4. ^ "Developmental exposure to low-dose PBDE-99: effects on male fertility and neurobehavior in rat offspring" Environmental Health Perspectives 2005 volume 113, pp. 149–154. doi:10.1289/ehp.7421
5. ^ Lind Y, Darnerud PO, Atuma S, et al (October 2003). "Polybrominated diphenyl ethers in breast milk from Uppsala County, Sweden". Environ. Res. 93 (2): 186–94. doi:10.1016/S0013-9351(03)00049-5. PMID 12963403. 
6. ^ Lindberg P, Sellström U, Häggberg L, de Wit CA (January 2004). "Higher brominated diphenyl ethers and hexabromocyclododecane found in eggs of peregrine falcons (Falco peregrinus) breeding in Sweden". Environ. Sci. Technol. 38 (1): 93–6. PMID 14740722. 
7. ^ DIRECTIVE 2003/11/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL
8. ^ WebMD article "Fire Retardants Found in Children's Blood"
9. ^ Food Consumer article "Toxic Compounds in Toddlers & Preschoolers 3x Higher Than in Moms"
10. ^ Dye, J.A. (2007). "Elevated PBDE Levels in Pet Cats: Sentinels for Humans?". Environmental Science & Technology 41: 6350. doi:10.1021/es0708159. 
11. ^ A. Malmvärn, Y. Zebühr, L. Kautsky, Å. Bergman, L. Asplund (2008). "Hydroxylated and methoxylated polybrominated diphenyl ethers and Polybrominated dibenzo-p-dioxins in red alga and cyanobacteria living in the Baltic Sea". Chemosphere 72: 910–916. doi:10.1016/j.chemosphere.2008.03.036. 
12. ^ Emma L. Teuten, Li Xu, Christopher M. Reddy (2005). "Two Abundant Bioaccumulated Halogenated Compounds Are Natural Products". Science 307 (5711): 917–920. doi:10.1126/science.1106882. PMID 15705850. 
13. ^ [2] US Environmental Protection Agency. Toxicological Profile for Decabromodiphenyl ether (BDE-209) Integrated Risk Information System, June 2008.
14. ^ [3] US Environmental Protection Agency. Toxicological Profile for Pentabromodiphenyl ether (BDE-47) Integrated Risk Information System, June 2008.
15. ^ www.epa.gov/iris
16. ^ "Chemical ban puts industry on the defensive." State of Washington bans use of PBDEs.
17. ^ [4] "DEP urges legislative ban on fire retardant"
18. ^ "BILL NUMBER: AB 302, An act to add Chapter 10 (commencing with Section 108920) to Part 3 of Division 104 of the Health and Safety Code, relating to toxic substances."
19. ^ "Maine Legislature votes to ban toxic Deca flame retardant." State of Maine bans use of DecaBDE.

External links

• Sandy, Martha. Polybrominated Diphenyl Ethers: Recommendations to Reduce Exposure in California. Office of Environmental Health Hazard Assessment. 25 Apr. 2008
• Polybrominated diphenylethers (PBDEs) | Pollution Prevention and Toxics (OPPT) | Prevention, Pesticides and Toxics (OPPTS). U.S. Environmental Protection Agency. 25 Apr 2008
• [www.atsdr.cdc.gov/toxprofiles/tc6.. Chemical and Physical Information. Toxicology Profiles. 25 Apr. 2008 ]
• Environment and Science T pdf echnology article
• About.com article
• Environmental Working Groups 2003 report of record concentrations of PBDEs in American Mothers
• Northwest Environment Watch
• Survey of chemicals in the blood of European ministers, where PBDEs have been found in all blood samples
• PBDEs: They are everywhere, they accumulate and they spread
• Silicon Valley Toxics Coalition: BFRs in Electronics
• Study links cat disease to flame retardants in furniture and to pet food
• UCR: Chemicals Used as Fire Retardants Could Be Harmful, UCR Researchers Say

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• This page was last modified on 12 November 2008, at 21:23.

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