Hexabromocyclododecane: Difference between revisions

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| PIN = 1,2,5,6,9,10-Hexabromocyclododecane

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| Abbreviations = HBCDD<br />HBCD

| CASNo_Ref = {{cascite|correct|PubChem}}<ref>https://treaties.un.org/doc/Publication/CN/2013/CN.934.2013-Eng.pdf {{Bare URL PDF|date=March 2022}}</ref>

| CASNo = 3194-55-6

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| ChEBI = 134063

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| UNII = 66OON1WWOS

| EINECS = 221-695-9

| PubChem = 18529

| ChemSpiderID = 17499

| ChEMBL = 375298

| StdInChI=1S/C12H18Br6/c13-7-1-2-8(14)10(16)5-6-12(18)11(17)4-3-9(7)15/h7-12H,1-6H2

| StdInChIKey = DEIGXXQKDWULML-UHFFFAOYSA-N

| SMILES = C1(Br)C(Br)CCC(Br)C(Br)CCC(Br)C(Br)CC1}}

|Section2={{Chembox Properties

| MolarMass = 641.7 g/mol

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| MeltingPtC = 186

| MeltingPt_notes = (175–195 °C, depending upon isomer)

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|Section7={{Chembox Hazards

| GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}}

| GHSSignalWord = Warning

| HPhrases = {{H-phrases|315|319|335|361|362|410}}

| PPhrases = {{P-phrases|201|202|260|261|263|264|270|271|273|280|281|302+352|304+340|305+351+338|308+313|312|321|332+313|337+313|362|391|403+233|405|501}}

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'''Hexabromocyclododecane''' ('''HBCD''' or '''HBCDD''') is a [[brominated flame retardant]]. It consists of twelve [[carbon]], eighteen [[hydrogen]], and six [[bromine]] atoms tied to the ring. Its primary application is in extruded (XPS) and expanded (EPS) [[polystyrene]] foam used as thermal insulation in construction. Other uses are upholstered furniture, automobile interior textiles, car cushions and insulation blocks in trucks, packaging material, video cassette recorder housing, and electric and electronic equipment. According to UNEP, "HBCD is produced in China, Europe, Japan, and the USA. The known current annual production is approximately 28,000 tonnes per year. The main share of the market volume is used in Europe and China" (figures from 2009 to 2010).<ref>^ UNEP Stockholm Convention HBCD Risk management evaluation http://chm.pops.int/Convention/POPsReviewCommittee/Chemicals/tabid/243/Default.aspx</ref> Due to its [[persistent organic pollutant|persistence]], toxicity, and [[ecotoxicity]], the Stockholm Convention on Persistent Organic Pollutants decided in May 2013 to list hexabromocyclododecane in Annex A to the convention with specific exemptions for production and use in expanded polystyrene and extruded polystyrene in buildings. Because HBCD has 16 possible [[Stereoisomerism|stereo-isomers]] with different biological activities, the substance poses a difficult problem for manufacture and regulation.

==Toxicity==

HBCD's toxicity and its harm to the environment are current sources of concern. HBCD can be found in environmental samples such as birds, mammals, fish, and other aquatic organisms as well as soil and sediment.<ref>{{cite journal|pmid=16830527|year=2006|last1=Covaci|first1=A|last2=Gerecke|first2=AC|last3=Law|first3=RJ|last4=Voorspoels|first4=S|last5=Kohler|first5=M|last6=Heeb|first6=NV|last7=Leslie|first7=H|last8=Allchin|first8=CR|last9=De Boer|first9=J|title=Hexabromocyclododecanes (HBCDs) in the environment and humans: A review|volume=40|issue=12|pages=3679–88|journal=Environmental Science & Technology|doi=10.1021/es0602492|bibcode=2006EnST...40.3679C|url=https://research.vu.nl/ws/files/2182133/192859.pdf}}</ref>

On this basis, on 28 October 2008, the [[European Chemicals Agency]] decided to include HBCD in the [[SVHC]] list,<ref>{{cite web|url=http://echa.europa.eu/chem_data/candidate_list_table_en.asp |title=ECHA SVHC Official List |publisher=Echa.europa.eu |date=2011-12-19 |accessdate=2012-06-20 |url-status=dead |archiveurl=https://web.archive.org/web/20090318120401/http://echa.europa.eu/chem_data/candidate_list_table_en.asp |archivedate=2009-03-18 }}</ref> Substances of Very High Concern, within the [[Registration, Evaluation, Authorisation and Restriction of Chemicals]] framework. On 18 February 2011, HBCD was listed in the Annex XIV of REACH and hence is subject to Authorisation. HBCD can be used until the so-called “sunset date” (21 August 2015). After that date, only authorised applications will be allowed in the EU.

HBCD has been found widely present in biological samples from remote areas and supporting evidences for its classification as [[Persistent, bioaccumulative and toxic substances|Persistent, Bioaccumulative, and Toxic]] (PBT) and undergoes long-range environmental transportation.<ref>{{cite web|url=http://echa.europa.eu/doc/candidate_list/svhc_supdoc_hbccd_publication.pdf |title=ECHA HBCD SVHC Supporting Documentation |publisher=Echa.europa.eu |accessdate=2012-06-20 |url-status=dead |archiveurl=https://web.archive.org/web/20111026141835/http://echa.europa.eu/doc/candidate_list/svhc_supdoc_hbccd_publication.pdf |archivedate=2011-10-26 }}</ref>

In July 2012, an EU-harmonized classification and labeling for HBCD entered into force. HBCD has been classified as a category 2 for reproductive toxicity.<ref>Commission Regulation (EU) No 618/2012 of 10 July 2012 amending, for its adaptation to technical and scientific progress, Regulation (EC) No 1272/2008 of the European Parliament and of the Council on classification, labeling and packaging of substances and mixtures.http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2012:179:0003:0010:EN:PDF</ref> Since August 2010 hexabromocyclododecanes are included in the [[United States Environmental Protection Agency|EPA]]'s List of Chemicals of Concern.<ref>{{cite web|url=http://www.epa.gov/oppt/existingchemicals/pubs/actionplans/hbcd.html |title=EPA action details on HBCD |publisher=Epa.gov |accessdate=2012-06-20 |url-status=dead |archiveurl=https://web.archive.org/web/20120511162836/http://www.epa.gov/oppt/existingchemicals/pubs/actionplans/hbcd.html |archivedate=2012-05-11 }}</ref>

In May 2013 the Stockholm Convention on Persistent Organic Pollutants (POPs) decided to include HBCD in the convention's Annex A for elimination, with specific exemptions for expanded and extruded polystyrene in buildings needed to give countries time to phase in safer substitutes. HBCD is listed for elimination, but with a specific exemption for expanded polystyrene (EPS) and extruded polystyrene (XPS) in buildings. Countries may choose to use this exemption for up to five years after the request for exemption is submitted.<ref>https://treaties.un.org/doc/Publication/CN/2013/CN.934.2013-Eng.pdf {{Bare URL PDF|date=March 2022}}</ref> Japan was the first country to implement a ban on the import and production of HBCD effective in May 2014.

Because HBCD has 16 possible [[Stereoisomerism|stereo-isomers]] with different biological activities, the substance poses a difficult problem for manufacture and regulation.<ref>{{cite web|url=http://www.empa.ch/plugin/template/empa/*/54785/---/l=2|title=Hexabromocyclododecane Challenges Scientists and Regulators|date=|accessdate=2012-06-20}}</ref>

The HBCD commercial mixture is composed of three main diastereomers denoted as alpha (α-HBCD), beta (β-HBCD), and gamma (γ-HBCD) with traces of others. A series of four published in vivo mice studies were conducted between several federal and academic institutions to characterize the toxicokinetic profiles of individual HBCD stereoisomers. The predominant [[diastereomer]] in the HBCD mixture, γ-HBCD, undergoes rapid hepatic metabolism, fecal and urinary elimination, and biological conversion to other diastereomers with a short biological [[half-life]] of 1–4 days. After oral exposure to the γ-HBCD diastereomer, β-HBCD was detected in the liver and brain, and α-HBCD and β-HBCD was detected in the fat and feces <ref>{{cite journal |vauthors=Szabo DT, Diliberto JJ, Hakk H, Huwe JK, Birnbaum LS|title=Toxicokinetics of the flame retardant hexabromocyclododecane gamma: effect of dose, timing, route, repeated exposure, and metabolism |journal=Toxicological Sciences |volume=117 |issue=2 |pages=282–93 |year=2010 |doi=10.1093/toxsci/kfq183|pmid=20562218 |doi-access=free }}</ref> with multiple novel metabolites identified - monohydroxy-pentabromocyclododecane, monohydroxy-pentabromocyclododecene, dihydroxy-pentabromocyclododecene, and dihydroxy-pentabromocyclododecadiene.<ref>{{cite journal |vauthors=Hakk H, Szabo DT, Huwe J, Diliberto J, Birnbaum LS|title= Novel and distinct metabolites identified following a single oral dose of α- or γ-hexabromocyclododecane in mice |journal=Environmental Science and Technology |volume=46 |issue=24 |pages=13494–503 |year=2012 |doi=10.1021/es303209g |pmid= 23171393 |pmc= 3608416 |bibcode= 2012EnST...4613494H }}</ref> In contrast, α-HBCD is more biologically persistent, resistant to metabolism, bioaccumulates in lipid-rich tissues after a 10-day repeated exposure study, and has a longer biological half-life of up to 21 days; only α-HBCD was detected in the liver, brain, fat and feces with no stereoisomerization to γ-HBCD or β-HBCD and low trace levels of four different [[hydroxylated]] metabolites were identified.<ref>{{cite journal |vauthors=Szabo DT, Diliberto JJ, Hakk H, Huwe JK, Birnbaum LS|title=Toxicokinetics of the flame retardant hexabromocyclododecane alpha: effect of dose, timing, route, repeated exposure, and metabolism |journal=Toxicological Sciences |volume=121 |issue=2 |pages=234–44 |year=2011 |doi=10.1093/toxsci/kfr059 |pmid=21441408 |doi-access=free }}</ref> Developing mice had higher HBCD tissue levels than adult mice after exposure to either α-HBCD or γ-HBCD indicating the potential for increased susceptibility of the developing young to HBCD effects.<ref>{{cite journal |vauthors=Szabo DT, Diliberto JJ, Huwe JK, Birnbaum LS|title=Differences in tissue distribution of HBCD alpha and gamma between adult and developing mice |journal=Toxicological Sciences |volume=123 |issue=1 |pages=256–63 |year=2011 |doi=10.1093/toxsci/kfr161|pmid=21705717 |doi-access=free }}</ref> The reported [[toxicokinetic]] differences of individual HBCD diastereoisomers have important implications for the extrapolation of toxicological studies of the commercial HBCD mixture to the assessment of human [[risk]].

==Environmental Concerns==

{{Update-section|date=January 2020}}

Due to its [[persistent organic pollutant|persistence]], toxicity, and [[ecotoxicity]], the Stockholm Convention on Persistent Organic Pollutants decided in May 2013 to list hexabromocyclododecane in Annex A to the convention with specific exemptions for production and use in expanded polystyrene and extruded polystyrene in buildings. Countries may choose to use this exemption for up to five years after the request for exemption is submitted.<ref>https://treaties.un.org/doc/Publication/CN/2013/CN.934.2013-Eng.pdf {{Bare URL PDF|date=March 2022}}</ref>

There is a large and still increasing stock of HBCD in the [[anthroposphere]], mainly in EPS and XPS insulation boards.<ref>[https://web.archive.org/web/20150626110220/http://www.geopartner.ch/upload/FABRO_2007.pdf Dynamic Substance Flow Analysis Model for Selected Brominated Flame Retardants as a Base for Decision Making on Risk Reduction Measures], study for the Swiss National Science Foundation, 2007</ref>

A long-term environmental monitoring program run by the Fraunhofer Institute for Molecular Biology and Applied Ecology demonstrates a general trend that HBCD concentrations are decreasing over time.<ref>Fraunhofer: H. Rüdel, J. Müller, M. Quack, R. Klein, 2012: Monitoring of hexabromo¬cyclodo¬decane diastereomers in fish from European freshwaters and estuaries. Environ. Sci. Pollut. Res. 19, 772-783 “Environmental Monitoring of HBCD in Europe” [[Society for Environmental Toxicology and Chemistry]] Europe – SETAC: Ecosystem Protection in a Sustainable World: a challenge for science and regulation. 2011. http://publica.fraunhofer.de/documents/N-217320.html</ref> HBCD emissions into the environment are controlled under the voluntary industry emission management program: the Voluntary Emissions Control Action Programme (VECAP).<ref>VECAP website: www.vecap.info</ref> The VECAP annual report demonstrates a continuous decrease of potential emissions of HBCD to the environment.<ref>{{Cite web|url=http://www.vecap.info/flipbook/annual2012/index.html|title = Maintaining Momentum European Annual Progress Report 2012}}</ref>

==References==

{{Reflist}}

==External links==

{{Commons category|Hexabromocyclododecanes}}

* [http://www.mpi-chemie.com/product/milebrome-fr-50.html MPI Milebrome B-972, FR 50 & GC SAM: The low-cost alternatives to Hexabromocyclododecane (HBCD) in EPS and XPS applications] {{Webarchive|url=https://web.archive.org/web/20131112145949/http://www.mpi-chemie.com/product/milebrome-fr-50.html |date=2013-11-12 }}, Stockholm Convention on Persistent Organic Pollutants 2012

* [http://sustainableproduction.org/downloads/AternativestoTBBPAandHBCD.pdf An Overview of Alternatives to Tetrabromobisphenol A (TBBPA) and Hexabromocyclododecane (HBCD)], [[University of Massachusetts]] Lowell, March 2006

* [[ECHA]]: [https://web.archive.org/web/20111026141835/http://echa.europa.eu/doc/candidate_list/svhc_supdoc_hbccd_publication.pdf MEMBER STATE COMMITTEE SUPPORT DOCUMENT FOR IDENTIFICATION OF HEXABROMOCYCLODODECANE AND ALL MAJOR DIASTEREOISOMERS IDENTIFIED AS A SUBSTANCE OF VERY HIGH CONCERN], 8 October 2008

* [https://web.archive.org/web/20130807005643/http://www.bsef.com/uploads/Documents/documents/Factsheet_HBCD_25-10-2012.pdf Factsheet BSEF]

* [http://www.bsef.com/env_health/hbcd BSEF – the bromine industry website’s page on HBCD] {{Webarchive|url=https://web.archive.org/web/20060829031425/http://www.bsef.com/env_health/hbcd/ |date=2006-08-29 }}

[[Category:PBT substances]]

[[Category:Persistent organic pollutants under the Stockholm Convention]]