Hexabromocyclododecane
Encyclopedia
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 that is used as thermal insulation in the building industry. HBCD is highly efficient in this application so that very low levels are required to reach the desired flame retardancy. Typical HBCD levels in EPS are 0.7% and in XPS 2.5%. At present, according to BSEF, the brominated flame retardant industry panel, HBCD is the only suitable flame retardant for these applications. Any other flame retardant
would likely need higher load levels in the polystyrene foam. 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.
The industrial demand in Europe is estimated as 9500 tons per year.
HBCD's toxicity and its harm to the environment are currently discussed. HBCD can be found in environmental samples such as birds, mammals, fish and other aquatic organisms as well as soil and sediment.
On this basis, on 28 October 2008 the European Chemicals Agency
decided to include HBCD in the SVHC list, Substances of Very High Concern, within the Registration, Evaluation, Authorisation and Restriction of Chemicals framework.
HBCD has been found widely present in biological samples from remote areas and supporting evidences for its classification as Persistent, Bioaccumulative and Toxic (PBT
) and undergoes long-range environmental transportation.
Since August 2010 Hexabromocyclododecanes are included in the EPA's List of Chemicals of Concern.
Because HBCD has 16 possible stereo-isomers with different biological activities, the substance poses a difficult problem for manufacture and regulation. An article by Robin Law of the Centre for Environment, UK discusses this issue in depth.
The HBCD technical mixture is composed of three main diastereomers denoted as alpha (α), beta (β) and gamma (γ) with traces of others. A whole animal laboratory study in mice demonstrates that the predominant diastereomer
in the HBCD technical mixture, γ, undergoes rapid metabolism, elimination and biological conversion to other diastereomers. This is reported by David T Szabo of the University of North Carolina
in Chapel Hill, USA where after oral exposure to the γ diastereomer; β was detected in the liver and brain and α and β was detected in the fat and feces. The reported toxicokinetic behavior has important implications for the extrapolation of toxicological studies of the commercial HBCD mixture to the assessment of human risk
.
Due to its persistence
, toxicity, and ecotoxicity, a global ban on HBCD is currently being considered under the framework of the Stockholm Convention on Persistent Organic Pollutants
. HBCD is also included on the list of substances added to a proposal to revise the RoHS
(Restriction of Hazardous Substances) directive. There is a large and increasing stock of HBCD in the anthroposphere
, mainly in EPS and XPS insulation boards.
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
, eighteen hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, and six bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
atoms tied to the ring. Its primary application is in extruded (XPS) and expanded (EPS) polystyrene
Polystyrene
Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...
foam that is used as thermal insulation in the building industry. HBCD is highly efficient in this application so that very low levels are required to reach the desired flame retardancy. Typical HBCD levels in EPS are 0.7% and in XPS 2.5%. At present, according to BSEF, the brominated flame retardant industry panel, HBCD is the only suitable flame retardant for these applications. Any other flame retardant
Flame retardant
Flame retardants are chemicals used in thermoplastics, thermosets, textiles and coatings that inhibit or resist the spread of fire. These can be separated into several different classes of chemicals:...
would likely need higher load levels in the polystyrene foam. 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.
The industrial demand in Europe is estimated as 9500 tons per year.
HBCD's toxicity and its harm to the environment are currently discussed. HBCD can be found in environmental samples such as birds, mammals, fish and other aquatic organisms as well as soil and sediment.
On this basis, on 28 October 2008 the European Chemicals Agency
European Chemicals Agency
The European Chemicals Agency is an agency of the European Union which manages the technical, scientific and administrative aspects of the Registration, Evaluation, Authorisation and Restriction of Chemicals system...
decided to include HBCD in the SVHC list, Substances of Very High Concern, within the Registration, Evaluation, Authorisation and Restriction of Chemicals framework.
HBCD has been found widely present in biological samples from remote areas and supporting evidences for its classification as Persistent, Bioaccumulative and Toxic (PBT
Persistent organic pollutant
thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...
) and undergoes long-range environmental transportation.
Since August 2010 Hexabromocyclododecanes are included in the EPA's List of Chemicals of Concern.
Because HBCD has 16 possible stereo-isomers with different biological activities, the substance poses a difficult problem for manufacture and regulation. An article by Robin Law of the Centre for Environment, UK discusses this issue in depth.
The HBCD technical mixture is composed of three main diastereomers denoted as alpha (α), beta (β) and gamma (γ) with traces of others. A whole animal laboratory study in mice demonstrates that the predominant diastereomer
Diastereomer
Diastereomers are stereoisomers that are not enantiomers.Diastereomerism occurs when two or more stereoisomers of a compound have different configurations at one or more of the equivalent stereocenters and are not mirror images of each other.When two diastereoisomers differ from each other at...
in the HBCD technical mixture, γ, undergoes rapid metabolism, elimination and biological conversion to other diastereomers. This is reported by David T Szabo of the University of North Carolina
University of North Carolina
Chartered in 1789, the University of North Carolina was one of the first public universities in the United States and the only one to graduate students in the eighteenth century...
in Chapel Hill, USA where after oral exposure to the γ diastereomer; β was detected in the liver and brain and α and β was detected in the fat and feces. The reported toxicokinetic behavior has important implications for the extrapolation of toxicological studies of the commercial HBCD mixture to the assessment of human risk
Risk
Risk is the potential that a chosen action or activity will lead to a loss . The notion implies that a choice having an influence on the outcome exists . Potential losses themselves may also be called "risks"...
.
Due to its persistence
Persistent organic pollutant
thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...
, toxicity, and ecotoxicity, a global ban on HBCD is currently being considered under the framework of the Stockholm Convention on Persistent Organic Pollutants
Stockholm Convention on Persistent Organic Pollutants
Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants .- History :...
. HBCD is also included on the list of substances added to a proposal to revise the RoHS
Restriction of Hazardous Substances Directive
The Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment 2002/95/EC was adopted in February 2003 by the European Union. The RoHS directive took effect on 1 July 2006, and is required to be enforced and become law in each member state...
(Restriction of Hazardous Substances) directive. There is a large and increasing stock of HBCD in the anthroposphere
Anthroposphere
The anthroposphere is that part of the environment that is made or modified by humans for use in human activities and human habitats...
, mainly in EPS and XPS insulation boards.
External links
- An Overview of Alternatives to Tetrabromobisphenol A (TBBPA) and Hexabromocyclododecane (HBCD), University of Massachusetts Lowell, March 2006
- ECHA: MEMBER STATE COMMITTEE SUPPORT DOCUMENT FOR IDENTIFICATION OF HEXABROMOCYCLODODECANE AND ALL MAJOR DIASTEREOISOMERS IDENTIFIED AS A SUBSTANCE OF VERY HIGH CONCERN, 8 October 2008
- Factsheet BSEF - propaganda of producers of bromine chemicals
- Factsheet CEFIC-EFRA - propaganda of European chemical industry
- Greenwashing of bromine industry