Polybrominated diphenyl ethers or PBDEs, are a class of

organobromine compound Organobromine chemistry is the study of the synthesis and properties of organobromine compounds, also called organobromides, which are organic compounds that contain carbon bonded to bromine. The most pervasive is the naturally produced bromometh ...

s that are used as

flame retardant Flame retardants are a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an combustion, ignition source and pr ...

s. Like other

brominated flame retardant Brominated flame retardants (BFRs) are organobromine compounds that have an inhibitory effect on combustion chemistry and tend to reduce the flammability of products containing them. The brominated variety of commercialized chemical flame retarda ...

s, PBDEs have been used in a wide array of products, including building materials, electronics, furnishings, motor vehicles, airplanes, plastics,

polyurethane Polyurethane (; often abbreviated PUR and PU) is a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane term ...

foams, and textiles. They are structurally akin to polychlorinated diphenyl ethers (PCDEs),

polychlorinated biphenyl Polychlorinated biphenyls (PCBs) are organochlorine compounds with the formula Carbon, C12Hydrogen, H10−''x''Chloride, Cl''x''; they were once widely used in the manufacture of carbonless copy paper, as heat transfer fluids, and as dielectri ...

s (PCBs) and other polyhalogenated compounds, consisting of two

halogen The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...

ated aromatic rings. PBDEs are classified according to the average number of

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

atoms in the molecule. The life-saving benefits of fire retardants led to their popularization. Standards for mass transit vehicles continues to increase as of 2021. Because of their toxicity and persistence, all commercially relevant PBDEs have been marked for elimination under the Stockholm Convention, a treaty to control and phase out major

persistent organic pollutants Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic and adversely affect human health and the environment around the world. Becaus ...

(POPs).

Classes of PBDEs

The family of PBDEs consists of 209 possible substances, which are called congeners (PBDE = C₁₂H_(10−''x'')Br_''x''O (''x'' = 1, 2, ..., 10 = ''m'' + ''n'')). The number of

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the existence or possibili ...

for mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and

decabromodiphenyl ether Decabromodiphenyl ether (also referred to as decaBDE, DBDE, BDE-209) is a brominated flame retardant which belongs to the group of polybrominated diphenyl ethers (PBDEs). It was commercialised in the 1970s and was initially thought to be safe, but ...

s are 3, 12, 24, 42, 46, 42, 24, 12, 3 and 1, respectively. Lower-brominated PBDEs with 1–4

atoms per molecule are regarded as more dangerous because they more efficiently bioaccumulate. They have been known to affect

thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones triiodothyronine, T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus r ...

levels, and studies have linked them to reproductive and neurological risks at certain concentrations or higher. Higher-brominated PBDEs are less acutely dangerous but biotically and photochemically debrominate to lower-brominated congeners.

Production

PBDEs were produced commercially via the

bromination In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs ...

of diphenyl ether, with three technical-grade mixtures being sold, varying by degree of bromination. In the United States, PBDEs were marketed with the trade names DE-60F, DE-61, DE-62, and DE-71 applied to pentaBDE mixtures, DE-79 applied to octaBDE mixtures, and DE 83R and Saytex 102E applied to decaBDE mixtures. The available commercial PBDE products were not single compounds or even single congeners but rather mixtures of congeners. Technical pentaBDE predominantly contained pentabromo derivatives (50–62%); however, the mixture also contained tetrabromides (24–38%) and hexabromides (4–8%), as well as traces of the tribromides (0–1%). Technical octaBDE was a mixture of homologs: hexa-, hepta-, octa-, nona-, and decabromides. Technical decaBDE was 97% decabromide, with small amounts of octa- and nonabromides. Commercial production of PBDEs began in the 1970s, and continued until the early 2010s. Cumulative global production is estimated to have been 175kt for pentaBDE, 130kt for octaBDE, and 1600kt for decaBDE.

Health and environmental concerns

Exposure

Polybrominated diphenyl ethers (PBDEs) can be released into the environment where they are used or produced, possibly entering air, water, soil or the

human digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...

when consumed, inhaled or via the skin. Despite the banning and phase out of several forms of PBDEs, many consumer products still contain them in the 21st century, and represent potential exposure sources, including furniture and other consumer products containing

polyurethane foam Polyurethane foam is a solid polymeric foam based on polyurethane chemistry. As a specialist synthetic fibre, synthetic material with highly diverse applications, polyurethane foams are primarily used for thermal insulation and as a cushioning mat ...

, appliances, pipes, plastics, and old electronic equipment. Generally, governments have determined that PBDEs are not harmful to human health in the exposure amounts assessed. Ingestion of house

dust Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...

accounts for 80–90% of total PBDE exposure, while the remaining exposure occurs from food ingestion. PBDE-contaminated foods, particularly those high in fat content, such as fatty meats or fish, are possible sources of exposure. In

breastfeeding Breastfeeding, also known as nursing, is the process where breast milk is fed to a child. Infants may suck the milk directly from the breast, or milk may be extracted with a Breast pump, pump and then fed to the infant. The World Health Orga ...

infants, breast milk may be an exposure source because PBDEs can be present in the mother and her milk. Various other food items may contain PBDEs, including meat, meat products, dairy products, and seafood. PBDEs have not been detected beyond trace levels in water. In the environment, soils and sediments are the major deposits for PBDEs. PBDEs can enter soil from discarded products, such as in landfills. As

biosolids Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to us ...

(sewage) may contain PBDEs, exposure from soils or farmlands that have been fertilized with biosolids may occur.

Wildlife Wildlife refers to domestication, undomesticated animals and uncultivated plant species which can exist in their natural habitat, but has come to include all organisms that grow or live wilderness, wild in an area without being species, introdu ...

may have exposure by consuming foods containing PBDEs, whereas organisms that live in sediments may be contaminated by PBDEs.

Excretion

PBDEs and their

metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...

s are excreted mainly in the feces and some in the urine. Owing to their deposition in body fat stores, some PBDEs remain in the body for many years, and may enter the bodies of unborn babies via the

placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...

Research on health effects

Nothing certain has been established about the effects of PBDEs on human health. Most information regarding toxicity of PBDEs and their metabolites is from early-stage animal studies. Evidence for PBDE-mediated effects from human studies in systems other than the developing nervous system, such as in cancer development, is inconclusive or non-existent. Particularly for the potential effects of PBDEs on the developing fetus, research has focused on the health status of mothers and

gestational age In obstetrics, gestational age is a measure of the age of a pregnancy taken from the beginning of the woman's last menstrual period (LMP), or the corresponding age of the gestation as estimated by a more accurate method, if available. Such metho ...

of the infant.

Sediment contamination

Increasing environmental concentrations and changing distributions of PBDEs in sediments of the Clyde River Estuary in Scotland, UK have been assessed. Analysis of six sediment cores each of 1 m depth from

Glasgow Glasgow is the Cities of Scotland, most populous city in Scotland, located on the banks of the River Clyde in Strathclyde, west central Scotland. It is the List of cities in the United Kingdom, third-most-populous city in the United Kingdom ...

city to Greenock revealed that total concentrations increased toward the river bed surface (0–10 cm). Amounts of PBDE ranged from 1 to 2,645 µg/kg (dry wt. sediment) with a mean of 287 µg/kg (dry wt. sediment). Down-core PBDE congener profiles showed that higher concentrations were due to elevated levels of BDE-209. The majority of the sediment records clearly showed a change from mainly lower molecular weight BDEs 47,99, 183, 153 at lower depths to BDE-209 near the surface, a change in congener and homologue group patterns that corresponds to the restrictions of penta- and octaBDE commercial mixtures under EU law in 2004–2006. While biodegradation is not considered the main pathway for PBDEs,

photolysis Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons wi ...

and

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

can be of interest in studies of transformation of PBDEs.

Regulations of PBDEs

United States

In August 2003, the State of California outlawed the sale of penta- and octaBDE and products containing them, effective 1 January 2008. 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 indicates that PBDEs may possess liver toxicity, thyroid toxicity, and neurodevelopmental toxicity.US Environmental Protection Agency
Toxicological Profile for Decabromodiphenyl ether (BDE-209)
Integrated Risk Information System, June 2008.US Environmental Protection Agency
Toxicological Profile for 2,2',4,4',5-Pentabromodiphenyl ether (BDE-99)
Integrated Risk Information System, June 2008. In June 2008, the U.S. EPA set a safe daily exposure level ranging from 0.1 to 7 μg/kg body weight per day for the four most common PBDE congeners.US Environmental Protection Agency
Toxicological Profile for 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47)
Integrated Risk Information System, June 2008.US Environmental Protection Agency
Toxicological Profile for 2,2',4,4',5,5'-Hexabromodiphenyl ether (BDE-153)
Integrated Risk Information System, June 2008. In April 2007, the legislature of the state of Washington passed a bill banning the use of PBDEs."Chemical ban puts industry on the defensive."
State of Washington bans use of PBDEs. The State of

Maine Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...

Department of Environmental Protection has restrictions on PBDEs, and in 2008, the legislature passed a bill phasing out the use of decaBDE. The U.S. importers and manufacturers of PBDEs withdrew pentaBDE and octaBDE from sale in 2004, and decaBDE from sale by the end of 2013. In November 2024, the EPA added decaBDE to the Toxic Substances Control Act to prohibit release into water during manufacturing, processing or distribution in commerce of decaBDE and decaBDE-containing products, and a phase-out of processing and distribution of wire and cable insulation containing decaDBE for nuclear power facilities.

Canada

Since 2012, PBDEs are among chemicals prohibited from manufacture, use, sale, offer for sale or import, as regulated in the Prohibition of Certain Toxic Substances Regulations of the 1999 Canadian Environmental Protection Act. PBDEs are regarded in the regulation as "toxic to the environment and/or human health, are generally persistent, bioaccumulative, and/or inherently toxic."

European Union

The European Union decided to ban the use of two classes of flame retardants, in particular, PBDEs and

polybrominated biphenyl Polybrominated biphenyls (PBBs), also called brominated biphenyls or polybromobiphenyls, are a group of manufactured chemicals that consist of polyhalogenated compound, polyhalogenated derivatives of a biphenyl core. Their chlorine analogs are t ...

s (PBBs) in electric and electronic devices. This ban was formalised in the

RoHS The Restriction of Hazardous Substances Directive 2002/95/EC (RoHS 1), short for Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment, was adopted in February 2003 by the European Uni ...

Directive, and an upper limit of 1 g/kg for the sum of PBBs and PBDEs was set. In February 2009, the

Institute for Reference Materials and Measurements The Institute for Reference Materials and Measurements (IRMM), located in Geel, Belgium, is one of the seven institutes of the Joint Research Centre (JRC), a Directorate-General of the European Commission (EC). The IRMM promotes a common and relia ...

released two certified reference materials to help analytical laboratories better detect these two classes of flame retardants. The reference materials were custom-made to contain all relevant PBDEs and PBBs at levels close to the legal limit.

International

At an international level, in May 2009 the Parties of the

Stockholm Convention on Persistent Organic Pollutants Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed on 22 May 2001 in Stockholm and effective from 17 May 2004, that aims to eliminate or restrict the production and use of persistent organi ...

(POPs) decided to list commercial pentaBDE and commercial octaBDE as POP substances. This listing is due to the properties of hexaBDE and heptaBDE, which are components of commercial octaBDE, and to the properties of tetraBDE and pentaBDE, which are the main components of commercial pentaBDE. In 2017, it was decided to also list decaBDE.

Alternatives

Major decaBDE producers have switched to manufacturing decabromodiphenyl ethane, a structurally related compound that has also come under suspicion as an environmental pollutant. Non-halogenated alternatives also exist.

References

External links

U.S. EPA. An Exposure Assessment of Polybrominated Diphenyl Ethers. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/086F, 2010

Sandy, Martha. Polybrominated Diphenyl Ethers: Recommendations to Reduce Exposure in California. Office of Environmental Health Hazard Assessment. 25 Apr. 2008

Polybrominated diphenylethers (PBDEs) , U.S. Environmental Protection Agency
{{DEFAULTSORT:Polybrominated Diphenyl Ethers Flame retardants Endocrine disruptors Persistent organic pollutants under the Stockholm Convention Bromoarenes Diphenyl ethers