Tetrabromodiphenyl ether,
Pentabromodiphenyl ether

Brominated diphenylethers PBDEs are flame-retardant chemicals that are added to a variety of consumer products to make them difficult to burn. Because PBDEs are added rather than reacted to the product, they could leave the product under ideal conditions and enter the environment, but this rarely happens. The first commercial productions of PBDEs began in the 1970s in Germany. Production of PBDEs has continued until the present. There are three commercial PBDE products (i.e., penta-, octa-, and decabromodiphenyl ethers). Deca- and octa-brominated types of PBDEs are also produced outside of the United States (in China and Israel). Decabromodiphenyl ether (decaBDE) makes up 82% of these products manufactured globally. PBDEs have not been associated with actual health-related effects. Concerns have increased, however, because some of these chemicals (particularly the pentaBDEs) have been found in the environment at varying concentrations. Environmental concentrations of lower brominated PBDEs, which may be leveling off in Europe, appear to be increasing in certain areas of Canada and the United States. PBDEs are a group of synthetic organic chemicals with no known natural sources in the environment, except for a few marine organisms that produce forms of PBDEs that contain higher levels of oxygen. Commercial decaBDE and octaBDE products are colorless to off-white solids, whereas commercial pentaBDE product is a thick liquid. PBDEs are not expected to evaporate into the air. PBDEs in the air are mostly found with dust rather than as a vapor. PBDEs enter the environment as mixtures containing a variety of individual brominated diphenyl ether (for PBDEs) components, known as congeners. Congeners are distinct members of a class of chemical substances. Some commercial mixtures of PBDEs may be known by their industrial trade names, (i.e., DE-60F Special, DE-61, DE-62, DE-71, DE-79, DE 83R, Saytex® 102E).

Polybrominated diphenyl ethers (PBDEs) are man-made chemicals found in plastics used in a variety of consumer products to make them difficult to burn. Very little is known about the health effects of PBDEs in people, but effects have been reported in animals. PBDEs have not been found in any of the 1,647 current or former National Priority List (NPL) sites identified by the Environmental Protection Agency (EPA).

Its main use is for electronic enclosures, such as television cabinets. Octabromodiphenyl ether (octaBDE) product is used in plastics for business equipment. Pentabromodiphenyl ether (pentaBDE) product is used in foam for cushioning in upholstery.

PBDEs enter air, water, and soil during their manufacture and use in consumer products. When PBDEs are suspended in air, they can be present as particles. They eventually return to land or water as the dust settles and are washed out by snow and rainwater. It is not yet possible to say how long PBDEs remain in the air. PBDEs do not dissolve easily in water, and therefore, high levels of PBDEs are not found in water. The very small amounts of PBDEs that do occur in water stick to particles and eventually settle to the bottom. Sediments at the bottom of bodies of water, such as lakes and rivers, generally act as reservoirs for decaBDEs, which can remain there for years. Some lower brominated PBDEs (e.g., tetra- and penta-congeners of PBDE) in water may build up in fish to low concentrations (about 10 billionths of a gram to 1 millionth of a gram of PDBE per gram of fresh fish [or 10x10^-9-1x10^-6 grams of PBDE per gram of fresh fish]). However, higher brominated PBDEs, such as decaBDE, are not found in fish at measurable concentrations. In general, the breakdown of PBDEs in soil is very slow, so they may remain in soil for several years. PBDEs bind strongly to soil particles. Rainwater is not expected to spread them much below the soil surface; thus, it is unlikely that PBDEs will enter groundwater.

Polybrominated diphenyl ethers have not been reported to occur naturally in the environment, but other types of brominated diphenyl ethers have been found in marine organisms. The presence in the environment of some of the brominated diphenyl ethers has been documented, the highest concentration being 1 g/kg sediment in streams or ponds in the vicinity of a manufacturing facility. Data on environmental fate, although limited to MBDE, DiBDE, and DeBDE, suggest that biodegradation is not an important degradation pathway for the PBDE, but that photodegradation may play a significant role.

Nothing definite is known about the health effects of PBDEs in people. Practically all of the available information is from studies of laboratory animals. Animal studies indicate that commercial decaBDE mixtures are generally much less toxic than the products containing lower brominated PBDEs. Because of its very different toxicity, decaBDE is expected to have relatively little effect on the health of humans. Rats and mice that ate food containing moderate amounts of lower brominated PBDEs for short periods of time had mainly thyroid effects. Rats and mice that ate smaller amounts over several weeks or months developed effects in the liver and in the thyroid. It is speculated that many of the thyroid effects of PBDEs are specific to the species of test animals, suggesting that they are less likely to occur in humans. Subtle behavioral changes have been observed in animals exposed to PBDEs as infants. One possible explanation for the behavioral effects might be related to changes in the thyroid, because development of the nervous system is dependent on thyroid hormones. PBDEs have not caused other kinds of birth defects in animals, but more studies are needed to determine if PBDEs can impair reproduction. Preliminary findings from short-term animal studies suggest that some PBDEs might impair the immune system. Animals exposed to PBDEs by skin contact showed signs of skin irritation only if they had been scratched. We don't know if PBDEs can cause cancer in people, although liver tumors developed in rats and mice that ate extremely large amounts of decaBDE throughout their lifetime. On the basis of evidence for cancer in animals, decaBDE is classified as a possible human carcinogen by EPA. Lower brominated PBDEs have not yet been tested for cancer. Neither the U.S. Department of Health and Human Services (DHHS) nor the International Agency for Research on Cancer (IARC) have classified the carcinogenicity of any PBDEs. We don't know whether the effects found in animals exposed to PBDEs would also occur in people exposed in the same way. The amounts of PBDEs that caused health effects in animals are much greater than levels of PBDEs normally found in the environment. Long-term exposure to PBDEs has a greater potential to cause health effects than does short-term exposure to low levels because of their tendency to build up in your body over many years. Additionally, the lower brominated commercial pentaBDE and octaBDE products are much more likely to cause health effects than is decaBDE.

Several methods to determine residues of PBDE in various media (air, sewage sludge, sediment, human adipose tissue, marine organisms, fish, and feed) as well as in commercial products have been reported. In general, sample extraction and clean-up techniques for the analysis of PBDE residues in biological samples are similar to those developed for PBB (see EHC 152: Polybrominated biphenyls), though the chromatographic conditions have to be modified in view of the long retention times of the highly brominated PBDE. Temperature programming and the use of capillary columns have been found to be very useful for the separation of the different congeners of PBDE. Recovery for the different PBDE is generally higher than 80%. Most methods are based on extraction with organic solvents, such as hexane/acetone, hexane/diphenyl ether, acetone, etc, purification of the extracts by gel permeation or adsorption chromatography, and determination mainly by gas chromatography, either with electron capture detection (ECD), or, coupled with mass spectrometry (MS). A multi-residue method has also been developed that includes a multi-step separation enabling the determination of several polychlorinated and polybrominated pollutants in biological samples.

[1] Wania, F., Dugani, C.B. (2003) Assessing the long-range transport potential of polybrominated diphenyl ethers: A comparison of four multimedia models. Environ. Toxicol. Chem. 22, 1252–1261.

[2] US EPA. [2009]. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.00]. United States Environmental Protection Agency, Washington, DC, USA

[3] Tittlemier, S.A., Tomy, G.T. (2001) Vapor pressures of six brominated diphenyl ether congeners. Environ. Toxicol. Chem. 20, 146–148.

[4] IPCS: Intox Databank, http://www.intox.org/databank/index.htm

[5] ATSDR: Agency for toxic substances and disease registery, http://www.atsdr.cdc.gov/

[6] TOXNET: TOXikology Data NETwork TOXNET - http://toxnet.nlm.nih.gov/

[7] IRZ: Integrovaný registr znečišťování životního prostředí (IRZ) : http://www.irz.cz/