home


 * 1. Introduction to PBDEs**


 * 1.1 What are PBDEs?**

Polybrominated diphenyl ethers (PBDEs) are a commonly used flame-retardant. They are organobromine compounds and findings indicate that they are in fact toxic to the environment under the Canadian Environmental Protection Act (CEPA Environmental Registry Substances List, 2004). Families of PBDEs are called congeners and there are 209 potential substances that range from dibromodiphenyl ether up to decabromodiphenyl ether (Orazio et al, 2004). Exposure to PBDEs within a domestic environment occurs in numerous household items, mainly those containing plastics, electronic equipment and upholstery (Health Canada, 2009), as well as in salmon, ground beef, butter and cheese (Chao et al, 2010). PBDEs act as flame-retardants by breaking down at high temperatures releasing their bromine atoms, which then inhibit the chemical reactions that allow the fire to continue (Our Stolen Future, n.d.). Approximately 50,000 metric tonnes of PBDEs are produced globally each year, 40% of which are used in North America alone (Our Stolen Future, n.d.). PBDEs are considered to be persistent organic pollutants (POPs), highly toxic chemicals (ToxTown, 2010), and are easily stored in fat (Toxipedia, 2010). They are mixed into products in order to raise the temperature at which they burn (Toxipedia, 2010), however, PBDEs are easily released over time when products such as TVs and computers are heated or when they simply degrade (Toxipedia, 2010; Stiffler, 2007). A 25-year study conducted in Sweden has concluded that PBDE levels in people doubles about every 5 years, indicating that bioaccumulation of this product is a concern (Toxipedia, 2010).


 * 1.2 PBDE Structure**




 * Figure 1: PBDE structure** (International Programme on Chemical Safety, 1994)

Generally, there are classes of PBDEs. Lower brominated PBDEs contain 1-5 bromine atoms per molecule, and are more dangerous because they bioaccumulate faster. They are known to affect thyroid hormone levels and there seems to be a connection to reproductive and neurological risks (Orazio et al, 2004). Higher brominated PBDEs contain more than 5 bromine atoms per molecule and bioaccumulate less rapidly than lower brominated PBDEs (Orazio et al, 2004). Structurally, PBDEs are similar to polychlorinated biphenyls (PCBs) and both undergo significant bioaccumulation (Chao et al, 2010; Darnured et al, 2001).


 * Figure 2:** ** Comparison of PBDEs (top) and PCBs (bottom) **(Washington Policy Center, 2006).

As mentioned above, there are 209 different compounds, with the most common being decaBDE, octaBDE and pentaBDE, depending on the number of bromine atoms present. They break down more easily than other POPs because of the weak bond between carbon and bromine (Toxipedia, 2010; Schmidt 2003).

Due to the fact that PBDEs are added to products as opposed to chemically bound, they are continually released from the products both during their use and after their disposal (Health Canada, 2009).


 * 1.3 PBDE Uses**

PBDE use is extremely common. They are often found in electronic circuit boards and cases, cables, textiles, vehicles, synthetic building materials and carpet lines (Chao et al, 2010 reword). PBDEs are found in household dust ( Schecter et al, 2005; Wu et al, 2007), meat (Huwe and Larsen, 2005), fish (Zhu and Hites, 2004), as well as humans (Chao et al, 2010). They are added to materials to decrease the intensity of fires (Our Stolen Future, n.d.) .


 * 1.4 An Overview of the Types of PBDEs**


 * Deca & Octa** **BDE** are off-white solids and decaBDE constitutes 82% of PBDE products made each year (ToxTown, 2010). It is about 97% pure brominated diphenyl ether (Toxipedia, 2010) and can be found in textiles, electronics, and construction materials (ToxTown 2010; Birnbaum, 2004). Production of OctaBDE ceased in 2004 (Toxipedia 2010; Stiffler, 2007). DecaBDE is very controversial, and the United States produces nearly 50 million pounds of it each year. In addition, demand is anticipated to increase further because it is now approved for use to comply with safety standards at the federal level in residential furniture and mattresses (Toxipedia, 2010). Recently, many countries have banned octaBDE, one of the PBDEs considered to be the most harmful (Health Canada, 2009). The production, import, and sale of decaBDE is scheduled to end by December 31, 2012 and cannot be used beyond December 31, 2013 in the United States (ToxTown, 2010).


 * PentaBDE** is a thick liquid that is commonly found in foam cushions, rubber paints, adhesives, mattresses and car seats (ToxTown, 2010) and production ended in 2004 (Health Canada, 2009; Stiffler, 2007). PentaBDE is anywhere from 24-38% tetraBDE, 50-60% pentaBDE, and 4-6%HxBDE sources (Birnbaum, 2004) because commercial PBDE products are generally not a single compound, but rather a mixture of congeners.

Next page