Polybrominated diphenyl ethers

Polybrominated diphenyl ethers (PBDEs) are a class of organohalogen compounds that are used as flame retardants. Found in a wide array of products including electronics, furnishings, motor vehicles, and building materials, PBDEs have been widely used to reduce the risk of fire. However, their environmental persistence, potential for bioaccumulation, and associated health risks have led to a reevaluation of their safety and the gradual phasing out of their use globally.

Chemical Structure and Properties

PBDEs consist of two benzene rings bonded together by an ether linkage, with varying numbers of bromine atoms attached to the rings, which can range from one to ten bromine atoms. This variability gives rise to several different congeners, grouped into commercial mixtures based on their degree of bromination, such as penta-, octa-, and deca-BDE. The physical and chemical properties of PBDEs, including their lipophilicity and persistence, vary with the degree of bromination.

Use and Applications

Historically, PBDEs have been used extensively as additive flame retardants. Unlike reactive flame retardants, which are chemically bound to materials, additive PBDEs are mixed into materials without forming a chemical bond. This has made them easier to use but also more likely to leach out into the environment. Major applications have included polyurethane foam in furniture, plastics in electronics, and textiles.

Environmental and Health Concerns

PBDEs are persistent in the environment and have been detected in air, water, soil, and wildlife, as well as in human tissues. They have the potential to bioaccumulate in the food chain, leading to higher concentrations in predators, including humans. Exposure to PBDEs has been associated with several adverse health effects, including thyroid hormone disruption, neurodevelopmental deficits in children, and potential links to cancer. These concerns have led to the phased-out production and use of certain PBDEs in many countries.

Regulation and Phasing Out

The recognition of the risks posed by PBDEs has led to international regulatory action. The Stockholm Convention on Persistent Organic Pollutants, which aims to eliminate or restrict the production and use of persistent organic pollutants (POPs), has listed certain PBDE congeners for elimination. Many countries have also implemented national bans or restrictions on the production, use, and import of various PBDE mixtures.

Alternatives

In response to the phasing out of PBDEs, the search for safer alternative flame retardants has intensified. Alternatives include chemicals with similar flame-retardant properties but lower toxicity and environmental persistence, as well as non-chemical approaches to fire safety, such as improved product design and the use of inherently flame-resistant materials.

See Also

• Flame retardant
• Persistent organic pollutant
• Bioaccumulation
• Endocrine disruptor