Polybrominated diphenyl ethers (PBDE) are increasingly used as flame retardants (presently 180,000 tons/year).
They are currently used in plastic components of computers and televisions, circuit boards, seats of cars and buses, and textiles. It is important to distinguish between additive and reactive uses. Reactive fire retardants such as TBBPA, are covalently bonded to the plastic itself, while additives, such as PBDEs, are only dissolved in the material. This means that reactive flame retardants are less likely to leach out or volatilize, whereas additives are more easily released.
Additive flame retardants are incorporated as components of plastic mixtures either before, during, or, more frequently, following polymerization. They are sometimes volatile and can tend to bleed, so flame retardancy may be gradually lost. High molecular-weight, plastic products, developed to enable plastics to be made more permanently fire retardant, use the additive method for fire-retardant protection. PBDEs. are the most widely used brominated flame retardant additives.
They bioaccumulate in marine mammals, birds and humans. Levels in human milk recently started to rise sharply, up to 4 ng/g lipid. The presence of lipophilic compounds in maternal milk reflects the body burden of the maternal organism and indicates the possibility of prenatal transplacental exposure as well as postnatal exposure through milk.
In contrast to polychlorinated biphenyls (PCB), very little information is available on the toxicity of PBDE. This is particularly true for developmental neurotoxicity, but recent experimental evidence indicates a potential of adverse effects on the developing nervous system. They affact behavioral development, neurotransmitter systems and receptors, intracellular signal transduction pathways, neuroendocrine mechanisms and have possible effects on glial function.
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