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Brominated Flame Retardants
KODAVANTI, PRASADA RAO S., D. Szabo, T. E. STOKER, AND S. E. FENTON. Brominated Flame Retardants. Chapter 40, Dr. Ramesh Gupta (ed.), Reproductive and Developmental Toxicology. ELSEVIER, AMSTERDAM, Holland, 1:523-541, (2011).
This book chapter covers both developmental and reproductive effects of brominated flame retardants (BFRs) with emphasis on polybrominated diphenyl ethers (PBDEs). BFRs belong to a large group of organohalogen chemicals. They are highly persistent, bioaccumulative and cause adverse effects in humans and wildlife. Although some BFRs are banned or voluntarily withdrawn from usage by the manufacturer, emerging and existing BFRs continue to be used in industrialized countries. Because of the widespread use and large quantities of these chemicals in consumer products and household items, indoor contamination is proposed to be a significant source of human exposure. Other exposure routes are oral -both via breast milk, fat-containing foods, hand to mouth activity, etc. Recent epidemiological studies clearly indicated that BFRs affect human health. The human health effects include cryptorchidism, alterations in thyroid hormone homeostasis, reproductive effects, and reduced development of children at school age that include psychomotor development index and IQ performance. Studies have also indicated that the infant daily exposure dose of PBDEs due to inhalation, accidental oral ingestion and dermal absorption of house dust was significantly higher than that of the adults. Many rodent studies have confirmed that developmental exposure to these compounds should be limited. Studies in rodents indicated that several BFRs are developmental neurotoxicants affecting the nervous system growth and function. Several studies have also confirmed that the brominated flame retardants are indeed endocrine disruptors, with the potential to disrupt male and female reproductive development and adult reproductive function by having anti-androgenic actions (males) and by altering steroidogenic activities. This has been demonstrated in several in vivo studies using rodent models and by in vitro systems to determine effects on receptor binding (AR and PXR) and on steroidogenesis. These potential modes of action may be relevant to humans. This is incredibly important to consider as there have been several reports of adverse health consequences associated with increased PBDE exposure in humans in the last few years. Further research is needed to determine the long-term adverse consequences of exposures to the BFR described herein as well as a number of emerging replacement chemicals coming onto the market, as these compounds are known to bioaccumulate and can be transplacentally and lactationally transferred.
Brominated flame retardants (BFRs) belong to a large class of compounds known as organohalogens. BFRs are currently the largest marketed flame retardant group due to their high performance efficiency and low cost. In the commercial market, more than 75 different BFRs are recognized. Some BFRs, such as the polybrominated biphenyls (PBB), were removed from the market in the early 1970s after an incidental poisoning resulted in the loss of livestock due to the ingestion of PBB contaminated animal feed, which demonstrated the toxicity of this BFR class (Mercer et al., 1976; Fries, 1985). "Tris-BP" is another BFR that was removed from children's clothing due to its mutagenic and nephrotoxic effects, but have been used in children's pajamas (Soderlund et al., 1980). Of the BFRs still on the market, brominated bisphenols, diphenyl ethers and cyclododecanes are three major classes which represent the highest production volumes. These BFRs are used as additive or reactive components in a variety of polymers such as foam, high-impact polystyrene, and epoxy resins, which are then used in commercial products such as computers, electronics and electrical equipment, textiles, and furniture foam.