Polybrominated biphenyls chemical structure

Fig. 7 Generic chemical structures of polyhalogenated compounds. X=C1, Br. (I) Polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs) (II) chlorophenols (CPs), bromophenols (BPs) (III) polychlorinated diphenyl ethers (PCDE), polybrominated diphenyl ethers (PBDE) (IV) polychlorinated dibenzo-p-dioxin (PCDD), polybrominated dibenzo-p-dioxin (PBDD) (V) polychlorinated dibenzofuran (PCDF), polybrominated dibenzofuran (PBDF) (VI) tetrabromobisphenol A (TBBPA)...

Polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) are each classes of structurally similar brominated hydrocarbons. PBBs are a class of chemical compounds in which 2 10 bromine atoms are attached to the biphenyl molecule. PBDEs are a class of chemical confounds in which 2 10 bromine atoms are attached to the diphenyl ether molecule. Monobrominated structures (i.e., one bromine atom attached to the molecule) are often included when describing PBBs and PBDEs. The general chemical structures of PBBs and PBDEs are similar when viewed in one dimension, differing only in an ether linkage, as shown below ... 

It is very likely that the polybrominated biphenyls are metabohzed in fish, sea mammals, and human to debrominated and hydroxylated polybrominated biphenyls. It is suggested by the authors that some of these polybrominated metabolites can bind to the estrogen receptor and act hke xenoestrogens, as was shown for hydroxy polychlorinated biphenyls (HO-PCBs) by Korach et al. [256], McKinney and Waller [257], and Waller et al. [258]. Especially the chemical structure of para-substituted hydroxylated metabohtes of polybrominated biphenyls would be similar to that of estradiol, preferably in the presence of... 

Table 15. Chemical name, trade name, CAS No., chemical structure, molecular formula, molecular weight, n-octanol/water partition coefficient (Kqw), bioconcentration factors on a lipid basis (BCFl) in fish, and residues found in environmental samples (sediments, mussels, fish) and human fat of Polybrominated Benzenes (PBBzs), Polybrominated Biphenyls (PBBs), and Polybrominated Diphenylethers (PBDEs)... 

Among the major ubiquitous SVOC pollutants in the urban air worldwide are polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Their chemical structures are presented in Figs. 1, 2. Theoretically, there are 57 individual PAHs which contain 2-6 fused six-member benzenoid rings only (Harvey 1997). There are 209 individual PCB congeners and 209 individual PBDE congeners, varying in the number and positions of the substitutions by chlorine and bromine, respectively. 

Brominated flame retardants are widely used as polymer additives in plastics, electric appliances, and textile and polyurethane foams. Some of the technical flame retardant products contain brominated organic compounds, including polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers. These compounds are structurally similar to PCBs and, therefore, their chemical properties, persistence, bioaccumulation, and distribution in the environment follow similar patterns. Moreover, they have potential endocrine disrupting properties and there are concerns over their exposure health effects. 

Neurotoxicity can also occur as a result of indirect effects. For example, damage to hepatic, renal, circulatory, or pancreatic structures may result in secondary effects on the function and structure of the nervous system, such as encephalopathy or polyneuropathy. Secondary effects would not cause a substance to be considered neurotoxic, though at high enough doses, neurotoxicity could be evident. Thus, for the purpose of this review, a substance is defined as neurotoxic when it or its metabolites produce adverse effects as a result of direct interactions with the nervous system. It should be noted, nevertheless, that some chemicals may have multiple modes of action and affect the nervous system directly and indirectly. For example, several halogenated compounds (e.g., polychlorinated biphenyls (PCB), polybrominated diphenyl ethers (PBDE)) may interact directly with brain cells, and also affect the development of the nervous system by altering thyroid hormone homeostasis.7 8... 

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