Biphenyl polyhalogenated

In 1979, it was stated that poiybrominated aromatic ethers have received little attention (ref. 1). That statement is still applicable. Analyses to characterize this class of commercial flame retardants have been performed using UV (refs. 1-2), GC (refs. 1-6), and GC-MS (refs. 1-4). The bromine content of observed peaks was measured by GC-MS, but no identification could be made. The composition of poiybrominated (PB) diphenyl ether (DPE) was predicted from the expected relationship with polyhalogenated biphenyl, a class which has received extensive attention. NMR (refs. 3-6) was successfully used to identify relatively pure material which had six, or fewer, bromine atoms per molecule. A high performance liquid chromatography (HPLC) method described (ref. 1) was not as successful as GC. A reversed phase (RP) HPLC method was mentioned, but no further work was published. 

Anaerobic dehalogenation has also been observed in aromatic ethers including polychlorinated dibenzo[l,4]dioxins (Fennell et al. 2004 Yoshida et al. 2005). The anaerobic debromination of decabromodiphenyl ether is considered here since it is analogous to the dehalogenation of polyhalogenated biphenyls. 

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)...

Hepatic Effects. Hepatic changes were observed in one chronic human exposure to mirex, as well as in a number of workers exposed to chlordecone for intermediate or chronic durations. In the mirex study, human subjects (sex and number not specified) from a chronically exposed cohort from southeast Ohio (route of exposure not specified, assumed to be oral) were assessed for cytochrome P- 4501A2 induction using a breath test that measures caffeine metabolism. The subjects exposed to mirex had elevated caffeine metabolism as compared to negative control individuals (subjects with no known exposure to polyhalogenated biphenyls or other related chemicals) in which the metabolism did not increase (Lambert et al. 1992). In the chlordecone study, liver function and structure in 32 men exposed to high levels of chlordecone while employed for 1-22 months (5.6... 

Lainbert GH, Hsu CC, Humphrey H, et al. 1992. Cytochrome P4SOIA2 in vivo induction a potential biomarker of polyhalogenated biphenyls and their related chemical s effects on the human. Chemosphere 25(1 -2) 197-200. 

Ethylmorphine and benzphetamine are N-demethylated specifically by rodent cytochrome(s) P-450 (as opposed to cytochrome(s) P] -450) in the rat phenobarbital and the polyhalogenated biphenyls induce these demethylation reactions. However, it is clear that no such stimulation occurred in the rainbow trout (Table II). 

On the other hand, the metabolism of benzo[a]pyrene, ethoxy-coumarin and ethoxyresorufin, which are preferentially oxidized by rodent cytochrome P -450, was greatly induced by the polyhalogenated biphenyls and 3-naphthoflavone. Despite large changes in... 

The data so far presented indicates that monooxygenation may be induced in the rainbow trout by polyhalogenated biphenyls and polycyclic aromatic hydrocarbons, but not by phendbarbital-type inducing agents. 

Specific considerations of metabolism and accumulation are not necessary in the application of a TTC provided that the substances are not likely to show very large species differences in accumulations such as, e.g., polyhalogenated-dibenzo-p-dioxins, dibenzofurans, and biphenyls and related compounds, as well as nonessential heavy metals in elemental, ionic or organic forms. Such substances are known to accumulate in the body, and the traditionally employed safety factors (Section 5.2.1) may not be high enough to account for species differences in rates of elimination of such chemicals. Therefore, the TTC approach should not be used for such substances. 

Polyhalogenated dibenzo-p-dioxins, -dibenzofurans, or -biphenyls and similar substances nonessential, heavy metals... 

Waller, C. L. and McKinney, J. D. (1992) Comparative molecular field analysis of polyhalogenated dibenzo-p-dioxins, dibenzofurans, and biphenyls. J. Med. Chem. 35, 3660-3666. 

Halvorson MR, Phillips TD, Safe SH, et al. 1985. Metabolism of aflatoxin BI by rat hepatic microsomes induced by polyhalogenated biphenyl congeners. Appl Environ Microbiol 49(4) 882-886. 

Haung Q, Rusling JF. 1995. Formula reduction potentials and redox chemistry of polyhalogenated biphenyls in a bicontinuous microemulsion. Environ Sci Technol 29(l) 98-103. 

Ruzo LO, Zabik MJ. 1975. Polyhalogenated biphenyls Photolysis of hexabromo and... 

Sepkovic DW, Byme JJ. 1984. Kinetic parameters of L-[ 125I]triiodothyronine degradation in rats pretreated with polyhalogenated biphenyls. Food Chem Toxicol 22(9) 743-747. 

Shepard EC, Phillips TD, Irvin TR. 1984. Aflatoxin BI metabolism in the rat Polyhalogenated biphenyl enhanced conversion to aflatoxin Ml. Xenobiotica 14(9) 741-750. 

Silberhom EM, Glauert HP, Robertson LW. 1990. Carcinogenicity of polyhalogenated biphenyls PCBs and PBBs. Crit Rev Toxicol 20(6) 439-496. 

Electron transfer properties of polyhalogenated biphenyls were investigated by cyclic voltammetry. The primary reduction peak of 4,4 -dichlorobiphenyl, involving replacement of halide with hydrogen in an irreversible ECE- type reaction, are under kinetic control of the initial ET step. Electrochemical transfer coefficients, standard potentials and standard heterogeneous rate constants were also estimated from the voltammetric data230. 

Wagel DJ, Tiernan TO, Taylor ML, Garrett JH, VanNess GF, Solch JG, Harden LA (1989), Che-mosphere 18 177-184. Assessment of ambient air sampling techniques for collecting airborne polyhalogenated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and biphenyls (PCB) ... 

Fish-specific TEFs of halogenated diphenyl ethers have been low also in a rainbow trout early life stage mortality bioassay [85]. Halogenated diphenyl ethers were inactive in this bioassay, whereas polyhalogenated dibenzo-p-dio-xins, dibenzofurans, and biphenyls reduced growth and produced yolk sac edema and craniofacial malformations. PCDEs 71, 77, 102, 118, and 126 and PBDEs 47,85, and 99 were analyzed in this bio assay. 

Representative Chemicals Polybrominated biphenyls (PBBs) are members of the polyhalogenated diaromatic hydrocarbon (PHDH) class of compounds. PBBs are a complex mixture of individual compounds which are brominated with between one and 10 bromines in various combinations of positions to create a total of 209 possible congeners. The 10 positions are numbered 2-6 on one ring and 2 -6 on the other ring. Positions 2, 2, 6, and 6, adjacent to the biphenyl bond are called ortho positions 3, 3, 5, and S, meta positions 4 and 4, para positions. Commercial products were mainly composed of hexa-, octa-, or deca-brominated homologs. Environmental contamination with PBBs is likely to have occurred mainly from two commercial products, FireMaster BP-6 and FireMaster FF-1. The principal components in both of these commercial products were 2,2, 4,4, 5,5 -hexabromobiphenyl or PBB-153 (54-68%) and 2,2, 3,4,4, 5,5 -he-ptabromobiphenyl or PBB-180 (7-27%)... 

Khadikar PV, Singh S, Mandloi D, Joshi S, Bajaj AV. QSAR study on bioconcentration factor (BCF) of polyhalogenated biphenyls using the PI index. Bioorg Med Chem 2003 11 5045-50. 

Polyhalogenated aromatic hydrocarbons TCDD (2,3,7,8-tetrachlorodibenzo p dioxin), PBB (polybromated biphenyls), PCDF (polychlorinated dibenzofuran), PCBs (polychlorinated biphenyls), hexachloro benzene, 2,4- dichlorophenol Appears to correlate with carcinogenic effect. Case studies for PCB and organochlorine pesticides resulted infections associated with immunosuppression... 

James, M.O. and P.J. Fittle. Polyhalogenated biphenyls and phenobarbital evaluation as inducers of drug metabolizing enzymes in the sheepshead, Archosargus probatocephalus. Chem.-Biol. Interact. 36 229-248, 1981. 

Although the last two options are very Important when they occur, as exemplified by the unfortunate cases of thalidomide (1 ) and the polyhalogenated biphenyls (.2) respectively, the great majority of xenoblotlcs undergo enzymic metabolism and/or are eliminated unchanged. In animals. In most cases, metabolism favours the elimination of the compound by enhancing Its polarity... 

Borlakoglu JT, Wilkins JPG. 1993a. Correlations between the molecular structures of polyhalogenated biphenyls and their metabolism by hepatic microsomal monooxygenases. Comp Biochem Physiol 105C(1) 113-117. 

Safe S. 1989a. Polyhalogenated aromatics uptake, disposition and metabolism. In Kimbrough R, Jensen AA, eds. Halogenated biphenyls, terphenyls, naphthalenes, dibenzodioxins and related products. 2nded. Amsterdam, The Netherlands Elsevier Science Publishers, 131-159. 

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