Brominated biphenyls

Bedard DL, H van Dort, KA Deweerd (1998) Brominated biphenyls prime extensive microbial reductive deha-logenation of Arochlor 1260 in Housatonic River sediment. Appl Environ Microbiol 64 1786-1795. 

Other componnds have also been examined as primers for the dechlorination of hexachloro to nonachloro PCB congeners (DeWeerd and Bedard 1999) a nnmber of snbstituted brominated monocyclic aromatic componnds were examined, and 4-bromobenzoate was effective—though less so than 2,6-dibromobiphenyl. In contrast, the chlorobenzoates that are metabolites of aerobic degradation were ineffective. The positive effect of brominated biphenyls in priming the anaerobic dechlorination of CBs has also been encountered in the dechlorination of octachlorodibenzo[l,4] dioxin to the 2,3,7,8 congener indnced by 2-bromodibenzo[l,4]dioxin in the presence of (Albrecht... 

Bedard DL, HM van Dort (1998) Complete reductive dehalogenation of brominated biphenyls by anaerobic microorganisms in sediment. Appl Environ Microbiol 64 940-947. 

Morris PJ, JF Quensen III, JM Tiedje, SA Boyd (1993) An assessment of the reductive debromination of poly-brominated biphenyls in the Pine River reservoir. Environ Sci Technol 27 1580-1586. 

Octa- and higher brominated biphenyls were accumulated by the fish to a small extent only when administered in food. The main compound found in this case was a hexabromobiphenyl, not present in the originally administered mixture of bromobiphenyls (2). 

These observations indicate three possible reasons for the low accumulation of highly brominated biphenyls and benzenes in juvenile Atlantic salmon ... 

Low water solubility, possibly acting in conjunction with low membrane permeability, appears to be the main reason for the lack of accumulation of highly brominated biphenyls and hexabromobenzene from water by juvenile Atlantic salmon. 

PBB-treated rats. Of seven structurally identified PBB components, only 2,2, 4,5,5 -pentabromobiphenyl had a bromine-lrccpara position. Although 2,2, 4,5,5 -pentabromobiphenyl, 2,3, 4,4, 5-pentabromobi-phenyl, and 2,2, 3,4,4, 5 -hexabromobiphenyl have two adjacent unsubstituted carbons, only 2,2, 4,5,5 -pentabromobiphenyl was metabolized. No significant metabolism occurred when the PBB mixture was incubated with microsomes of control rats or MC-induced rats. When 2,2 - and 4,4 -dibromobiphenyl were incubated with liver microsomes of PB-treated rats, only the 2,2 -congener was metabolized. These results suggest that the presence of a free para position is required for the metabolism of brominated biphenyls and that the bromine content of the molecule is less important in determining metabolism than the position of bromines on the biphenyl nucleus. 

Compound/ IIUIUPACIUPAOdktRACIhto." Brominated biphenyls (BB) " Brominated diphenyl ethers (BDE) ... 

Pyrolysis of FireMaster BP-6 in the temperature range of 600 900 °C in the absence of oxygen produced bromobenzenes and brominated biphenyls as key products, but no brominated dioxins and dibenzofurans (Thoma and Hutzinger 1987 Thoma et al. 1987). Thermolysis of Hi re Mast a- BP-6 between 400 and 600 °C in the presence of air produced 23,7,8-tetrabromodibenzofuran in the percent ( 1 %10 g/kg) range (Rappe and Buser 1980). Pyrolysis of FireMaster BP-6 in an open quartz tube at 800 °C produced 0.48 1.49 gZkg2,3,7,8-TCDD equivalent levels of polybrominated dibenzofurans (Zacharewski et al. 

Another process that could release lower levels of brominated biphenyls in the air is the incineration of PBBs. Pyrolysis of hexabromobiphenyl in the absence and presence of air has produced small amounts of lower brominated biphenyls (Thoma and Hutzinger 1987). No data are available on the importance of this source for the release of PBBs in the air during the incineration of PBBs. However, since the vast majority of products containing PBBs are expected to be out of circulation after more than 25 years since the voluntary ban, incineration will not be a significant source of PBBs to air. 

Polybrominated Biphenyls. In air, the two processes that may result in significant degradation or transformation of PBBs are photooxidation by hydroxyl radicals and direct photolysis. The estimated half-life of pentachlorobiphenyl in air due to reaction with hydroxyl radicals is 41.6 83.2 days (Atkinson 1987a). Based on a structure-activity relationship for the estimation of half-lives for the gas-phase reactions of hydroxyl radicals with organic compounds (Atkinson 1987b), the estimated half-lives of hexabromobiphenyl and decabromobiphenyl due to reaction with OH radicals are 182 and 2,448 days, respectively. These half-lives are consistent with the half-life of pentachlorobiphenyl due to reaction with OH radicals. However, the half-lives of brominated biphenyls expected to be present in the particulate phase in the air may be even longer than the estimated half-lives due to gas phase reaction. Therefore, the Iransfonnation of the hexa- and other higher brominated PBBs in the atmosphere due to reaction with OH radicals may not be irrportant. 

Hexa- and other higher brominated biphenyls are expected to be present in the particle-adsorbed state in the atmosphere. These PBBs photolyze in solution and in soil (Hill et al. 1982 Ruzo and Zabik 1975 Trotter 1977). Since PBBs present in surface soil are known to photolyze, particle-sorbed PBBs present in the atmosphere may also undergo photolysis. The importance of the photochemical reaction under sunlight illumination conditions for the degradation/transformation of PBBs in air cannot be evaluated due the lack of information. 

Polybrominated Biphenyls. The photolytic degradation of PBBs in solution has been the subject of several studies. Available data in the literature indicate that brominated biphenyls photodegrade by reduction in solvents capable of proton transfer with the formation of lower brominated biphenyls. For example, the irradiation of FireMaster BP-6 and 2,2, 4,4, 5,5 -hexabromobiphenyl in methanol at wavelengths >286 nm produced mainly penta- and tetrabromobiphenyl (Ruzo and Zabik 1975). FireMaster BP-6 photolyzed7 times faster than its chlorinated counterpart, 2,2, 4,4, 5,5 -hexachloro-biphenyl (Ruzo and Zabik 1975). Although an earlier study tentatively identified dimethoxy tetrabromobiphenyl as a photolysis product of FireMaster BP-6 (Ruzo and Zabik 1975), later work did not detect this compound (Ruzo et al. 1976). Earlier studies indicated that the debromination usually occurs with the stepwise preferential loss of bromine from the ortho and para positions of the biphenyl ring (i.e., 2, 2, 6, and 6 positions) (De Kok et al. 1977 Ruzo and Zabik 1975 Ruzo et al. 1976 Trotter 1977). Thus, the photolysis of 2,2, 4,4, 5,5 -hexachlorobiphenyl, the major component of FireMaster BP-6, would be expected to produce 23, 4,4, 5-pentabromobiphenyl and subsequently... 

Polybrominated Biphenyls. Soil samples from the bagging and loading areas of the Michigan Chemical Corporation plant in St. Louis, Michigan, contained PBBs at concentrations of 3,500 and 2,500 mg/kg, respectively (Di Carlo et al. 1978). PBBs (mostly decabromobiphenyl, but some lower brominated biphenyls down to hexabromobiphenyl) in soil near the Hexcel Chemical Corporation plant in New Jersey and the White Chemical Company plant in New Jersey ranged from 40 to 4.6 mg/kg and from... 

Polybrominated Biphenyls. PBBs do not readily translocate from soil to plants via root uptake (Jacobs et al. 1976, 1978). Therefore, PBBs may not bioconcentrate in plants. However, plant uptake data are limited, audit will be helpful to develop additional plant uptake data. Brominated biphenyls with bromine substitution 6 or less will bioconcentrate in aquatic organisms (Gobas et al. 1989 Norris et al. 1973 Opperhuizen et al. 1985 Zitko 1979 Zitko and Hutzinger 1976). PBBs are preferentially stored in the adipose tissue of animals (Kimbrough 1987). Although PBBs have been detected in fish-eating birds... 

Farrell TJ. 1980. Glass capillary gas chromatography of chlorinated dibenzofurans, chlorinated anisoles, and brominated biphenyls. J Chromatogr Sci 18 10-17. 

McCormack KM, Hook JB. 1982. Effects of lactation and nursing on tissue concentrations of poly brominated biphenyls and on microsomal enzyme activity in mammary gland and liver in maternal rats. EnvironRes 27 110-117. 

Waritz RJ, Aflosmis JG, Culik R, et al. 1977. Toxicological evaluations of some brominated biphenyls. Am Ind Hyg Assoc J 38 307-320. 

Bedard, D. L. Van Dort, H. M. (1992). Brominated biphenyls can stimulate reductive dechlorination of endogenous Aroclor 1260 in methanogenic sediment slurries. In Abstracts of the General Meeting of the American Society for Microbiology. New Orleans, Louisiana Q-26, p. 339. 

Ah locus A gene(s) controlling the trait of responsiveness for induction of enzymes by aromatic hydrocarbons. In addition to aromatic hydrocarbons such as the polycyclics, the chlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls, as well as the brominated biphenyls, are involved. This trait, originally defined by studies of induction of hepatic aryl hydrocarbon hydroxylase activity following 3-methylcholanthrene treatment, is inherited by simple autosomal dominance in crosses and backcrosses between C57BL/6 (Ah-responsive) and DBA/2 (Ah-nonresponsive) mice. 

In follow-up experiments, Gobas et al. (1989) found that brominated biphenyls which have minimal internal cross sections somewhat greater than 0.95 nm were available for uptake in fish via the gills. In addition, Muir et al. (1986) and Muir and Yarechewski (1988) reported that octachlorodibenzo-p-dioxin, which has a minimal internal cross section greater than 0.95 nm, was present in internal tissues of trout exposed under field conditions. 

Dysidea herbacea, which sequesters brominated biphenyl ethers synthesized by symbiotic bacteria, concentrates these secondary metabolites in their ectosomal area.89... 

International Agency for Research on Cancer, Polychlorinated Biphenyls and Poly-brominated Biphenyls, Vol. 18 October, 1978. 

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