Polybrominated biphenyls, contamination production

Polybrominated Biphenyls. The production of PBBs in the United States ceased in 1979 (lARC 1986). In the past, PBBs were released to the environment during the manufacture of these compounds and disposal of commercial and consumer products containing these compounds (Hesse and Powers 1978 Neufeld et al. 1977). One of the significant sources of environmental contamination occurred as a result of the accidental mixup ofFireMaster BP-6 with cattle food in a number of farms in the lower peninsula in Michigan (see Section 3.2 for additional details concerning this incident). By June 1975, 412 farms had been quarantined. Disposal of contaminated feed, animal carcasses (poultry, cattle, swine), and... 

Anderson HA, Wolff MS, Lilis R, et al. 1979. Symptoms and clinical abnormalities following ingestion of polybrominated-biphenyl-contaminated food products. Arm N Y Acad Sci 320 684-702. 

The principal source of pollution by polybrominated biphenyls (PBBs) has been the commercial mixture Firemaster, which was produced in the United States between 1970 and 1974. Production was discontinued in 1974 following a severe pollution incident in Michigan, when Firemaster was accidentally mixed with cattle feed on a farm. In due course, PBBs entered the human food chain via contaminated animal products. Substantial residues were found in humans from the area, and were snbse-quently found to be highly persistent. 

The structural range of industrially important representatives of these groups is enormous, and includes chlorobenzenes (solvents), polychlorinated biphenyls (PCBs) (hydraulic and insulating fluids), and polybrominated biphenyls and diphenyl ethers (flame retardants). There is widespread concern over both the persistence and the potential toxicity of all these compounds, and sites that have become contaminated during their production represent a threat both to the environment and to human health. Pathways for the aerobic bacterial degradation of chlorobenzenes and chlorobiphe-nyls, and their brominated analogs have been discussed in Chapter 9, Part 1. 

Polybrominated Biphenyls. The important former sources of PBBs in soil are manufacturing operations, disposal of PBB-containing finished products, and agricultural operations contaminated in the original episode in 1973 1974. The concentrations of PBBs in soils from bagging and loading areas of the Michigan Chemical Corporation were 3,500 and 2,500 mg/kg, respectively (Di Carlo et al. 1978). 

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%)... 

Debromination of polybrominated biphenyls has been observed in cultures obtained from sediments contaminated with the corresponding chlorobiphenyls (Morris et al. 1992). Complete debromination has been observed in sediment slurries supplemented with malate (Bedard and van Dort 1998) biphenyl was the end product from all congeners, and the acclimation time for 2- and 4-mono-bromo and the 2,4-, 2,5-, and 2,6-dibromo compounds was much less than for the corresponding chloro compounds. All of the intermediates were isolated and this enabled a complete sequence of debromination to be established. 

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