Biphenyl and PCBs

CHEMICAL NAME = biphenyl CAS NUMBER = 92-52-4 MOLECULAR FORMULA = C12H10 MOLAR MASS = 154.2 g/mol COMPOSITION = C(93.5°/o) H(6.5%) 

Biphenyl was once used extensively for the production of polychlorinated biphenyls (PCBs) before their production was banned in the United States in 1979. PCBs are formed by direct substitution of hydrogen atoms in biphenyl with chlorine using chlorine gas under pressure with a ferric chloride (FeCl3) catalyst. There are 209 possible PCB compounds referred to as congeners. PCBs were discovered in 1865 as a by-product of coal tar and first synthesized in 1881. Commercial production of PCBs, originally called chlorinated diphenyls, began in 1929 by the Swann Chemical Company located in Anniston, Alabama. Swann was taken over by Monsanto in 1935. 

PCBs are synthetic chemicals that exist as oils or waxy substances they do not occur naturally. They were once used in many products including hydraulic fluids, pigments, inks, plasticizers, lubricants, and heat transfer fluids, but their primary use was as a dielectric fluid in electrical equipment. Because of their high thermal stability, chemical stability, and electrical insulating properties, PCB fluids were used extensively in transformers, fluorescent light 

Production of PCBs increased between 1930 and 1970, with a large increase in production after World War II. It is estimated that 650,000 tons of PCBs were produced in the United States during this 40-year period, with a peak of 42,000 tons in 1970. Global production was approximately twice that of the United States during this same period. Another 400,000 tons have been produced outside the United States after their production was banned in this country in 1979. Health problems started to appear in PCB plant workers soon after their commercialization. The first problem observed among PCB workers was chloracne, a condition resulting in skin lesions associated with overexposure to chlorine compounds. 

As PCB production increased, more concerns were raised about the health and environmental effects of PCBs, which entered the environment through leakage, production processes, and improper disposal. The persistence and lipophilicity of PCBs resulted in its biomagnification in the environment (see DDT). Problems associated with PCB contamination in wildlife include deformities, tumors, disruption in the endocrine and reproduction systems, and death. Human exposure to PCBs occurs through environmental and occupational routes. The primary exposure 

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Thomas DR, Carswell KS, Georgiou G (1992) Mineralization of biphenyl and PCBs by the white rot fungus Phanerochaete chrysosporium. Biotechnol Bioeng 40 1395-1402... 

The ubiquitous occurrence of bacteria, which can utilize biphenyl as a sole source of carbon and energy, has been reported. Several species of Gram-negative and Gram-positive bacteria have been shown to degrade biphenyl and PCBs. The main pathway for biphenyl catabolism is outlined in Figure 3 [58-66]. 

Figure 3. Catabolic pathway for degradation of biphenyl and PCB by bacteria. I, biphenyl II, 2,3-dihydroxy-4-phenylhexa-2,4-diene (2,3-dihydrodiol) HI, 2,3-dihydro] biphenyl IV, 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (meto-cleavage compound) V, benzoic add.

The widespread use of biphenyl and methyl-substituted biphenyls as dye carriers (qv) in the textile industry has given rise to significant environmental concern because of the amount released to the environment in wastewater effluent. Although biphenyl and simple alkylbiphenyls are themselves biodegradable (48—50), the prospect of their conversion by chlorination to PCBs in the course of wastewater treatment has been a subject of environmental focus (51—53). Despite the fact that the lower chlorinated biphenyls are also fairly biodegradable (49,54,55) continued environmental concern has resulted in decreased use of biphenyl as a dye carrier (see Dyes, environmental chemistry). 

It is known that the brain is one of the most sensitive sites of action of steroids in utero, and recently there have been suggestions that EDs may affect normal brain development and behaviour. For example, it has been alleged that in utero exposure to polychlorinated biphenyl compounds (PCBs) resulted in adverse effects on neurologic and intellectual function (memory and attention) in young children born to women who had eaten PCB contaminated fish in the USA." It has also been speculated that exposure to environmental pollutants with steroidal activity may be infinencing human sexual development and sexually controlled behavioiir." ... 

EC Directive on the disposal of polychlonnated biphenyls and polychlorinated terphenyls (PCB/PCTj... 

Wu Q, DL Bedard, J Wiegel (1997a) Effect of incubation temperature on the route of microbial reductive dechlorination of 2,3,4,6-tetrachlorobiphenyl in polychlorinated biphenyl (PCB)-contaminated and PCB-free freshwater sediments. Appl Environ Microbiol 63 2836-2843. 

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. 

Fatty food - Determination of pesticides and polychlorinated biphenyls (PCBs) - Part 1 General considerations Part 2 Extraction of fat, pesticides and PCBs and determination of fat content... 

Chou, S.F.J., Griffin, R.A. (1987) Solubility and soil mobility of polychlorinated biphenyls. In PCBs and the Environment. Waid, J.S., Editor, CRC Press, Inc., Boca Raton, Florida, pp. 101-120. 

Murk, A.J., J.H. J van den Berg, J.H. Koeman, and A. Brouwer. 1991. The toxicity of tetrachlorobenzyltoluenes (Ugilec 141) and polychlorinated biphenyls (Aroclor 1254 and PCB-77) compared in Ah-responsive and Ah-nonresponsive mice. Environ. Pollut. 72 57-67. 

Investigations have shown that plants on thermal treatment of solid domestic waste represent the source of polychlorinated dibenzodioxins and biphenyls. In this connection, it is necessary to conduct further investigations of their emission and determination of all the range of PCDD, PCDF and PCB... 

Goerlitz and Law [41] determined chlorinated insecticides in sediment and bottom material samples which also contained PCBs by extracting the sample with acetone and hexane. The combined extracts were passed down an alumina column. The first fraction (containing most of the insecticides and some polychlorinated biphenyls and polychlorinated naphthalenes) is eluted with hexane and treated with mercury to precipitate sulphur. If the polychlorinated hydrocarbons interfere with the subsequent gas chromatographic analysis, further purification on a silica gel column is necessary. 

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