Polychlorinated biphenyls,

Polychlorinated biphenyls (PCBs, Arochlor , Phenochlor , and Clophen ) are chemically similar to the chlorinated insecticides. 

Polychlorinated biphenyls are manufactured by chlorination of biphenyl. The conditions determine the degree of chlorination. 

They were used to make more flexible and flame-retardant plastics and are still used as insulating fluids in electrical transformers since there is no substitute in the application. Their existence and persistence in the environment is well established, and they are classed as a pollutant. 

Polychlorinated biphenyls (PCBs) have been used in the manufacturing of electrical transformers. They are highly persistent in the environment. Rodent tests have suggested that PCBs are carcinogenic and the U.S. government strongly regulates their production (Shelton, 1989). 

Eisler, R. 1986. Polychlorinated biphenyl hazards to fish, wildlife, and invertebrates a synoptic review. U.S. Fish Wildl. Serv. Biol. Rep. 85(1.7), 72 pp. 

Eisler, R. 2000. Polychlorinated biphenyls. Pages 1237-1341 in Handbook of Chemical RiskAssessment Health Hazards to Humans, Plants, and Animals. Volume 2, Organics. Lewis Publishers, Boca Raton, Florida. 

Polychlorinated biphenyls have very high chemical, thermal, and biological stability low vapor pressure and high dielectric constants. These properties have led to the use of PCBs as coolant-insulation fluids in transformers and capacitors for the impregnation of cotton and asbestos as plasticizers and as additives to some epoxy paints. The same properties that made extraordinarily stable PCBs so useful also contributed to the widespread dispersion and accumulation of these substances in the environment. By regulations issued in the United States under the authority of the Toxic Substances Control Act passed in 1976, the manufacture of PCBs was discontinued in the United States, and their uses and disposal were strictly controlled. Some degree of biodegradation of PCBs in the environment does occur. 

FIGURE 4.13 General formula of polychlorinated biphenyls (left, where X may range from 1 to 10) and a specific 5-chlorine congener (right). 

Substitutes for PCBs for electrical applications have been developed. Disposal of PCBs from discarded electrical equipment and other sources have caused problems, particularly since PCBs can survive ordinary incineration by escaping as vapors through the smokestack. However, they can be destroyed by special incineration processes. 

Classes of Emerging Water Contaminants of Concern as Pollutants Contaminant 

Discarded into wastewaters or from human wastes in sewage From human wastes in sewage From human wastes in sewage Synthetic compounds that disrupt endocrine function A wide variety of inorganic and organic substances in the 1-100 nm size range with many developing uses 

Polychlorinated biphenyls (PCBs) are a group of chlorinated aromatic compounds with widespread applications. PCBs have been prepared synthetically since 1929 and most information on their manufacture under trade names and general characteristics are available from trade publications. The Monsanto Chemical Company, the sole manufacturer in the USA, has provided most information on their preparation and properties (Monsanto, 1972, 1974). 

All Aroclor products (Aroclor is the trade name of Monsanto s PCB) are characterized by a four-digit number. The first two digits stand for the type of molecule 12 refers to chlorinated biphenyls and 54 to chlorinated ter-phenyls, though some 54 Aroclors could be a mixture of ter- and biphenyls. Aroclors 25- and 44- are mixtures of PCBs and polychlorinated terphenyls (75% and 60% PCB, respectively). The last two digits of the formula represent the percent weight of chlorine (Table 9.1). 

Theoretically, 209 different chlorobiphenyls can exist based on the possible distribution of Cl atoms in the two rings of the biphenyl. However, 

PCBs were first produced in 1929, in USA annual production and use increased steadily until 1970, and became effectively worldwide. Uses can be classified into 3 types  

Following the growing number of observations of widespread environmental occurrence Monsanto in 1971 ceased the sale of PCB for all applications except electrical and some hydraulic this voluntary ban was followed by other producers, and by 1977 worldwide manufacture for any purposes had virtually ceased. 

Until then, entry of PCB to the environment had been by the following routes (a) Completely dispersive losses - all material used in paints, inks, adhesives, cutting oils, etc must be assumed to have been lost, via widely scattered sources, either direct to waterways, or indirectly from land disposal. 

Total cumulative world production of PCB has been estimated at about 

000 tonnes peak production rate was about 70,000 tpa in 1970. Of these totals, approximately 60% went into closed electrical uses, 15% to nominally closed, and 25% to dispersive uses. It may be deduced therefore that some 40%, that is 

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Ei ivironrr lent Absence of toxic compounds such as polychlorinated biphenyls (PCB s)... 

The aim of the first example is to look for polychlorinated biphenyls (PCB) for which C-NMR spectra, measured in deuterochloroform, as well as the partition coefficients between 1-octanol and water arc known. Since it is not reliable to per-... 

Figure 5-16. Structure editor of the CrossFire ComiTiander V6, showing the definition ofan atom list (consisting of hydrogen and chlorine atoms) for polychlorinated biphenyls.

The performance of SCWO for waste treatment has been demonstrated (15,16). In these studies, a broad number of refractory materials such as chlorinated solvents, polychlorinated biphenyls (PCBs), and pesticides were studied as a function of process parameters (17). The success of these early studies led to pilot studies which showed that chlorinated hydrocarbons, including 1,1,1-trichloroethane /7/-T5-6y,(9-chlorotoluene [95-49-8] and hexachlorocyclohexane, could be destroyed to greater than 99.99997, 99.998, and 99.9993%, respectively. In addition, no traces of organic material could be detected in the gaseous phase, which consisted of carbon dioxide and unreacted oxygen. The pilot unit had a capacity of 3 L/min of Hquid effluent and was operated for a maximum of 24 h. 

Solvent extraction followed by gas chromatographic analysis is used to determine paraffin wax antioxidants (qv), ie, butylated hydroxyanisole and butylated hydroxytoluene and other volatile materials. Trace amounts of chlorinated organic compounds, eg, polychlorinated biphenyls, can be deterrnined by using a gas chromatograph with an electron-capture detector (22). 

TSCA also addresses the problem of polychlorinated biphenyls (PCBs) and chlorinated fluorocarbons (CECs). EPA has developed regulations on the cleanup, handling, and disposal of PCBs. The manufacture and use of CECs has been banned for all but essential uses, in accordance with the Montreal Agreement, an international treaty on worldwide use of CECs. 

Common examples of compounds that are amenable to carbon adsorption are aromatics (benzene, toluene) and chlorinated organics (trichloroethylene, trichloroethane [71-55-6, 75 -(9(9-j5y, tetrachloroethylene, polychlorinated biphenyls (PCBs), DDT /T(9-77-77, pentachlorophenol [87-86-5J. Compounds that are not adsorbed effectively by carbon include ethanol [64-17-5], diethylene glycol [111-46-6], and numerous amines (butylamine [109-73-9, 13952-84-6, 75-64-9], triethanolamine [102-71-6], cyclohexylamine [108-91-8], hexamethylenediamine [108-91-8] (1). Wastewater concentrations that are suitable for carbon adsorption are generally less than 5000 mg/L. 

In earlier editions of the Eniyclopedia there have been articles covering the properties, manufacture, capacities, etc, of polychlorinated biphenyls (PCBs), chlorinated naphthalenes, benzene hexachloride, and chlorinated derivatives of cyclopentadiene. These materials are no longer in commercial use because of their toxicity. However, they stiU impact on the chemical industry because of residual environmental problems. Their toxicity and environmental impact are discussed (see Cm.OROCARBONSANDCm.OROHYDROCARBONS, TOXIC aromatics). 

BTEX Benzene, toluene, xylene PCB Polychlorinated biphenyl... 

SW-846, is used to measure emissions of semivolatile principal organic constituents. Method 0010 is designed to determine destruction and removal efficiency (DRE) of POHCs from incineration systems. The method involves a modification of the EPA Method 5 sampling train and may be used to determine particulate emission rates from stationary sources. The method is applied to semivolatile compounds, including polychlorinated biphenyls (PCBs), chlorinated dibenzodioxins and dibenzofurans, polycyclic organic matter, and other semivolatile organic compounds. 

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