Polychlorinated biphenyls Monsanto

Polychlorinated biphenyls (PCBs) were manufactured by catalytic chlorination of biphenyl to produce complex mixtures, each containing 60-90 different PCB molecular species or congeners (see Chaps. 1 and 4). In the United States, PCB mixtures were manufactured by Monsanto under the trade name Aroclor and were widely used as dielectric fluids in capacitors and transformers from 1929 to 1978. PCBs are widespread contaminants of aquatic sediments and continue to be a focus of environmental concern because they tend to accumulate in biota and are potentially toxic. The following sections show the most effective bioremediation techniques applied to various PCB contaminated environments ... 

Polychlorinated biphenyls (PCBs), known by their trade marks of Arochlor (Monsanto U.S.), Phenochlor (in France), and Clophen (in Germany) are chemically similar to the chlorinated insecticides. Although not used for this purpose, their existence and persistence in the environment is well established. 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 this application. They have been made by Monsanto since 1930 and were first discovered as a pollutant in 1966. U.S. production peaked at 72 million lb in 1970 but in 1975 it was down to 40 million Ib/yr because in 1971 Monsanto voluntarily adopted the policy of selling PCBs only for electrical systems. At least 105 PCBs are present in the environment. 

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. 

Monsanto Chemical Company. 1985. Monsanto material safety data Polychlorinated biphenyls (PCBs). St. Louis, MO Monsanto Company. 

Polychlorinated biphenyls (PCB), are a family of toxic, oily, non-flammable chemicals. They are man-made products and were first commercialised in 1929 (by Monsanto). They were mainly used in electrical equipment (e.g., transformers and capacitors), as heat transfer and hydraulic fluids, and as plasticisers from World War I until recently, mainly due to their exceptional thermal and chemical stabilities. Although their production in the USA was stopped in 1977 (they were banned worldwide), some production still continues, and it is believed that large quantities of PCB may still be present in some old transformer and capacitor systems. PCB are certainly still present in the USA in some electrical equipment and are frequently found at toxic waste sites and in contaminated sediments worldwide. The sealants based on polysulfhide polymers that were used in buildings some 20-40 years ago contained PCB, which has been shown still to exist at alarming levels in some houses in Sweden, [24]. 

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). 

Aroclors, n—commercial mixtures of polychlorinated biphenyl congeners marketed and trademarked by Monsanto prior to 1977. 

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). 

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