Polychlorinated Biphenyls are manmade organic chemical compounds. They are synthetic chlorinated hydrocarbons consisting of Carbon, Hydrogen and Chlorine atoms. PCBs have a lot of commercial and industrial applications; however their production was banned in 1979, due to their toxicity levels and health risks. Polychlorinated Biphenyls have a wide range of uses due to their desirable chemical properties. PCBs were used as coolants, plasticizers, hydraulic fluids, fluorescent light ballasts, etc. PCBs in addition took part in transformers and capacitors, oil-based paint, carbonless copy paper, cabal and thermal insulation; they also appear in electrical equipment and devices such as switches and voltage regulators (EPA). PCBs have a range of properties that vary slightly from type to type, usually PCBs are a very stable and rather inert compounds owed to their chemical make-up and structure. PCBs are non-flammable and have high electrical resistance; they are also very heat resistant and have a high boiling point in addition to being grate insulators (Environmental Chemistry). .
PCBs were first discovered in 1865 as a byproduct of coal tar; however PCBs weren't manufactured until 1929 and were banned fifty years later in the US. PCBs were marketed worldwide under the brand names Aroclor, Askarel, and Therminol. In 1970 the PCBs market reached its peak with a total of 35million kg from 12 types of Aroclors with chlorine levels ranging from 21 to 68%. The production of Polychlorinated Biphenyls involves the chlorination of biphenyl in the presence of a catalyst, such as iron filings. The degree of chlorination is determined by the time biphenyl spent in the reactor averaging from 12-36 hours. Polychlorinated dibenzofurans (PCDFs) has contaminated in small amounts the Aroclor in the process of production. In the US 99% of PCBs were manufactured by Monsanto Chemical Company who produced Aroclors 1221, 1232, 1242, 1248, 1254, 1260, 1262, and 1268, but stopped in 1971 and manufactured only Aroclor 1016, 1242, 1254 in addition to small amounts of 1221.
