School of Biological Sciences
Natural Resources: depletion, pollution and toxicology
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School of Biological Sciences |
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Natural Resources: depletion, pollution and toxicology[ BIOL202 Home | Aquabiology at Liverpool ] |
PCBs or polychlorinated biphenyls are a group of chemicals consisting of 209 individual compounds. PCBs were widely used as a fire preventive and insulator in the manufacture of transformers and capacitors because of their ability to withstand exceptionally high temperatures. They are complex mixtures of chemicals (100 – 130 in the average environmental sample) which were used (and subsequently released as ‘technical mixtures’ named in various ways which indicate how chlorinated they are : Arochlor 1042, Arochlor 1254, Arochlor 1262). Each component has its own chemical and toxicological properties. They are difficult and expensive to unambiguously analyse.
PCBs were introduced in 1930 as a non-flammable, chemically inert fluid. There use increased for approximately 40 yrs. Unfortunately, their properties of chemical and thermal stability which gave them industrial utility made them very refractory in the environment so that they became ubiquitous in the environment. Since they are toxic and potentially carcinogenic with the ability to bioaccumulate and magnify up food chains they have caused considerable environmental problems. They were actually discovered by Jensen in 1966 as an interference during the analysis of DDT in Swedish environmental samples.
PCBs were banned in new uses by the USEPA in 1979, with a complete ban in 1984. They are classified as a probable human carcinogen by numerous national and international health-protective organizations, such as the EPA, The Agency for Toxic Substances and Disease Registry (an arm of the U.S Public Health Service) and the World Health Organization. Research also links PCB exposure to developmental problems.
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