page_title: Polychlorinated biphenyl
section_title: History
hierarchical_section_title: Polychlorinated biphenyl / History
caption_attribution_description: English: Railroad signal power supply transformer dating from the 1930's at CP-SLOPE interlocking, west of Altoona with a warning label indicating that it contains PCBs.
context_page_description: A polychlorinated biphenyl is an organic chlorine compound with the formula C₁₂H10−ₓClₓ. Polychlorinated biphenyls were once widely deployed as dielectric and coolant fluids in electrical apparatus, carbonless copy paper and in heat transfer fluids.
  Because of their longevity, PCBs are still widely in use, even though their manufacture has declined drastically since the 1960s, when a host of problems were identified. With the discovery of PCBs' environmental toxicity, and classification as persistent organic pollutants, their production was banned by United States federal law in 1978, and by the Stockholm Convention on Persistent Organic Pollutants in 2001. The International Agency for Research on Cancer, rendered PCBs as definite carcinogens in humans. According to the U.S. Environmental Protection Agency, PCBs cause cancer in animals and are probable human carcinogens. Many rivers and buildings, including schools, parks, and other sites, are contaminated with PCBs and there has been contamination of food supplies with the substances.
  Some PCBs share a structural similarity and toxic mode of action with dioxins.
context_section_description: In 1865 the first "PCB-like" chemical was discovered, and was found to be a byproduct of coal tar. Years later in 1881, German chemists synthesized the first PCB in a laboratory. Between then and 1914, large amounts of PCBs were released into the environment, to the extent that there are still measurable amounts of PCBs in feathers of birds currently held in museums.
  In 1935, Monsanto Chemical Company (now Solutia Inc) took over commercial production of PCBs from Swann Chemical Company which had begun in 1929. PCBs, originally termed "chlorinated diphenyls", were commercially produced as mixtures of isomers at different degrees of chlorination. The electric industry used PCBs as a non-flammable replacement for mineral oil to cool and insulate industrial transformers and capacitors. PCBs were also commonly used as heat stabilizer in cables and electronic components to enhance the heat and fire resistance of PVC.
  In the 1930s, the toxicity associated with PCBs and other chlorinated hydrocarbons, including polychlorinated naphthalenes, was recognized because of a variety of industrial incidents. Between 1936 and 1937, there were several medical cases and papers released on the possible link between PCBs and its detrimental health effects. In 1936 a U.S. Public health Service official described the wife and child of a worker from the Monsanto Industrial Chemical Company who exhibited blackheads and pustules on their skin. The official attributed these symptoms to contact with the worker's clothing after he returned from work. In 1937, a conference about the hazards was organized at Harvard School of Public Health, and a number of publications referring to the toxicity of various chlorinated hydrocarbons were published before 1940.
  In 1947 Robert Brown reminded chemists that Arochlors were "objectionably toxic. Thus the maximum permissible concentration for an 8-hr. day is 1 mg/m³ of air. They also produce a serious and disfiguring dermatitis".
  In 1954 Japan, Kanegafuchi Chemical Co. Ltd. (Kaneka Corporation) first produced PCBs, and continued until 1972.
  Through the 1960s Monsanto Chemical Company knew increasingly more about PCBs' harmful effects on humans and the environment, per internal leaked documents released in 2002, yet PCB manufacture and use continued with few restraints until the 1970s.
  In 1966, PCBs were determined by Swedish chemist Sören Jensen to be an environmental contaminant. Jensen, according to a 1994 article in Sierra, named chemicals PCBs, which previously, had simply been called "phenols" or referred to by various trade names, such as Aroclor, Kanechlor, Pyrenol, Chlorinol and others. In 1972, PCB production plants existed in Austria, West Germany, France, the UK, Italy, Japan, Spain, the USSR and the US.
  In the early 1970s, Ward B. Stone of the New York State Department of Environmental Conservation (NYSDEC) first published his findings that PCBs were leaking from transformers and had contaminated the soil at the bottom of utility poles.
  There have been allegations that Industrial Bio-Test Laboratories engaged in data falsification in testing relating to PCBs. In 2003, Monsanto and Solutia Inc., a Monsanto corporate spinoff, reached a US$700 million settlement with the residents of West Anniston, Alabama who had been affected by the manufacturing and dumping of PCBs. In a trial lasting six weeks, the jury found that "Monsanto had engaged in outrageous behavior, and held the corporations and its corporate successors liable on all six counts it considered – including negligence, nuisance, wantonness and suppression of the truth."
  Existing products containing PCBs which are "totally enclosed uses" such as insulating fluids in transformers and capacitors, vacuum pump fluids, and hydraulic fluid, are allowed to remain in use. The public, legal, and scientific concerns about PCBs arose from research indicating they are likely carcinogens having the potential to adversely impact the environment and, therefore, undesirable as commercial products. Despite active research spanning five decades, extensive regul
caption: Old power transformers are a major source of PCBs. Even units not originally filled with PCB may be contaminated, since PCB and oil mix freely and any given transformer may have been refilled from hoses or tanks also used with PCBs.
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