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Because of PCBs' environmental toxicity and classification as a persistent organic pollutant, PCB production was banned by the United States Congress in 1979 and by the Stockholm Convention on Persistent Organic Pollutants in 2001. Environmental Protection Agency (EPA), PCBs cause cancer in animals and are probable human carcinogens.
The International Research Agency on Cancer (IRAC), rendered PCBs as definite carcinogens in humans. Many rivers and buildings including schools, parks, and other sites are contaminated with PCBs, and there have been contaminations of food supplies with the toxins.
Another estimate put the total global production of PCBs on the order of 1.5 million tons.
The United States was the single largest producer with over 600,000 tons produced between 19.
An exception is Aroclor 1016, which also has 12 carbon atoms, but has 42% chlorine by mass.
Aroclor 1016 was prepared by the fractional distillation of Aroclor 1242, which excluded the higher boiling (i.e., more highly chlorinated) congeners.
As the degree of chlorination increases, melting point and lipophilicity increase, and vapour pressure and water solubility decrease.
It is unlikely that a full inventory of global PCB production will ever be accurately tallied, as there were factories in Poland, East Germany, and Austria that produced unknown amounts of PCBs.Different Aroclors were used at different times and for different applications.In electrical equipment manufacturing in the USA, Aroclor 1260 and Aroclor 1254 were the main mixtures used before 1950; Aroclor 1242 was the main mixture used in the 1950s and 1960s until it was phased out in 1971 and replaced by Aroclor 1016.The atmosphere serves as the primary route for global transport of PCBs, particularly for those congeners with one to four chlorine atoms.Atmospheric concentrations of PCBs tend to be lowest in rural areas, where they are typically in the picogram per cubic meter range, higher in suburban and urban areas, and highest in city centres, where they can reach 1 ng/m³ or more.
In PCBs, some of the hydrogen atoms in biphenyl are replaced by chlorine atoms.