Characteristics and structures of PCBs
Polychlorinated biphenyls, better known by the abbreviation PCB, are a family of organic chemical compounds.
They are often known by their trade names Pyralene, Arochlor or Askarel.
They are, more precisely, biphenyl molecules, that is to say two benzene rings linked together, in which 1 to 10 chlorine atoms replace the hydrogen atoms. There are thus 209 possible combinations, according to the distribution of the chlorine atoms on the biphenyl molecule.
According to their chlorine content, polychlorinated biphenyls are more or less viscous liquids or resinous, insoluble in water, colorless or yellowish, with strong aromatic odor.
History and uses of PCBs
PCBs were manufactured industrially from 1930 and were massively used until the 1980s. Their production has been stopped since 1983 in most countries. It is estimated that about 1.5 to 2 million tonnes of PCBs have been produced worldwide.
PCBs have been used in a multitude of applications, many of which are still in use today. They are found as dielectric fluid in electrical transformers and capacitors, as lubricants in turbines and pumps or as components of oils, adhesives, paints and carbonless papers.
Indeed, polychlorinated biphenyls are characterized by good chemical stability, relative flammability (up to 1000 ° C) and have excellent dielectric properties (they do not conduct electrical current).
PCB impacts on health and the environment
Due to the presence of chlorine atoms in their structure, PCBs are not very biodegradable, they persist after release into the environment and can be transported over long distances.
Because of their oleophilic (fat-soluble) property, PCBs accumulate in fatty tissues throughout the food chain, such that links at the ends of food chains, such as carnivores, fish Predatory fish or humans are subject to strong bioaccumulation.
PCBs are well resorbed by the digestive tract, but also by the skin and lungs, they are distributed quickly in the body and enriched in adipose tissue. The absorption of large amounts leads to acute diseases of the skin (chlorinated acne, pigmentations of the skin and nails, hair loss), cause damage to the liver, spleen and kidneys and weaken the immune system. In addition, PCBs are suspected of being carcinogenic to humans.
In the presence of oxygen, the combustion of PCBs produces very toxic compounds belonging to the family of dioxins and furans.