PCB polychlorinated biphenyls

　　Polychlorinated biphenyls were artificially synthesized organic compounds used commercially in North America from 1929 to the late 1970s. Although Canada did not process and produce this chemical substance, it has been widely used in electrical equipment insulation, heat exchangers, water systems, and other special applications.

　　It took decades for people to realize the global environmental pollution caused by polychlorinated biphenyls, which are mixtures of various chlorinated biphenyls and pose great harm to human health. The Canadian government once took measures to try to eliminate PCBs, but in 1977, illegal imports, processing and sales of PCBs occurred in Canada, and in 1985, PCBs were illegally released to the natural environment. The Canadian Constitution allows PCB equipment owners to continue to use PCBs until the life of the equipment. Since 1988, provincial governments in Canada have only begun to regulate the storage, transportation, and destruction of PCBs.