PCBs stands for Polychlorinated Biphenyls. The name refers to any one, or any combination of 209 specific chemicals that are similar in structure. PCBs are extremely persistent. They last for many years because they do not break down easily on their own and they are difficult to destroy.

PCBs were first manufactured in 1929. For several decades, they were used widely as ingredients in many industrial materials, such as sealing and caulking compounds, cutting oils, inks and paint additives. PCBs were also used to make coolants and lubricants for certain kinds of electrical equipment, such as transformers and capacitors.

Attention began to focus on potential hazards linked to the use and disposal of PCBs, when the presence of  PCBs was detected in the Great Lakes for the first time in 1966. By 1977, concern over the impact of PCBs on the environment led to a North American ban on manufacturing and importing PCBs. The ban did not cover PCBs that were already in use in electrical applications. These are being phased out now, and the federal government has set strict regulations for the handling, storage and disposal of PCBs.