Polychlorinated biphenyls (PCBs) are a family of 209 congeners of structurally similar organic chemicals, ranging from oily liquids to waxy solids. There are 12 PCBs that are dioxin-like and can similarly be toxic and non-toxic. One dioxin-like PCB is 3,4,4',5-Tetrachlorobiphenyl. PCBs are synthetic and produced either as a singular congener, as a homogeneous group or as a mixture. They are non-flammable, stable, have a high boiling point and exhibit electrical insulating properties. As such, PCBs have been used as coolants and lubricants in transformers and other electrical equipment, as hydraulic fluids, and as plasticizers, pigments, dyes and carbonless copy paper ink. They are also generated and released into the environment as waste byproducts of chemical manufacturing and incineration.