Polychlorinated biphenyls (PCBs), a group of 209 chemicals that have very good thermal and electrical insulating properties, were widely used in industrial applications for decades beginning in 1929, when they were first commercially produced under the Aroclor trade name. Their popularity grew through the decades as they were used in numerous applications, including adhesives, cables, carbonless copy paper, caulking, floor finishes, plastics, oil-based paint, and transformers and capacitors.