Polychlorinated Biphenyls (PCBs)

Black and white chemical structure of PCB 153

Structure of PCB 153, a polychlorinated biphenyl

CAS Number: various

PCBs were once widely used to insulate electrical equipment and as plasticizers.  PCBs were banned in the late 1970s but are still in some old equipment and products.  They have spread through the environment and take a long time to break down.

 Also see Hydroxy-PCBs.