WHAT ARE PCBs?

Background

Polychlorinated biphenyls or PCBs are a group of chemicals that are characterized by two phenyl groups, with varying number of chlorine atoms as shown below.

A specific PCB molecule is called a congener and is named by the number and location of the chlorine atoms. PCBs were sold as commercial mixtures of many PCB molecules or congeners and were mostly sold as Aroclors, but also Kanochlor and other trade names. The Aroclor number refers to the percent chlorine by weight (e.g., Aroclor 1248 was approximately 48% chlorine by weight). In general, the higher the chlorination of the PCB molecule and mixtures, the greater the tendency to persist in the environment for long periods as well as accumulate up the food chain. This chemical stability was an essential property for its commercial uses; it has low flammability, it only boils at higher temperatures and can serve well to insulate electrical processes.
PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics and rubber products; in pigments, dyes and carbonless copy paper and many other applications. More than 1.5 billion pounds of PCBs were manufactured in the United States prior to cessation of production in 1977. [taken from: U.S. EPA PCB Home Page].