A group of chemicals with the same general chemical structure and physical properties as DDT are known as polychlorinated biphenyls or PCBs. Because of their physical properties (nonflammability, chemical stability, high boiling point, and electrical insulating properties), PCBs can be used in a variety of applications. Formerly, many products contained these compounds—from electrical circuitry to the dyes and pigments used in paint to carbonless copy paper—all were manufactured with PCBs. Before production ceased in 1977, the United States produced about 1.5 billion pounds (6.8 billion kilograms) of PCBs.

Chlorofluorocarbons (CfCs) are commonly used as aerosol sprays, refrigerants, solvents, and foam-blowing agents. They are in and of themselves nontoxic and nonflammable molecules containing chlorine, fluorine, and carbon. However, they are thought to have a deleterious effect on ozone concentrations in the atmosphere (for more about the ozone and ozone depletion, see this chapter).