* DDT, or dichlorodiphenyltrichloroethane, is toxic to human beings and animals when swallowed or absorbed through the skin. It was widely used in the mid-twentieth century and has been banned in the United States for most uses since 1972. PCBs, or polychlorinated biphenyls, are a class of organic compounds and an environmental pollutant associated with birth defects and cancer. The 1975 Toxic Substances Control Act required that the production of PCBs be phased out within three years.