Footnote

a PCBs (polychlorinated biphenyls), in widespread use since the 1930’s, are a family of over 200 oily compounds used in lubricants, plastics, electrical insulation, pesticides, dishwashing liquids, and other products. Though PCB production is now banned in many countries, between one and two million tons have been manufactured. Toxic effects have resulted from discarded PCBs that have found their way into the environment.