Polychlorinated biphenyls, or PCBs, are a family of different manmade chemicals which exhibit long environmental and biologic half-lives. They are no longer produced in the United States, but previously were used in electrical equipment due to their insulating properties and relative non-flammability. Over the years, our staff has studied dozens of sites where PCBs were the primary “chemicals of principal concern” and we have published a number of articles on how to assess their risks to humans. Several of our staff has provided expert testimony on this family of chemicals in court proceedings.