For many years, U.S. power companies and the electrical
industry used compounds known as polychlorinated
biphenyls (PCBs) to insulate electrical transformers and
other equipment. PCBs were also used as fluids in industrial
equipment in many manufacturing sectors. By the
1970s, it was recognized that PCBs were toxic to wildlife
and humans, causing damage to the reproductive,
neurological, and immune systems at high exposures.
As a result, PCBs were banned in the late 1970s. Nevethless,
these compounds still persist in the environment