Polychlorinated biphenyls (PCBs) is a group of organic compounds used in the manufacture of plastics, as lubricants, and dielectric fluids in transformers, in protective coating for wood, metal and concrete, and in adhesives, wire coating and so forth. They are highly toxic to aquatic life and persist in the environment for long periods of time. They can accumulate in food chains and may produce harmful side—effects at high concentrations