PCBs form a group of compounds which were developed in the 1930s and were mainly used in the electricity supply industry and mining. Due to their accumulation in the food chain, production of PCBs was halted world-wide at the beginning of the 1980s and in 1996 an EC Directive was agreed requiring a phase-out of continuing uses (mainly in ageing electrical equipment). PCBs are, however, still found in trace concentrations in the sea and in the fatty tissue of marine animals.