Because of their physico-chemical properties PCB s have been used since 1929 as insulating fluids in transformers and capacitors, as hydraulic oils, lubricants, softeners,heat exchange fluids, additives in plastics, casting oils etc.,and are still in use today. Most of the PCB s were produced during the period 1950 to 1983. Total world production has been estimated to be more than 1 million metric tonnes. Subsequent research has shown PCB s to be ubiquitously present, both in human beings and the environment. The PCB s produced in Germany were manufactured by the only German producer , the Bayer corporation.
Open systems release the PCB s successively to the environment.
Of the uses specified there, only the use in transformers and capacitors and as hydraulic oil in underground mining plays a role in Germany. In order to calculate emissions from open- and closed systems by use of emission factors it is necessary to estimate the amount of PCB still in use. The quantification of PCB s in open systems still in use is very difficult. Although the use of PCB s in varnishes, inks,special papers, plastics, sealants etc. By definition, closed systems should not emit PCB s at all.