Polychlorinated terphenyls (PCTs) use, levels and biological effects.

Polychlorinated terphenyls (PCTs) have almost identical characteristics to high chlorinated PCBs: extremely stable, bioaccumulable and biomagnification through food webs might take place. PCT is especially used in investment casting waxes and as a substitute for PCB. In spite of the limited use until now, PCT has been detected in a great variety of environmental samples such as soil, water, shellfish, fish, seals, birds and terrestrial animals. Furthermore, it has been found in paper products and foodstuffs. PCT residues in human tissues--blood, liver, fat and milk--have been detected in some countries. Animal experiments have shown that long-term toxic effects of PCT are of most importance. PCT has a marked inductive effect on the microsomal enzymes in the liver in vertebrates and may cause liver-damage--including tumours. Disturbance of the hormonal--and immunological--systems have also been reported. The most important ecological hazard of PCT--as well as PCB--is the possible disturbance of the reproduction system of the organisms. Many countries do not regulate the use of PCT. In some countries the use of PCT is regulated to closed systems, but the expansion of usage is under consideration in the EEC.