In contrast to dioxins, polychlorinated biphenyls (PCBs) were manufactured in large quantities and found a wide range of applications due to their high thermal, chemical and electrical stability. They were first produced commercially around 1930 and approximately 66,500 tonnes were manufactured in the UK between 1951 and 1976. Of this, around 27,000 tonnes were exported to other countries where it would have been used in a range of products. There are no figures available on quantities of PCBs imported into the UK.
Monsanto (Solutia) was the only known producer of PCBs until 1976, based at Newport.
Commercial PCBs were manufactured by the direct chlorination of biphenyl leading to the production of oils containing mixtures of PCB congeners with between 21 per cent and 60 per cent chlorine. Commercial PCB mixtures were sold under a variety of trade names, the most common in the UK being the “Arochlor” range. While most literature focuses on only those PCB congeners with “dioxin-like” properties, sources will release a range of congeners, many of which will not possess such properties.