ABSTRACT
Polychlorinated biphenyls (PCB’s) are complex mixtures of fat-soluble aromatic hydrocarbons, which were manufactured in the United States from 1929 until 1977. The chemical structure of PCB’s consists of biphenyl rings (C12H10) in which 1 through 10 of the hydrogen atoms are replaced with chlorine atoms, resulting in up to 209 individual chlorinated biphenyls. Commercial PCB’s are mixtures of compounds of the various isomeric groups. The trade name “Arocholor”, which was marketed in the United States, was given to the commercial chlorinated mixtures, denoting the weight-precent chlorine which generally varied between 21 and 68%. The weight-precent chlorine was designated by the last two numbers of the “grade”; for example, Arochlor 1254 contained approximately 54% chlorine by weight. The first two numbers inducate whether the mixture contains biphenyls (12), triphenyls (54), or both (25,44).
