Pcbs: Not Just a Local Problem

Polychlorinated Biphenyls

a. Basic Chemical Structure and Makeup:

Polychlorinated Biphenyls (PCBs) are man made chemicals whose birth came in the early Twentieth Century. They are not found anywhere in nature, and are classified by chemists as chlorinated oils with a low degree of reactivity.

Regarding the chemical structural of PCBs, two distinct groups of this compound can be established: Basic PCB Structure and Toxic PCB Structure. The basic structure is comprised of a biphenyl (two benzene rings with a carbon to carbon bond) with a varying number of bonded chlorine molecules along the outside of the biphenyl structure. The toxicity of this compound, however, is dependent upon how many chlorine molecules are present on the biphenyl structure. Thus the more chlorine molecules contained within a PCB, the more toxic the actual compound is. (See figure I.I)

Toxicity is not the only chemical aspect whose scale and extent is dependent upon the number of chlorine molecules