Disposition of polychlorinated biphenyl congeners in occupationally exposed persons

Relative concentrations of 37 polychlorinated biphenyl (PCB) congeners and the adipose-plasma partition of 28 PCB congeners were investigated in 26 persons occupationally exposed to various PCBs (20 to 54% chlorine). Concentrations of PCBs in adipose and plasma were related to duration and intensity of exposure in the workplace. PCB concentration in adipose tissue was proportional to that in plasma, with a partition for total PCBs of approximately 190:1 indicated from regression analysis. PCB congeners with chlorines in both 4-positions of the biphenyl ring were the major components in plasma and adipose tissue. Congeners with unsubstituted 3,4-positions (e.g., 2,5-chlorine substitution) on at least one of the biphenyl rings were observed at lower concentrations and had lower adipose-plasma partition than other congeners. In contrast, those compounds with substituents at the 2,4- and/or 3,4-positions on both rings were present in much higher proportions in blood or adipose than in the PCB mixtures in use. These components also had higher adipose-plasma partition than those with unsubstituted 3,4-positions, regardless of the degree of chlorination. PCBs with 2,4-substitution patterns on both rings, including 2,4,4′-tri- and 2,4,5,4′-tetra-CBs, had somewhat higher adipose-plasma partition than congeners with 3,4-substitution on at least one of the biphenyl rings (e.g., 2,4,3′,4′-tetra-CB).