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Certain former operations in capacitor manufacturing resulted in extensive direct contact of the workers with electrical grade polychlorinated biphenyls (PCBs). A study group of 194 such individuals, all exposed to Aroclor 1016 and many previously exposed to Aroclors 1242 and/or 1254, was examined before (1976) and after (1979) discontinuance of PCB use in the operations (1977). At the two examinations, the approximate geometric mean serum levels (in ppb) and 5 to 95% ranges were for lower PCBs (LPCB), 363 (57-2270) and 68 (12-392); and for higher PCBs (HPCB), 30 (6-142) and 19 (4-108), respectively.The statistical associations among 42 measured clinical chemical and hematological parameters, five different measures of PCB exposure, and seven confounding variables observed in the two examinations were determined by three regression procedures. Similar regressions were performed with DDE, which was present at background levels. The principal statistical findings were a depression in serum bilirubin and elevations in serum GGTP and lymphocyte levels at the time of the first examination, and only an elevation in monocytes at the second. Appraisal of the results suggested an induction of microsomal enzymes which appeared to be subsiding after the cessation of direct exposure to PCBs. The statistical association between serum levels of PCBs and lipids reported by others was confirmed, but shown to be explained by the partitioning behavior of PCB in the body, rather than to changes in liver function. No evidence for health impairment related to PCBs was found, despite the high serum levels of PCBs in the study population.

The 95% prediction interval for single measurements of serum "Aroclor" reported by a reputable commercial analyst was found to be approximately +/- 42%. The geometric mean serum PCB levels in a population of capacitor workers who had formerly had direct exposure to the commercial PCBs--Aroclors 1016, 1242, and 1254-were found to be alternatively reportable as 1905 ppb minimum initial PCBs (as calculated from most persistent peaks present); 1093 ppb non-overlapping analytical "Aroclor" levels (as calculated by the conventional sum-of-the-peak-heights method); 303 ppb total PCBs actually present; or 19 ppb "human PCB" (as calculated by the NHMP procedure). The broad spread in reportable values was relatable to the PCB isomer distribution and clearance patterns in the occupationally exposed population.

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