A study published in 1995 and conducted by Dr. Renate D. Kimbrough of the Institute for Evaluating Health Risks, Washington D.C., and funded by the Institute and the Aluminum Company of America, concludes that doses of PCBs in humans can only be estimated, while more precise information is available for PCB-fed laboratory animals. The study further indicates that In the U.S., in PCB-exposed workers or in the adult general population, the combination of hyperpigmentation, chloracne and discolored nails have never been observed, however, these alternations in skin and nails were identified in subhuman primates following the administration of PCBs. Two major studies in the United States have examined low-level environmental exposure to PCBs. Results of this study, which concentrated on prenatal subjects, were published in the Journal of Pediatrics. Although the authors found no association between birth weight, head circumference or presence of jaundice and levels of the contaminants in any of the biological matrices, they did find elevated PCB levels were associated with hypotonicity.
Hypotonicity is a condition of having abnormally low tension or tone, especially of the muscles.
The most comprehensive studies on in utero exposure to PCBs have been conducted by Joseph L. Jacobson and Sandra W. Jacobson. These studies concentrated on infants and children who had been exposed in utero to PCBs. The PCBs were present in their mothers bodies. The Jacobsons found developmental and cognitive dysfunctions associated with fish consumption and potential prenatal exposure to PCBs. These studies have been criticized for the small size of the control group studied, the Jacobsons interpretation of analytical PCB data, and the statistical comparisons of exposed and control subjects.