Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that bioaccumulate in the food chain and thus pose a health risk to human beings and other animals. The exceptional dielectric and lubricating properties of the PCBs resulted in their extensive use during the mid-1950s as lubricants in electrical generators and transformers. PCBs have a long half-life and persist in the environment causing concerns related to their toxicity. The present research on congener 118 (2,3',4,4',5-pentachlorobiphenyl) involves the quantification of hepatocyte alterations using stereology techniques. Application of a quantitative technique to estimate liver pathology confers more confidence in evaluating toxicity of a xenobiotic, and in the determination of its NOAEL (No Observable Adverse Effect Level).

Alterations in the volume fraction of cellular constituents in the hepatocytes induced by congener 118 were estimated relative to the sex of, and dose fed to a laboratory population of weanling Sprague-Dawley rats. The rats were given the PCB dose in concentrations of 2, 200, and 2,000 ppb to females and 10, 1,000 and 10,000 ppb to males; three animals were used in each dose group.