Dietary concentrations of 0, 20, 100, and 500 ppm of technical grade pentachlorophenol were fed to male and female Sherman strain rats for 8 months. The same experiment using purified pentachlorophenol was carried out. The food consumption was measured in all rats during the second week of exposure and for one week every 6 weeks thereafter. An autopsy was performed on all rats at the end of the experiment. The brain, lungs, spleen, liver, kidneys, heart, and testes were weighed and examined grossly and microscopically in all rats fed purified pentachlorophenol, all female rats fed technical pentachlorophenol, and in the male rats fed the highest dose of technical pentachlorophenol and the controls. Only the kidneys and livers were examined microscopically in the male rats fed 20 and 100 ppm of technical pentachlorophenol. Although the food intake was comparable, male and female rats fed 500 ppm of technical and male rats fed 500 ppm of purified pentachlorophenol gained less weight. The livers of the male and female rats fed 500 ppm technical pentachlorophenol weighed significantly more than those of the controls. The kidneys of all male rats fed purified pentachlorophenol weighed significantly more than those of the controls; however, there was no dose-related increase. No morphological changes were seen in the kidneys. At the 500-ppm dietary concentrations, technical pentachlorophenol produced a severe effect in the liver of female rats characterized by vacuolation of the hepatocytes, an increase in fibroblasts and other mononuclear cells within sinusoids, bile duct proliferation, periportal fibrosis, degenerated liver cells, increased mitotic figures, and an accumulation of brown pigment in macrophages and in Kupffer cells. In male rats at the 100- or 500-ppm dietary concentrations of technical pentachlorophenol, the predominant lesion consisted of enlarged pleomorphic hepatocytes which had foamy cytoplasm or cytoplasm with large vacuoles. The walls of the
hepatic central veins of the livers in animals of both sexes were thickened. At the 100-ppm dietary concentrations similar but less pronounced effects were observed in the livers. Only mild alterations were noted at the 20-ppm dietary concentration. Purified pentachlorophenol caused slightly enlarged liver cells with occasional eosinophilic cytoplasmic inclusions at 500 ppm but no alterations were observed in the livers of rats fed the 100- and 20-ppm dietary concentrations. The results suggest that most of the toxicity associated with feeding technical grade pentachlorophenol to rats at these dietary concentrations stems from toxic contaminants rather than from pentachlorophenol.