title: Bioassay of hexachlorophene for possible carcinogenicity.
abstract: A bioassay of hexachlorophene for possible carcinogenicity was conducted by administering the test chemical in feed to Fischer 344 rats. Groups of 24 rats of each sex were administered hexachlorophene at one of three doses, either 17, 50, or 150 ppm, for 105-106 weeks. Higher doses of 200-600 ppm, used in 8-week subchronic studies, induced neuronal necrosis of the brain and clinical signs of toxicity. Matched-control groups consisted of 24 untreated rats of each sex. All surviving animals were killed at 105-106 weeks. Mean body weights of the rats were unaffected by the hexachlorophene, and no clinical signs of toxicity were recorded. Survival also was unaffected, and adequate numbers of animals survived, permitting meaningful evaluation of the incidences of late-appearing tumors. No tumors were present in a statistically significant incidence at any site in the treated rats. It is concluded that under the conditions of this bioassay, hexachlorophene did not induce malignant or benign tumors in Fischer 344 rats.