title: Bioassay of dimethyl terephthalate for possible carcinogenicity.
abstract: A bioassay of dimethyl terephthalate for possible carcinogenicity was conducted by administering the test chemical in feed to F344 rats and B6C3F1 mice. Groups of 50 rats of each sex and 50 mice of each sex were administered dimethyl terephthalate at one of two doses, either 2,500 or 5,000 ppm, for 103 weeks, then observed for 2 additional weeks. Matched controls consisted of 50 untreated rats of each sex and 50 untreated mice of each sex. All surviving rats were killed at 105 or 106 weeks and all surviving mice at 104 or 105 weeks. Administration of dimethyl terephthalate had no appreciable effect on the mean body weights of the rats and mice of either sex. No clinical signs related to administration of the test chemical were noted in the rats. Survivals of the rats and mice at the end of the bioassay were not affected by the test chemical. Both species may have been able to tolerate higher doses. In rats and mice of each sex, no tumors occurred at incidences that clearly were related to administration of the test chemical. Although it is recognized that both rats and mice may not have received a dose of the test chemical sufficiently high to provide maximum test sensitivity, it is concluded that under the conditions of this bioassay, dimethyl terephthalate was not carcinogenic for F344 rats or B6C3F1 mice.