Bioassay of 2,3,5,6-tetrachloro-4-nitroanisole for possible carcinogenicity (CAS No. 2438-88-2).

A bioassay for possible carcinogenicity of 2,4,5,6-tetrachloro-4-nitroanisole was conducted using Fischer 344 rats and B6C3F1 mice. 2,3,5,6-Tetrachloro-4-nitroanisole was administered in the feed, at either of two concentrations, to groups of male and female animals of each species. The high and low dietary concentrations used in the chronic bioassay were 0.012 and 0.006 percent, respectively, for both species. After a 104-week period of chemical administration, observation of rats continued for up to 3 weeks and observation of mice continued for up to 1 week. For rats 50 animals of each sex were placed on test as controls, while for mice 55 animals of each sex were placed on test as controls. There were no significant positive associations between the dietary concentration of 2,3,5,6-tetrachloro-4-nitroanisole administered and mortality in rats or mice of either sex. Adequate numbers of animals in all groups survived sufficiently long to be at risk from late-developing tumors. No neoplasms, except for interstitial-cell testicular tumors in males, occurred at statistically significant incidences in dosed rats. Because of the high and variable spontaneous incidence of these lesions in Fischer 344 rats, these tumors were not considered to be associated with the administration of the test compound. Among dosed male mice the combined incidence of leukemia and malignant lymphoma was statistically significant. However, since these lesions were not spontaneously and with high variation in B6C3F1 mice, the lesions were not considered to be associated with the administration of the test compound. No neoplasms were of a statistically significant incidence in dosed female mice. Under the conditions of this bioassay, dietary administration of 2,3,5,6-tetrachloro-4-nitroanisole was not carcinogenic to male or female Fischer 344 rats or B6C3F1 mice of either sex.