Carcinogenicity test of polyoxyethylene(10) nonylphenyl ether (NP-10) in female B6C3F1 mice

A carcinogenicity study of polyoxyethylene(10)nonylphenyl ether (NP-10) to B6C3F1 mouse was performed using 50 females per group of 4 study groups, or 200 mice in total. Diets containing NP-10 at 0, 500, 1500 and 4500 ppm were prepared and orally administered to the animals repeatedly for 104 weeks, and observation of general conditions, body weight analysis, food consumption analysis, hematologic examination, organ weight analysis and pathological examination were performed. The results are summarized as follows. The mean intake of the test substance in the 500, 1500 and 4500 ppm groups for 104 weeks was 81.5, 254 and 873 mg/kg/day, respectively. There were no differences observed in mortality among the groups and the mortality did not exceed the background data in any groups. There were no signs attributable to the administration of the test substance, and various signs which increased in occurrence with aging were observed in all groups at a similar frequency. Body weight gain was suppressed only in the 4500 ppm group throughout the entire administration period. Food consumption was increased in all treated groups around the early stage of administration and, thereafter, in the 1500 and 4500 ppm groups until the mid-stage of administration. Decreased food efficiency was observed in the 4500 ppm group alone. As a result of the hematologic examination, no changes attributable to the administration of the test substance were observed in any groups. As a result of the organ weight analysis, lower absolute weights of the liver and kidney and higher relative weights of the brain, liver and kidney, which were considered to be changes accompanying the suppressed body weight gain, were observed in the 4500 ppm group. The pathological examination revealed no marked changes in the gross findings in the treated groups. As a result of the histological examination, there were no neoplastic or non-neoplastic lesions in the treated groups which were unequivocally observed to have increased in occurrence. As the above findings show, NP-10 did not cause any increase in the incidence of neoplastic lesions in the mouse by oral administration for 2 years at 873 mg/kg/day (4500 ppm) and was determined to have no carcinogenicity.