[Subchronic toxicity study of tributoxyethyl phosphate in Wistar rats]

Tributoxyethyl phosphate (TBEP) is widely used in household materials such as plasticizer, floor polish and flame retardant in plastic resins and synthetic rubbers. This compound has been detected at ppb level in underground water. In order to elucidate the toxicity of TBEP, a 14-week oral toxicity study was conducted. Wistar rats (5-weeks old, male & female, 15 rats/group) were given diet containing 0, 0.03, 0.3 or 3.0% TBEP. Suppression of body weight gain was observed in both sexes of the 3.0% group. Serum cholinesterase activity was significantly decreased in both sexes of the 0.3 and 3.0% groups and serum gamma-glutamyl transferase activity was significantly increased in both sexes of the 3.0% group after 5 and 14 weeks exposure. Amylase in serum was also increased in 0.3 and 3.0% group males and 3.0% group females. Absolute and relative liver weights in both sexes were significantly increased in the 3.0% group after 5 and 14 weeks of exposure. Histopathological examination revealed moderate periportal hepatocyte swelling in male rats of the 3.0% group after 14 weeks exposure but this change was not found in male rats given 0.3% or less of TBEP in the diet or in any of the females. These findings indicated that the liver is a target organ for TBEP toxicity. We concluded a no-observed effect level (NOEL) of TBEP in the diet of 0.03% (male: 20 mg/kg/day, female: 22 mg/kg/day) under the conditions of this toxicity study.