NTP Carcinogenesis Bioassay of Propyl Gallate (CAS No. 121-79-9) in F344/N Rats and B6C3F1 Mice (Feed Study).
Propyl gallate is a white to nearly white odorless powder having a slightly bitter taste. Solutions of propyl gallate turn dark in the presence of iron or iron salts. Propyl gallate has been used since 1948 as an antioxidant to stabilize cosmetics, food packaging materials, and foods containing fats. As an additive, it may be found in edible fats, oils, mayonnaise, shortening, baked goods, candy, dried meat, fresh pork sausage, and dried milk, and it is used in hair grooming products, pressure-sensitive adhesives, lubricating oil additives, and transforming oils. A NTP Carcinogenesis bioassay of propyl gallate was conducted by feeding diets containing 6,000 or 12,000 ppm propyl gallate to groups of 50 F344/N rats and 50 B6C3F1 mice of each sex for 103 weeks. Groups of 50 untreated rats and 50 untreated mice of each sex served as controls. Survival of rats and mice was not adversely affected by propyl gallate, but mean body weights of dosed rats and mice of each sex were lower than those of the controls. At 104 weeks, mean body weights of low-and high-dose rats were 4% and 8% lower than those of the controls for males and 11% and 19% lower than those of the controls for females. Similarly, mean body weights of low-and high-dose mice were 5% and 8% lower than those of the controls for males and 11% (both dose groups) lower than those of the controls for females. Thyroid follicular-cell adenomas or carcinomas (combined) occurred in male rats with a statistically significant (P<0.05) positive trend, but the incidences in the dosed groups were not statistically significant in direct comparisons with the control groups. Moreover, the incidence of high-dose male rats with follicular-cell tumors (3/50, 6%) was not statistically different from the historical control rate (14/584, 2.4%) for the laboratory that conducted this bioassay. Rare tumors (an astrocytoma or a glioma) were found in the brains of two low-dose female rats. The incidence of all brain tumors in the Bioassay Program is only 0.86%. The absence of this tumor in the high-dose female rat group reduces the likelihood that this tumor is related to propyl gallate administration. Increased incidences of hepatic cytoplasmic vacuolization and suppurative inflammation of the prostate were observed in dosed male rats. These findings were considered to be related to administration of propyl gallate. Tumors (mostly benign) of the preputial gland, islet-cell tumors of the pancreas, and pheochromocytomas of the adrenal gland were observed with significantly (P<0.05) higher incidences in the low- dose male rats, but there was little evidence of an effect in the high-dose group. The incidences of male rats with tumors of the preputial gland were 1/50 (2%) for controls, 8/50 (16%) for the low-dose, and 0/50 (0%) for the high-dose group. Islet-cell tumors of the pancreas occurred in 2/50 (4%) control males, 9/50 (18%) low-dose males, and 4/50 (8%) for high-dose males. Pheochromocytomas of the adrenal gland were observed in 4/50 (8%) control males, 13/48 (25%) low-dose males, and 8/50 (16%) high-dose males. Negative trends (P<0.05) were observed for leukemia in male rats (16/50, 7/50, 6/50) and for fibroadenomas of the mammary gland in female rats (11/50, 2/50, 5/50). In male mice, malignant lymphoma was observed with a significantly (P</=0.014) positive trend (control, 1/50, 2%; low-dose, 3/49, 6%; high-dose, 8/50, 16%), and the incidence in the high-dose group was significantly (P</=0.028) higher than that observed in the concurrent controls. However, the high-dose incidence was not statistically different from the historical rate (60/640, 9.4%) for the laboratory that conducted this bioassay. Adenomas of the liver in female mice occurred with a statistically significant (P</=0.022) positive trend, and the incidence in the high-dose group was significantly (P</=0.039) higher than that of the controls (0/50, 0%; 2/50, 4%; 5/49, 10%). The incidences of hepatocellular adenomas or carcinomas (combined) were similar in control and dosed groups (3/50, 6%; 3/50, 6%; 5/49, 10%). Negative%; 2/50, 4%; 5/49, 10%). The incidences of hepatocellular adenomas or carcinomas (combined) were similar in control and dosed groups (3/50, 6%; 3/50, 6%; 5/49, 10%). Negative trends (P<0.05) were obtained for fibromas of the skin or subcutaneous tissue in male mice (5/50, 1/49, 0/50). Under the conditions of this bioassay, propyl gallate was not considered carcinogenic for F344/N rats, although there was evidence of an increased proportion of low-dose male rats with preputial gland tumors, islet-cell tumors of the pancreas, and pheochromocytomas of the adrenal glands; rare tumors of the brain occurred in two low-dose females. Propyl gallate was not considered to be carcinogenic for B6C3F1 mice of either sex, although the increased incidence of malignant lymphoma in male mice may have been related to the dietary administration of propyl gallate. Levels of Evidence of Carcinogenicity: Male Rats: Equivocal Female Rats: Negative Male Mice: Equivocal Female Mice: Negative Synonyms: 2,4,5 trihydroxybenzoic acid propyl ester; gallic acid propyl ester; Progallin P; Tennox PG