NTP Toxicology and Carcinogenesis Studies of Triethanolamine (CAS No. 102-71-6) in F344 Rats and B6C3F1 Mice (Dermal Studies).
Triethanolamine is widely used as an ingredient in emulsifiers, thickeners, wetting agents, detergents, and alkalinizing agents in cosmetic products; as a chemical intermediate for anionic and nonionic surfactants and surface active agents in household cleaning agents, textiles, herbicides, pharmaceutical ointments, and other products; as a vulcanization accelerator in the manufacture of rubber; and in many other industrial applications. The National Cancer Institute nominated triethanolamine for study because of its widespread use in cosmetics and other consumer products, its high potential for worker exposure due to its many industrial uses, and its potential for conversion to the carcinogen N -nitrosodiethanolamine. Dermal application was chosen as the route of exposure to mimic the principal means of human exposure to triethanolamine and because considerable systemic exposure is achieved with this route. Male and female F344/N rats and B6C3F1 mice received triethanol amine (purity 98% or greater) by dermal application for 13 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melano gaster, and mouse peripheral blood erythrocytes. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were topically administered 0, 125, 250, 500, or 1,000 mg triethanolamine per kilogram body weight in acetone or 2,000 mg/kg neat triethanolamine, 5 days per week, for 13 weeks. All rats survived to the end of the study. Final mean body weights and weight gains of males and females administered 2,000 mg/kg and the mean body weight gain of females administered 1,000 mg/kg were significantly less than those of the vehicle controls. Clinical observations included irritation, scaliness, and crustiness of the skin at the site of application for males and females. Males also had discoloration, and two males administered 2,000 mg/kg had ulceration at the site of application. Changes in clinical pathology parameters were minor and consistent with inflammation at the site of application. Kidney weights were generally greater in males and females administered 500, 1,000, or 2,000 mg/kg than in the vehicle controls. Microscopic lesions attributed to triethanolamine administration included acanthosis and inflammation at the site of application, nephropathy in females, and hypertrophy of the pituitary gland pars intermedia in males and females. These lesions generally occurred with dose-related increases in incidence and severity in males and females. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were topically administered 0, 250, 500, 1,000, or 2,000 mg triethanolamine per kilogram body weight in acetone or 4,000 mg/kg neat triethanolamine, 5 days per week, for 13 weeks. All mice survived to the end of the study. The final mean body weight and weight gain of males in the 250 mg/kg group were less than those of the vehicle controls. Clinical findings were observed only in mice in the 4,000 mg/kg groups and included scaliness, irritation, and discoloration at the site of triethanolamine application for males and females and skin erosion at this site in one male. The absolute kidney and liver weights of males and females administered 4,000 mg/kg were greater than those of the vehicle controls; relative kidney weights of males administered 1,000 mg/kg or greater and females in all dosed groups were also greater than those of the vehicle controls. Microscopic examination of the skin of dosed mice indicated acanthosis and inflammation at the site of application. Acanthosis occurred in all dosed groups and in one vehicle control female; the severity increased with increasing dose in males and females. Inflammation was observed in males and females in the 4,000 mg/kg groups and in one female in the 2,000 mg/kg group. 2-YEAR STUDY IN RATS: Based on the presence of acanthosis and inflammation at the site of application at the higher doses in the 13-week study, triethanolamine doses selected for the 2-year study in rats were 32, 63, and 125 mg/kg for malesr males and 63, 125, and 250 mg/kg for females. Groups of 60 male and 60 female rats were topically administered triethanolamine in acetone 5 days per week for 103 weeks. Ten male and ten female rats from each group were evaluated at 15 months for organ weights and histopathology. Survival, Body Weights, Clinical Findings, and Organ Weights: The survival rate of females in the 250 mg/kg group was slightly less than that of the vehicle controls. The mean body weight of females administered 250 mg/kg ranged from 9&percnt; to 12&percnt; less than that of the vehicle controls between weeks 73 and 93. Male and female rats receiving triethanolamine had irritated skin at the site of application; in dosed females, the site of application also had a crusty appearance. The number of animals in which these findings were observed increased with increasing dose. At the 15-month interim evaluation, the absolute left and right kidney weights and relative right kidney weight of females administered 250 mg/kg were significantly greater than those of the vehicle controls. Pathology Findings: The incidence of acanthosis at the site of application in males administered 125 mg/kg and the incidences of acanthosis, inflammation, and ulceration in dosed females were greater than in the vehicle controls at the 15-month interim evaluation and at the end of the 2-year study. Males in the 125 mg/kg group also had greater incidences of inflammation and ulceration than the vehicle controls, and females receiving 125 or 250 mg/kg had greater incidences of epidermal erosion than the vehicle controls at 2 years. There were no skin neoplasms at or away from the site of application that were considered related to treatment with triethanolamine. At the end of the study, renal tubule adenomas were observed in seven dosed males and in one vehicle control female and one female in the 63 mg/kg group. One male in the 125 mg/kg group and one female in the 250 mg/kg group had renal tubule hyperplasia. Extended (step-section) evaluation of the kidneys of all male rats revealed additional renal tubule adenomas in one vehicle control male, one male in the 32 mg/kg group, two males in the 63 mg/kg group, and three males in the 125 mg/kg group (including one male from the 15-month interim evaluation). An oncocytoma was also identified in one male in the 32 mg/kg group. Hyperplasia was identified in eight additional vehicle control males and in 19 additional dosed males. The total incidences (combined standard and extended evaluations) of renal tubule adenoma in dosed male rats were slightly greater than the vehicle control incidence (vehicle control, 1/50; 32 mg/kg, 2/50; 63 mg/kg, 6/49; 125 mg/kg, 4/50). The total incidence of hyperplasia in dosed and vehicle control males was similar (9/50, 8/50, 7/49, 6/50). The severity of hyperplasia in males in the 32 and 125 mg/kg groups was greater than that in the vehicle controls. 2-YEAR STUDY IN MICE: Based on dose-related inflammation at the site of application in the 13-week study, triethanolamine doses selected for the 2-year study in mice were 200, 630, and 2,000 mg/kg for males and 100, 300, and 1,000 mg/kg for females. Groups of 60 male and 60 female mice were topically administered triethanolamine in acetone 5 days per week for 103 weeks. Ten male and ten female mice from each group were evaluated at 15 months for organ weights and histopathology. Survival, Body Weights, Clinical Findings, and Organ Weights: Survival rates of all dosed groups of males and females were similar to those of the vehicle controls. The mean body weight of males administered 2,000 mg/kg ranged from 8&percnt; to 10&percnt; less than that of the vehicle controls from week 69 through the end of the study. Clinical findings included irritation and discoloration of the skin at the site of application for most males in the 2,000 mg/kg group and a few females in the 1,000 mg/kg group; males administered 200 or 630 mg/kg also had skin irritation. At the 15-month interim evaluation, the right kidney weights of male mice that received 630 or 2,000 mg/kg and the left kidney weights of males that received 2,000 mg/kg were significantly greater than those of the vehicle controls. Pathology Findings: Acanthosis and inflammation of the skin were observed at the site of application in male and female mice at the 15-month interim evaluation and at the end of the 2-year study. In males in the 2,000 mg/kg group, the incidences of both lesions were significantly greater than those in the vehicle controls at both time points; however, the severities of acanthosis and inflammation did not increase with dose. At the end of the study, the incidence of inflammation in females in the 1,000 mg/kg group was significantly greater than that in the vehicle controls. One vehicle control male and two males in each of the 630 and 2,000 mg/kg groups had ulcers at the site of application. At the 15-month interim evaluation, hepatocellular carcinomas were observed in dosed and vehicle control males and hepatocellular adenomas in dosed and vehicle control males and females; however, the incidences were not dose related. Nonneoplastic lesions observed at 15 months included foci of cellular alteration in a few dosed males and females; eosinophilic foci were also observed in two vehicle control females. At the end of the 2-year study, females in the 1,000 mg/kg group had significantly greater incidences of hepatocellular adenoma and multiple adenomas and a greater combined incidence of hepatocellular adenoma and carcinoma than the vehicle controls (adenoma: vehicle control, 22/50; 100 mg/kg, 22/50; 300 mg/kg, 24/50; 1,000 mg/kg, 40/50; multiple adenomas: 11/50, 9/50, 13/50, 29/50; combined adenoma and carcinoma: 23/50, 26/50, 28/50, 41/50). Females in the 300 mg/kg group had significantly greater incidences of hepatocellular carcinoma (1/50, 4/50, 7/50, 5/50) and eosinophilic foci (9/50, 10/50, 18/50, 16/50) than the vehicle controls. Incidences of hepatocellular adenoma and multiple adenomas in males in the 2,000 mg/kg group were significantly greater than those in the vehicle controls (adenoma: vehicle control, 27/50; 200 mg/kg, 27/50; 630 mg/kg, 29/50; 2,000 mg/kg, 37/50; multiple adenomas: 17/50, 18/50, 17/50, 29/50). Three males in the 2,000 mg/kg group had hepatoblastomas, and males in this group also had significantly greater incidences of hepatocellular neoplasms (combined) (adenoma, carcinoma, and hepatoblastoma: 31/50, 34/50, 33/50, 42/50) and eosinophilic foci (10/50, 17/50, 11/50, 23/50) than the vehicle controls. Male mice had a pattern of nonneoplastic liver lesions along with silver-staining helical organisms within the liver which suggested an infection with Helicobacter hepaticus. With polymerase chain reaction-based assays and culture, the presence of an organism compatible with H. hepaticus was confirmed. An increased incidence of hepatocellular neoplasms in male mice has been shown to be associated with H. hepaticus infection when hepatitis is also present. Therefore, interpretation of the increased incidence of hepatocellular neoplasms in mice was confounded. GENETIC TOXICOLOGY: Triethanolamine was not mutagenic in any of the in vitro or in vivo short-term tests performed by the NTP. It did not induce mutations in Salmonella typhimurium, and no induction of sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells exposed to triethanolamine was noted. These in vitro tests were conducted with and without S9 metabolic activation. Triethanolamine did not induce sex-linked recessive lethal mutations in germ cells of adult male Drosophila melanogaster exposed by feeding or injection. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood samples of male and female mice that received dermal applications of triethanolamine for 13 weeks. CONCLUSIONS: Under the conditions of these dermal studies, there was equivocal evidence of carcinogenic activity of triethanolamine in male F344/N rats based on a marginal increase in the incidence of renal tubule cell adenoma. There was no evidence of carcinogenic activity in female F344/N rats receiving 63, 125, or 250 mg triethanolamine per kilogram body weight. The study in male and female B6C3F1 mice was considered inadequate, because the presence of a Helicobacter hepaticus infection complicated inter pretation of the relationship between triethanolamine administration and liver neoplasms in these animals. Dosed rats and mice had varying degrees of acanthosis and inflammation, dosed rats had ulceration, and dosed female rats had epidermal erosion at the site of skin application. Synonyms: Nitrilo-2,2',2"-triethanol; 2,2',2"-nitrilotriethanol; 2,2',2"-nitrilotrisethanol; TEA; triaethanolamin-NG; triethanolamin; triethylolamine; tri(hydroxyethyl)amine; 2,2',2"-trihydroxytriethylamine; trihydroxytriethylamine; tris(hydroxyethyl)amine; tris(2-hydroxyethyl)amine; triethylolamine; trolamine Trade Names: Daltogen; Sterolamide; Thiofaco T-35