Toxicity and carcinogenicity of t-butyl alcohol in rats and mice following chronic exposure in drinking water.

t-Butyl alcohol (TBA) was administered in drinking water to F344/N rats and B6C3F1 mice for two years using 60 animals/dose/sex/species. Male rats received doses of 0, 1.25, 2.5, or 5 mg/ml and females received 0, 2.5, 5, or 10 mg/ml, resulting in average daily doses of approximately 85, 195, or 420 mg TBA/kg body weight for males and 175, 330, or 650 mg/kg for females. Ten rats per group were evaluated after 15 months. Male and female mice received doses of 0, 5, 10, or 20 mg/ml, resulting in average daily doses of approximately 535, 1,035, or 2,065 mg TBA/kg body weight for males and 510, 1,015, or 2,105 mg/kg for females. Survival was significantly reduced in male rats receiving 5 mg/ml, female rats receiving 10 mg/ml, and male mice receiving 20 mg/ml. Long-term exposure to TBA produced increased incidences of renal tubule adenoma and carcinoma in male rats; transitional epithelial hyperplasia of the kidney in male and female rats; follicular cell adenoma of the thyroid in female mice; and follicular cell hyperplasia of the thyroid and inflammation and hyperplasia of the urinary bladder in male and female mice. In addition, a slight increase in follicular cell adenoma or carcinoma of the thyroid (combined) in male mice may have been related to the administration of TBA.