Toxicology and carcinogenesis studies of dietary titanium dioxide‐coated mica in male and female Fischer 344 rats

Abstract

Male and female Fischer 344 rats were fed diets containing 0, 1.0, 2.0, or 5.0% titanium dioxide (TiO2) coated mica for up to 130 wk. The dosage regimen produced no consistent or biologically important changes in survival, body weight gains, or hématologic or clinical chemistry parameters. Ophthalmoscopic examinations during wk 104 revealed a dose‐related increase in the incidence of cataracts in male but not female rats. However, the incidences of microscopic cataracts were similar in all groups of male and female rats. The high dose of TiO2‐coated mica was associated with a slightly increased incidence of adrenal medullary hyperplasia in males, but there was no evidence of progression of this change to either benign or malignant pheochromocytoma and there was no evidence of an adrenal medullary proliferative response in females. The incidence of mononuclear cell leukemia was elevated in high‐dose males that survived to the termination of the study, but there was no evidence that TiO2‐coated mica either induced or hastened the onset of the disease. Under the conditions of this experiment there was no evidence that TiO2‐coated mica produced either carcinogenic or toxicologic effects at dietary concentrations as high as 5.0%.