Inhalation Toxicity Studies of Cobalt Sulfate in F344/N Rats and B6C3F1 Mice

Inhalation Toxicity Studies of Cobalt Sulfate in F344/N Ratsand B6C3F1 Mice. BUCHER, J. R., ELWELL, M. R., THOMPSON, M.B., CHOU, B. J., RENNE, R., AND RAGAN, H. A. (1990). Fundam.Appl. Toxicol. 15, 357–372. Groups of 10 F344/N rats andB6C3F1 mice of each sex were exposed to cobalt sulfate heptahydrateaerosols of 0, 0.3, 1.0, 3.0, 10, or 30 mg/m3, 6 hr per day,5 days per week, for 13 weeks. All rats and female mice andall but 2/10 male mice exposed at the top concentration survivedto the end of the studies. Polycythemia was observed in exposedrats but not in mice. Sperm motility was decreased in mice exposedat 3 mg/m3 (the lowest concentration evaluated) and at higherconcentrations, and increased numbers of abnormal sperm anddecreased testis and epididymal weights occurred in mice exposedto 30 mg/m3. Cobalt content in the urine of rats increased withincreasing atmospheric cobalt exposure. Primary histopathologiceffects were limited to the respiratory tract. Lesions in ratsand mice included degeneration of the olfactory epithelium,squamous metaplasia of the respiratory epithelium, and inflammationin the nose; inflammation, necrosis, squamous metaplasia, ulcers(rats), and inflammatory polyps (rats) of the larynx; metaplasiaof the trachea (mice); and fibro-sis, histiocytic infiltrates,bronchiolar epithelial regeneration, and epithelial hyperplasiain the alveoli of the lung. The most sensitive tissue was thelarynx, with squamous metaplasia observed in rats and mice atthe lowest exposure concentration of 0.3 mg/m3. Thus, a no-observed-adverse-effectlevel was not reached in these studies