Inhalation toxicity and carcinogenicity studies of cobalt sulfate

Area of Science:

• Toxicology
• Occupational Health
• Carcinogenesis

Background:

• Cobalt sulfate is a widely used industrial and agricultural chemical.
• Previous studies suggested potential carcinogenicity of cobalt compounds, but lacked occupational exposure relevance.
• Adequate rodent carcinogenicity studies for soluble cobalt salts via inhalation were missing.

Purpose of the Study:

• To assess the carcinogenicity of cobalt sulfate hexahydrate in rats and mice via inhalation.
• To investigate the non-neoplastic effects of chronic cobalt sulfate inhalation.
• To establish dose-response relationships for cobalt sulfate-induced toxicity and carcinogenicity.

Main Methods:

• Groups of rats and mice (50 males, 50 females) were exposed to 0, 0.3, 1.0, or 3.0 mg/m3 cobalt sulfate hexahydrate aerosols for 6 hours/day, 5 days/week, over 104 weeks.
• Survival, body weight, and detailed histopathological examinations of major organs were conducted.
• Statistical analyses were performed to determine significant increases in tumor incidence and non-neoplastic lesions.

Main Results:

• Cobalt sulfate inhalation caused significant increases in alveolar/bronchiolar neoplasms in both male and female rats and mice.
• A spectrum of inflammatory, fibrotic, and metaplastic lesions were observed in the respiratory tracts of exposed rats and mice.
• Increased incidences of adrenal pheochromocytomas were noted in female rats and possibly male rats.

Conclusions:

• Inhalation exposure to cobalt sulfate hexahydrate is carcinogenic in rats and mice, primarily causing lung tumors.
• Cobalt sulfate induces significant non-neoplastic lesions in the respiratory system.
• Findings suggest a potential occupational cancer risk for humans exposed to cobalt sulfate via inhalation.