Cardiac effects, congestion of the liver, kidneys, and conjunctiva, and immunological effects have also been noted in humans. Chronic exposure to high levels of cobalt via ingestion has resulted in cardiovascular effects in humans, with effects including cardiogenic shock, sinus tachycardia, left ventricular failure, and an enlarged heart. Cobalt is an essential element in humans, as a constituent of vitamin B 12 . No information is available on the reproductive or developmental effects of cobalt in humans via inhalation exposure. In an oral study, no developmental effects on human fetuses were observed following treatment of pregnant women with cobalt chloride.
Limited data are available on the carcinogenic effects of cobalt.
Human studies are inconclusive regarding inhalation exposure to cobalt and cancer, and the one available oral study did not report a correlation between cobalt in the drinking water and cancer deaths. One animal study did not report an increase in tumor incidence in hamsters from inhalation exposure to cobalt. EPA has not classified cobalt for carcinogenicity. Cobalt is an essential element in humans and animals as a constituent of vitamin B 12 . Cobalt has also been used as a treatment for anemia, because it stimulates red blood cell production.