In another study assessing the correlation between cancer deaths and trace metals in water supplies in the United States, no correlation was found between cancer mortality and the level of cobalt in the water. In an animal study, inhalation of cobalt over a lifetime did not increase the incidence of tumors in hamsters. Cobalt, via direct injection under the muscles or skin, has been reported to cause tumors at the injection site in animals. EPA has not classified cobalt for carcinogenicity. Physical Properties Cobalt usually occurs in the environment in association with other metals such as copper, nickel, manganese, and arsenic.
Pure cobalt is a steel-gray, shiny, hard metal that is insoluble in water.
U.S. Department of Health and Human Services. National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993. U.S. Department of Health and Human Services. National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993. U.S. Environmental Protection Agency.