Literature Review

Abstract

Cobalt is a relatively rare element of the Earth’s crust, essential to mammals in the form of cobalamin (vitamin B12). In humans, dietary intake of cobalt varies between 5 and 50 μg/day and most of it is inorganic with vitamin B12 representing only a small fraction. The oral bioavailability of inorganic cobalt compounds is a function of their water solubility and varies from 5 to 45%. In occupational settings, workers are exposed to mainly inorganic cobalt compounds by inhalation of dust. The absorption rate of inhaled cobalt also varies with the species under consideration. Cobalt does not accumulate in the organism and is rapidly excreted, mainly in urine. The concentration of cobalt in urine or in blood can be used as a biomarker of recent exposure to soluble cobalt species. Cobalt(II) ions are genotoxic and several forms of cobalt are carcinogenic in experimental animals. Upon inhalation exposure, the respiratory system is the main target organ of cobalt in humans (asthma, fibrosing alveolitis, lung cancer), with a higher risk of fibrosing alveolitis (hard metal disease) and lung cancer in the hard metal industry, where workers are exposed to cobalt metal mixed with tungsten carbide particles. Other target organs include the hematopoietic system, the myocardium, the thyroid gland, and the nervous system. Endogenous exposure to cobalt, sometimes associated with local and/or systemic toxicity, can occur in patients with cobalt alloy implants, especially metal-on-metal hip prostheses. The reproductive toxicity of cobalt compounds is not well documented.