ABSTRACT
Cobalt naturally occurs in air, rocks, soils, and water, and it has diverse industrial and biomedical applications. It is an essential trace metal and cofactor for vitamin B12 (cyanocobalamin) but can be toxic after a minimal increase in concentration. Inhalation and dietary ingestion are the main external sources of cobalt exposure; however, internal exposure from cobalt hip or oral implants and the use of nanoparticles are on the rise. Cobalt is absorbed through the gastrointestinal tract and accumulated in the liver, kidney, pancreas, heart, skeleton, and skeletal muscle. The deficiency in humans with balanced diet has never been reported. It is excreted through kidney, and excretion efficiency decreases with time and elevated dose. Chronic increases of cobalt in serum may result in long-term adverse biological effects such as immune modulation, oxidative DNA damage, and maybe carcinogenesis. Serum cobalt concentrations higher than 300 µg/L are associated with neurological, cardiac, hematological, and endocrine toxicity. The higher level of cobalt in the tissue competes with calcium uptake and influences other signaling involving hypoxic response, oxidative stress, and energy metabolism. Possible abuse of cobalt supplements by athletes as an alternative to Epo doping for enhancing aerobic performance is a deep concern. Food and Drug Administration (FDA) has not established any guidance, however, the European Food Safety Authority (EFSA) has suggested a dose of 600 µg/day.
