Cobalt is extensively mined, has numerous industrial uses, and is an essential trace element in vitamin B12. 60Cobalt is remarkably important in radiotherapy, but an epidemic of cardiomyopathy ensued when cobalt was added to beer to improve the esthetics of the "foam." Toxicologic concerns today have diminished because of preventive respiratory measures in the mining industry. The ingestion of cobalt salts is quite uncommon.
The name cobalt (Co) originates from kobold German for "goblin," and was given to the cobalt-containing ore cobaltite (CoAsS) because it made exposed miners ill. However, the miners' illness was more likely a result from the arsenic exposure rather than exposure to cobalt. Brandt discovered cobalt in 1753 during an attempt to prove that an element other than bismuth gave glass a blue hue.
With an atomic number of 27 and a molecular weight of 58.93 daltons, Co is a light metal that has a melting point of 1768.2°K and a boiling point of 3373°K. These attributes make elemental cobalt a very useful industrial metal. The main industrial use of cobalt use is the formation of hard, high-speed, high-temperature cutting tools. When aluminum and nickel are blended with cobalt, an alloy (Alnico) with magnetic properties is formed. Other uses for cobalt include electroplating because of its resistance to oxidation and as an artist's pigment because of its bright blue color.
A Co3+ ion is at the center of cyanocobalamin (vitamin B12), which is synthesized only by microorganisms and is not found in plants. Common dietary sources are fish, eggs, chicken, pork, and seafood. A diet deficient in cyanocobalamin results in pernicious anemia. Hydroxocobalamin, a Co3+-containing precursor to cyanocobalamin, is used as an antidote for cyanide poisoning (see Antidotes in Depth A40: Hydroxocobalamin).
Historically, cobalt chloride was combined with iron salts and marketed in the 1950s as "Roncovite" for the medical treatment of anemia. As recently as 1976, physicians still used cobalt to reduce transfusion requirements in anemic patients despite concomitant adverse effects.35 The other common medical use of cobalt is as a radioactive isotope, cobalt-60 (60Co). This γ emitter was formerly used in the radiotherapy of cancers but has been largely replaced by linear accelerators in the Western world. It may also be targeted by terrorist groups as a source of radioactive material.
Epidemics of cardiomyopathy and goiter termed "beer drinker's cardiomyopathy"12 and "cobalt-induced goiter"59 occurred in the 1960s and 1970s. During this period, cobalt sulfate was added to beer as a foam stabilizer. In the 1970s, these epidemics were halted with the discontinued utilization of cobalt for this purely aesthetic purpose.92
Current sources of cobalt exposure include chemistry kits,64 weather indicators,64 antiquated anemia therapies,64 cement,71 fly ash,71 mineral wool,71 asbestos,71 molds for ceramic tiles,41...