94: Cobalt

HISTORY AND EPIDEMIOLOGY

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 of exposure to arsenic rather than 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 Da, cobalt is a light metal with a melting point of 1768.2°K and a boiling point of 3373°K. These attributes make elemental cobalt (Co⁰) very useful in industry, where it is primarily incorporated into 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 due to 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 (Antidotes in Depth: A41).

Medicinally, cobalt chloride was combined with iron salts and marketed in the 1950s as “Roncovite”—for the treatment of anemia due to its ability to stimulate erythropoiesis. As recently as 1976, physicians still used cobalt salts to reduce transfusion requirements in anemic patients, despite well-known adverse effects.⁴³ The other common medical use of cobalt is as a radioactive isotope, cobalt-60 (⁶⁰ Co). This γ emitter was formerly used in the radiotherapy of cancers but has been largely replaced by linear accelerators in the Western world. Radiotherapy machines may be targeted by terrorist groups as a source of radioactive material.

Epidemics of cardiomyopathy and goiter termed “beer drinker’s cardiomyopathy”¹⁶ and “cobalt-induced goiter”⁶⁹ occurred between the 1960s and the 1970s. During this period, cobalt sulfate was added to beer as a foam stabilizer. In the 1970s, these epidemics were halted with the discontinued use of cobalt sulfate for this purely esthetic purpose.¹⁰⁶

Current sources of cobalt exposure include chemistry kits,⁷⁴ weather indicators,⁷⁴ antiquated anemia therapies,⁷⁴ cement,⁸¹ fly ash,⁸¹ dyes,⁵³ mineral wool,⁸¹ asbestos,⁸¹ molds for ceramic tiles,⁴⁹ the production of Widia-steel (utilized in the wood industry),¹⁴² mining,⁷⁵ porcelain paint,¹²⁶ orthopedic implants,⁷³ and dental hardware.⁷ A recent area of attention is “arthroprosthetic cobaltism,”^{97,115,130,156,157} which results from cobalt-containing orthopedic implants.¹⁵⁸

The most significant source, however, arises through the formation of cemented tungsten carbide, a “hard ...