Chapter 91: Cobalt

INTRODUCTION

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 had more likely resulted from the arsenic exposure than that of the cobalt. Georg 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 that has a melting point of 1,768.2° K and a boiling point of 3,373° K. These attributes make elemental Co (Co⁰) very useful in industry, in which 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 owing 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 because of its ability to stimulate erythropoiesis. As recently as 1976, physicians still used cobalt salts to reduce transfusion requirements in anemic patients in spite of concomitant adverse effects.⁴⁷ The other common medical use of cobalt is as a radioactive isotope, cobalt-60 (⁶⁰Co). This gamma emitter was formerly used in the radiotherapy of cancers but was largely replaced by linear accelerators in the Western world. Radiotherapy devices are a source of radioactive material that could be used by terrorist groups.

Epidemics of cardiomyopathy and goiter termed “beer drinker’s cardiomyopathy”¹⁸ and “cobalt-induced goiter”^33,104 occurred between the 1950s and the 1970s. During that 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 aesthetic purpose.¹¹⁹

Current sources of cobalt exposure include chemistry sets,⁸⁰ weather indicators,⁸⁰ antiquated anemia therapies,⁸⁰ cement,⁸⁸ fly ash,⁸⁸ dyes,⁵⁶ mineral wool,⁸⁸ asbestos,⁸⁸ molds for ceramic tiles,⁵² the production of Widia-steel (utilized in the wood industry),¹⁵⁹ mining,⁸¹ porcelain paint,¹⁴⁰ orthopedic implants,⁷⁹ dental hardware,⁹ and as a nutritional supplement.¹⁷⁷ The most recent area of concern is “arthroprosthetic cobaltism,”^{109,128,145,175,176} which results ...