Pulmonary toxicity of cobalt-containing dusts

Cobalt is a hard metal with magnetic properties, resembling iron or nickel. It is practically insoluble in water but dissolves readily in biological fluids like plasma. Ionic cobalt exists in either a bivalent or a trivalent form and different oxides and salts are encountered in the industry. Cobalt is an essential nutrient to humans with vitamin B12 representing the major physiological form in which cobalt functions in the body. Cobalt is mostly produced as a secondary product during the processing of other metals like copper, nickel and lead. The major sources of minerals are Zaire, Zambia, Canada and ex-USSR while the principal consumer of cobalt is the US which uses about 50% of the world production (Lison 1993).