Biological monitoring of workers exposed to cobalt metal, salt, oxides, and hard metal dust.

OBJECTIVE The aim was to examine the relation between environmental and biological (blood and urine) indices of exposure to different chemical forms of cobalt. METHODS A cross sectional study was undertaken in workers exposed to cobalt metal, oxides, and salts in a refinery and to a mixture of cobalt and tungsten carbide in a hard metal producing plant. RESULTS AND CONCLUSION Although biological monitoring of workers exposed to cobalt oxides showed higher blood and urine concentrations than in non-exposed subjects, these indices poorly reflected the recent exposure level. By contrast, when exposure was to soluble cobalt compounds (metal, salts, and hard metals), the measurement of urine or blood cobalt at the end of the workweek could be recommended for the assessment of recent exposure. An eight hour exposure to 20 or 50 micrograms/m3 of a soluble form of cobalt would lead to an average concentration in a postshift urine sample collected at the end of the workweek of 18.2 or 32.4 micrograms of cobalt/g creatinine, respectively.