Exposure assessment in the hard metal manufacturing industry with special regard to tungsten and its compounds

Objectives-To assess the exposure to tungsten, cobalt, and nickel in a plan t producing hard metals. The main components of hard metals are tungsten ca rbide and cobalt metal. According to recent studies, these two components m ay be responsible for both fibrogenic and carcinogenic effects. Methods-87 workers were investigated (86 male, one female) with a median ag e of 42 (range 22-58) and a mean duration of exposure of 13 years (range 1- 27 years). Stationary and personal air sampling, and biological monitoring were carried out. Results-Ambient monitoring yielded maximum tungsten concentrations of 417 m ug/m(3) in the production of heavy alloys. A maximum cobalt concentration o f 343 mug/m(3) and a maximum nickel concentration of 30 mug/m(3) were found at the sintering workshop. The highest urinary cobalt concentrations were found in the powder processing department. The mean concentration was 28.5 mug/g creatinine and the maximum value was 228 mug/g creatinine. The maximu m nickel concentration in urine of 6.3 mug/g creatinine was detected in the department producing heavy alloys. The highest tungsten concentrations exc reted in urine were found in grinders and had a mean value of 94.4 mug/g cr eatinine and a maximum of 169 mug/g creatinine. Due to the different solubi lity and bioavailability of the substance, there was no correlation between the tungsten concentrations in air and urine on a group basis. Conclusions-Despite its low solubility, tungsten carbide is bioavailable. T he different bioavailability of tungsten metal and tungsten compounds has t o be considered in the interpretation of ambient and biological monitoring data in the hard metal producing industry. The bioavailability increases in the order: tungsten metal, tungsten carbide, tungstenate. Only if both mon itoring strategies are considered in combination can a valid and effective definition of high risk groups be derived.