Objective To investigate the internal and external exposure levels of tungsten and cobalt in workers in tungsten alloy manufacturing enterprises, and analyze their distribution characteristics in order to provide data support for occupational health risk assessment of hard metal lung disease induced by tungsten alloy.
Methods Four tungsten alloy manufacturing enterprises of different sizes were selected, in which 489 workers exposed to tungsten and its alloys for more than one year were enrolled as exposure group by random sampling, and 325 workers without exposure as control group. Occupational health conditions of workplaces were investigated and the levels of airborne tungsten and cobalt were detected. The whole blood samples of the workers were collected to determine the tungsten and cobalt levels by in ductively coupled plasma mass spectrometry.
Results The exposure ranges of tungsten and cobalt in workplace air were < 0.03-4.42 mg/m3 (median, 0.11 mg/m3) and < 0.013-0.677 mg/m3 (median, 0.017 mg/m3), respectively. Wet-grinding, drying, sintering, machining, and product packaging workers had higher air cobalt exposure levels than corresponding national standard limits. In the exposed group, the positive blood tungsten rate was 12.5% (concentration, < 0.5-21.0 μg/L; median, < 0.5 μg/L), and the positive blood cobalt rate was 61.1% (concentration, < 0.5-15.7μg/L; median, 0.7μg/L), which were both higher than those in the controls (P < 0.01). There were significant differences in blood tungsten and cobalt levels between the workers with different types of job (P < 0.01). Blood tungsten was positively correlated with airborne tungsten (r=0.106, P < 0.05). Blood cobalt was also positively correlated with airborne cobalt (r=0.197, P < 0.01).
Conclusion The tungsten concentrations in workplace air meet the national health requirement, but the cobalt concentrations exceed the national standard limit. The tungsten and cobalt levels in blood are positively correlated with the airborne tungsten and cobalt levels respectively.
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