Analysis of dusts and evaluation of dust exposure in a hard metal factory.

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Abstract
Dusts produced in different working areas of a hard metal workshop in the machinery factory were analyzed by an energy dispersive X-ray (EDX) microanalyzer, X-ray diffractometer and atomic absorption spectrophotometer (AAS). Cobalt excretion in the urine of workers was also analyzed by AAS. The raw material used for hard metal production was a mixed powder of metal cobalt and tungsten carbide. Almost all of the powder particles were of respirable size. The dust produced in the grinding process was also a combination of metal cobalt and tungsten carbide. Its size, shape and chemical composition were very similar to the raw material powder. The airborne dust in the workshop was less than 3 .mu.m in diameter. The chemical nature of cobalt and tungsten and the ratio of the two metals in the airborne dust was similar to those of the grinding dust and the raw material powder. Thus, there was no essential difference in the physical and chemical nature of the dusts produced in different working areas. These results supported the idea that urinary cobalt excretion could be used as a biological indicator of hard metal dust exposure. Urinary cobalt excretion showed an association with environmental cobalt exposure even when the exposure level was below 0.05 mg/m3. Thus, urinary cobalt excretion is sensitive enough to be used as a biological indicator in a modern factory where hard metal dust exposure is well controlled.