Cobalt exposure in wet grinding of hard metal tools for wood manufacture.

The authors examined exposure to cobalt during the wet grinding of hard metal tools (Widia tools) used in the wood industry, usually in small specialized workshop which can produce exposure to cobalt > TLV-TWA (50 micrograms/m3) if carried out with no protective devices. Local exhausts near the grinding wheel can reduce the exposure to cobalt by as much as 20 times. Nevertheless, some technical problems often hamper the effectiveness of these protective devices, so that the plant situation, examined by the forecasting OTL test as proposed by Tuggle (Am. Ind. Hyg. Assoc. J., 43 (1982) 338), does not appear to be completely acceptable. Other technical solutions are therefore necessary for a complete control of the exposure to cobalt. A more effective water stream, a greater air velocity near the grinding wheel and a protective shield between the wheel and the worker are some suggestions.