COBALT EXPOSURE IN WET GRINDING OF HARD METAL TOOLS FOR WOOD MANUFACTURE

The authors examined exposure to cobalt during the wet grinding of har d metal tools (Widia tools) used in the wood industry, usually in smal l specialized workshop which can produce exposure to cobalt >TLV-TWA ( 50 mug/m3) if carried out with no protective devices. Local exhausts n ear the grinding wheel can reduce the exposure to cobalt by as much as 20 times. Nevertheless, some technical problems often hamper the effe ctiveness of these protective devices, so that the plant situation, ex amined by the forecasting OTL test as proposed by Tuggle (Am. Ind. Hyg . Assoc. J., 43 (1982) 338), does not appear to be completely acceptab le. Other technical solutions are therefore necessary for a complete c ontrol of the exposure to cobalt. A more effective water stream, a gre ater air velocity near the grinding wheel and a protective shield betw een the wheel and the worker are some suggestions.