Exposure to coolant mists produced by metal machining operations has long been associated with occupational disease. In recent years, evidence linking exposure to coolant mists with cancers of the gastrointestinal tract have led to calls for a substantial lowering of the PEL for these mists: from 5.0 to 0.5 mg/m3. To achieve these levels, effective controls are crucial. At present, mist control is accomplished by ventilation of the mist- producing process, then collection of the mist from the ventilation air. Another control method, potentially even more effective than ventilation and collection, is to reduce the generation of these mists at the source. Reducing mist generation requires knowledge of the factors that affect the generation rate and size distribution of these mists. This proposal is for a fundamental investigation of factors that affect the generation of coolant mists. This research will characterize how metal turning and metal grinding operations generate coolant mists. Experiments will be conducted in which mist generation rates and size distributions will be characterized for both processes over a range of operating conditions. Results will be analyzed through dimensionless groups that characterize process characteristics such as surface velocity, process power, and coolant flow, and fluid characteristics such as viscosity and surface tension. The results of this research will be presented in equations that predict mist generation rate and size distribution. These equations will suggest how machining processes and the properties of coolant fluids might be altered to reduce mist generation. They may also be useful to help characterize past mist exposures for epidemiological studies where exposure measurements were not made or were incomplete.
