In 1988, the National Institute for Occupational Safety and Health (NIOSH) concluded that substantial evidence exists for an increased risk of several cancer types (larynx, rectum, pancreas, skin, scrotum, and bladder) among workers exposed to MWFs prior to the mid-1970s. MWFs have been the subject of a number of occupational epidemiologic studies of various types of cancer, non-cancerous respiratory conditions, and skin diseases. They are extensively used in the metalworking industry to lubricate, cool the tool-workpiece interface, and remove debris from the work surfaces of metal parts that are being drilled, ground, milled, or turned in various metalworking operations such as cutting, grinding, and metal-forming. Metalworking fluids (MWFs) are generally classified into four types (straight, soluble, synthetic and semi-synthetic) according to the amount and type of oil that they contain. The absence of an OEL for the water-soluble fluids used in approximately 80-90 % of all applicants may result in limitations of the protection from health risks caused by exposure to those fluids. Although adoption of The National Institute for Occupational Safety and Health's recommended exposure limit for MWF aerosol (0.5 mg/m 3) would be an effective step towards minimizing and evaluating the upper respiratory irritation that may be caused by neat or diluted MWF, this would fail to address the hazards (e.g., asthma and hypersensitivity pneumonitis) caused by microbial contaminants generated only by the use of water-soluble fluids. Particularly, the health risks from exposure to water-soluble fluids may not have been sufficiently considered. The OEL, is also based on the assumption that there are no significant differences in risk among fluid types, which may be contentious. The OEL (time-weighted average 5 mg/m 3, short-term exposure limit 15 mg/m 3) has been applied to MWF aerosols without consideration of different fluid aerosol-size fractions. The aim of this review was to assess current knowledge related to the occupational exposure limit (OEL) for fluid aerosols including either mineral or chemical oil that are generated in metalworking operations, and to discuss whether their OEL can be appropriately used to prevent several health risks that may vary among metalworking fluid (MWF) types.

Timetable chart for mist exposure