Relationships among Fluid Ethanolamine Formulation, Airborne Ethanolamines, and Aerosol Levels in Machining Operations

Abstract

Alkanolamines or ethanolamines - triEA (TEA), di-EA (DEA), and mono-EA (MEA) - may be used in water-soluble metalworking fluids to stabilize pH or inhibit corrosion. The objectives of this study were to compare EAs levels from air and used fluid bulk among the various metalworking operations, and to examine the relationship not only between aerosol concentration and total airborne EA levels, but also between aerosol levels and the proportion of each type of EA in the total EA in air and fluid bulk. The EA from air and fluid bulk collected from machining operations were quantified by ion chromatography. Airborne EA were taken into de-ionized water (DI) using an impinger. Average aerosol levels were 1.15 mg/m3 for machining and 0.84 mg/m3 for grinding operations. The highest aerosol and total EA levels were for (i) washing operations (4.06 mg/m3 and 1.33 mg/m3, respectively), where compressed air was frequently used to clean metal machine parts, and (ii) individual tanks (1.83 mg/m3 and 2.31 mg/m3, respectively). Airborne MEA was detected in all samples (n = 53), while TEA was not detected in any air samples (n = 13) taken from areas without machining operations. Machining operations showed a significant relationship between aerosol and total EA levels (n = 21, R2 = 0.74). The EA content ratio (EAR: level of each EA in air as a% of total EA in air)/(level of each EA in bulk fluid as a% of total EA in bulk fluid) showed a significant association with the aerosol level, but showed a different pattern according to the EA type. A negative exponential relationship was observed for MEAR (n = 9, R2 = 0.64), with MEAR being greater than "1" at low aerosol concentrations (< 1 mg/m3). In contrast, TEAR increased linearly with increasing aerosol levels, reaching almost "1" when the aerosol concentration was higher than 2.0 mg/m3. The relationship between fluid EA formulation, airborne EA levels, and aerosol levels in machining operations was found to be quite different according to the type of EA. © Taiwan Association for Aerosol Research.