Excerpt from Volckens, J. "Mist Concentration Measurements: An Evaluation of Sampling Methods." Master's Thesis. UNC Chapel Hill, Dept. of Environmental Sciences and Engineering, School of Public Health. 1999.
Metalworking fluids are industrial lubricants used to enhance metalworking processes. Traditional metalworking operations include turning (lathe), grinding, drilling, and milling. During these operations, metalworking fluids are applied to cool, clean, and lubricate the interaction between tool and workpiece. In addition, these fluids inhibit corrosion of tools and workpieces. Metalworking fluids provide for more precise machining tolerances and longer tool lives and are thus invaluable to the metalworking industry. Unfortunately, mists formed from the application of these fluids have been associated with a variety of adverse health effects.(1-3) Therefore, various strategies have been employed to sample these mists to estimate occupational exposures.
The purpose of this research was to compare the efficiency of several conventional samplers when sampling metalworking fluid mists. Included in this report are two manuscripts that describe laboratory and field measurements of mineral oil, soluble oil, synthetic, and semi-synthetic fluid mists.
The first manuscript, "Oil mist concentration: a comparison of sampling methods," describes experiments performed with mineral oil mist. This manuscript was immediately submitted for publication upon completion due to its relevancy in the promulgation of a new federal standard regarding occupational exposure to oil mists. It was published in the Journal of the American Industrial Hygiene Association.
The second manuscript, entitled "Mist concentration measurements II: Laboratory and field evaluations," describes further experiments performed with synthetic fluid, semi-synthetic fluid, soluble oil, and straight oil. This manuscript was published in Applied Occupational and Environmental Hygiene.
Volckens, J., M. Boundy, D. Leith, and D.
Hands. Oil Mist Concentration: A Comparison of Sampling
J. 60: 684-689. (1999)
Discrepancies arise when sampling mineral oil mist using a glass fiber filter, a PVC filter, a PTFE filter, an electrostatic precipitator, and two light scattering devices. Most gravimetric methods show discrepancies because mist droplets, which have a high surface area, evaporate from the filters during sampling. Inconsistencies occur with light scattering devices because these instruments are sensitive to particle size distributions, shapes, and refractive indices. Results from laboratory and field experiments show that concentrations measured using these methods vary by factors of two to five. Discrepancies were greatest when oil mist concentrations were relatively low.
Volckens, J., M. Boundy, and D.
Leith. Mist Concentration Measurements II: Laboratory and Field
Occ. & Environ. Hyg. 15(4): 370 - 379. (2000)
Sampling methods to determine occupational exposures to metalworking fluid mists are subject to bias. Light scattering devices may respond differently to variations in particle size, shape, and refractive index. Gravimetric samplers are prone to evaporative losses of semi-volatile components. The performance of two light scattering devices, an electrostatic precipitator, and filters followed by gravimetric analysis was investigated when measuring metalworking fluid mist in laboratory and field settings. Laboratory tests with soluble oil and field tests with soluble oil, straight oil, and semi-synthetic fluid showed significant evaporative losses from filters. Light scattering devices tended to overestimate mist concentrations when mass median diameters were less than about 2 Ám and underestimate mist concentrations when mass median diameters were larger. Filters will underestimate occupational exposures to metalworking fluid mists when semi-volatile components are present.
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