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Qualitative methods for characterizing worker exposures in the metalworking fluid environment.

Lunsford RA; Pretty JR; Brown KK; Glaser RA; Arnold JE; Beck S
Working Partnerships: Applying Research to Practice, NORA Symposium 2003, June 23-24, 2003, Arlington, Virginia. Washington, DC: National Institute for Occupational Safety and Health, 2003 Jun; :91
Manufacturing processes involving the shaping or machining of metal often use metalworking fluids (MWFs) to assist in removal of debris and for cooling, lubrication, and protection of freshly exposed metal surfaces. Worker exposure to MWF aerosol has been associated with an increased risk for nonmalignant respiratory disease and skin diseases. In 1998, NIOSH published a recommended exposure limit (REL) for MWF aerosol of 0.4 mg per cubic meter of air for thoracic particulate mass (or 0.5 mg per cubic meter for total particulate mass). NIOSH Method 5524 was developed to provide quantitative measurement directly related to the NIOSH REL and a fundamental qualitative characterization of worker exposures to MWF aerosol, i.e., the differentiation between total sample mass and extracted mass. Thus far in field studies, all MWFs, as supplied by their manufacturers, have been fully extractable. Unextracted material in field samples may be attributable to non- MWF sources and subject to other health evaluation criteria. Examples from field studies of welding fume exposures are presented to show the benefits of having both measures of exposure. NIOSH researchers are currently investigating the application of gas chromatography-mass spectrometry (GCMS) and liquid chromatography-mass spectrometry (LC-MS) for the qualitative analysis of MWFs. GC-MS is a well established technique for identifying thermally stable volatile and semivolatile components of complex mixtures. Recent improvements in the sensitivity and ruggedness of liquid chromatography-mass spectrometry (LC-MS) instrumentation make it a promising tool for the identification of many thermally labile and nonvolatile compounds. The various MWFs commercially available may comprise hundreds of substances, including cationic and anionic surfactants; alkaline compounds, such as alkanolamines; polar neutrals, such as nonionic emulsifiers; acidic compounds, including fatty acids and phenols; and nonpolar compounds, such as mineral oils and chlorinated paraffins. Solid phase extraction and multimodal liquid chromatographic methods are being evaluated for their ability to fractionate MWF samples by chemical class. Class fractions and unfractionated MWF samples are analyzed by GC-MS and LC-MS to provide specific chemical identifications. Early results are very encouraging. Direct analysis by LC-MS has demonstrated, in a MWF matrix, specific identification of N-nitrosamines, including N-nitrosodiethanolamine (N-DELA) and N-nitrosomorpholine (NMORPH), and the biocide, hexahydro-1,3,5-tris (2-hydroxyethyl)-s-triazine. N-DELA and N-MORPH are potentially carcinogenic contaminants of MWF; the biocide has been associated with hypersensitivity pneumonitis. Methods developed for chemical characterization of the broad range of compounds present in MWF formulations will likely be directly applicable to other sample matrices. The development of these methods is expected to shed light on occupational exposures to a larger array of compounds, including nonvolatile and thermally labile compounds. Detailed knowledge of chemical composition is crucial to specific hazard identification and efficient intervention through product reformulation.
Metal-compounds; Metal-industry; Metal-industry-workers; Metal-workers; Respiratory-system-disorders; Skin-diseases; Gas-chromatography; Mass-spectrometry; Aerosols; Chemical-analysis; Chemical-composition; Analytical-methods
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NIOSH Division
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Research Tools and Approaches: Exposure Assessment Methods
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Working Partnerships: Applying Research to Practice, NORA Symposium 2003, June 23-24, 2003, Arlington, Virginia
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division