Last data update: Sep 16, 2024. (Total: 47680 publications since 2009)
Records 1-2 (of 2 Records) |
Query Trace: Key-Schwartz RJ [original query] |
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Preparation of respirable crystalline silica samples for subsequent analysis
Harper M , Key-Schwartz RJ . Regul Toxicol Pharmacol 2016 83 100-102 We respectfully disagree with the conclusion in the paper by Lee, R.J. et al. (2016) that: “… muffle furnace preparation of [respirable crystalline] silica samples be discontinued” because the authors data and the results of previously published studies do not support this assertion. Muffle furnace treatment and low-temperature plasma ashing are regarded as equivalent sample preparation steps for respirable crystalline silica analysis in NIOSH Manual of Analytical Methods 7500 (NIOSH, 2003a) and 7602 (NIOSH, 2003b). Muffle furnace ashing is also used for sample preparation in several international standard methods (ASTM International, 2014; HSE, 1984; INSHT, 2005; INS, 2013; ISO, 2015). A previously published study by Cox et al. (2015) obtained results that indicated “under-reporting” of silica mass on test filters. Lee, R.J. et al. (2016) examines two possible reasons, “shipping” and “level of effort”, as to why results were low in the Cox et al. study. Although Lee, R.J. et al. (2016) correctly state that “OSHA (2016) reviewed the Cox et al. study and identified several deficiencies associated with filter generation and quality control testing that OSHA believes invalidates the Cox et al. findings”, they follow this with the statement that their study “addresses OSHA’s comments and finds the deficiencies cited did not contribute to the results of the Cox study”. This latter statement is surprising in that the major deficiency noted by OSHA in their criticism of the Cox et al, (2015) study involved “filter generation and quality control testing”, not “shipping” or “level of effort”. |
Consideration of kaolinite interference correction for quartz measurements in coal mine dust
Lee T , Chisholm WP , Kashon M , Key-Schwartz RJ , Harper M . J Occup Environ Hyg 2013 10 (8) 425-34 Kaolinite interferes with the infrared analysis of quartz. Improper correction can cause over- or underestimation of silica concentration. The standard sampling method for quartz in coal mine dust is size selective, and, since infrared spectrometry is sensitive to particle size, it is intuitively better to use the same size fractions for quantification of quartz and kaolinite. Standard infrared spectrometric methods for quartz measurement in coal mine dust correct interference from the kaolinite, but they do not specify a particle size for the material used for correction. This study compares calibration curves using as-received and respirable size fractions of nine different examples of kaolinite in the different correction methods from the National Institute for Occupational Safety and Health Manual of Analytical Methods (NMAM) 7603 and the Mine Safety and Health Administration (MSHA) P-7. Four kaolinites showed significant differences between calibration curves with as-received and respirable size fractions for NMAM 7603 and seven for MSHA P-7. The quartz mass measured in 48 samples spiked with respirable fraction silica and kaolinite ranged between 0.28 and 23% (NMAM 7603) and 0.18 and 26% (MSHA P-7) of the expected applied mass when the kaolinite interference was corrected with respirable size fraction kaolinite. This is termed "deviation," not bias, because the applied mass is also subject to unknown variance. Generally, the deviations in the spiked samples are larger when corrected with the as-received size fraction of kaolinite than with the respirable size fraction. Results indicate that if a kaolinite correction with reference material of respirable size fraction is applied in current standard methods for quartz measurement in coal mine dust, the quartz result would be somewhat closer to the true exposure, although the actual mass difference would be small. Most kinds of kaolinite can be used for laboratory calibration, but preferably, the size fraction should be the same as the coal dust being collected. |
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