Last data update: Jun 03, 2024. (Total: 46935 publications since 2009)
Records 1-6 (of 6 Records) |
Query Trace: Key-Schwartz R [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”. |
Analysis of crystalline silica in bulk materials
Harper M , Key-Schwartz R . Ann Occup Hyg 2014 58 (5) 657-8 We are writing concerning results presented in Annals of Occupational Hygiene as part of a manuscript by Radnoff and Kutz (2014). The manuscript presents the results of seven analyses without associated uncertainty or validated Limit of Quantitation (LOQ) for bulk crystalline silica content with values reported <1% down to <0.1%. In the Methods section, they state the samples were ‘analysed according to NIOSH Method 7500 for the presence of quartz silica down to 0.1% w/w. This method includes protocols for analysing bulk or settled dust samples’. The NIOSH 7500 method (NIOSH, 2003) is designed to quantify respirable samples collected on a filter and does not include specific procedures for analyzing bulk or settled dust samples beyond using bulk samples to identify interferences in the air samples. The user of the method is directed from Paragraph 4a: Interference check. Prepare area dust sample or settled dust bulk sample for XRD analysis … to Paragraph 11: Obtain a qualitative X-ray diffraction scan of the area air sample (or bulk settled dust) to determine the presence of free silica polymorphs. The subsequent quantitative section (Paragraph 12) refers only to the air sample filter analysis. No evaluation data or LOQ estimate are presented in NIOSH 7500 to support bulk analysis and it is unlikely that the method could be used to measure down to or <0.1% in any case. | Verma et al. (2002) evaluated an infrared method for bulk analysis between 1 and 75% and concluded that although it could be used to determine down to 1% in routine analyses, the method was ineffective <1% silica. A more recent evaluation of an X-ray diffraction method (Martin et al., 2012) suggests that it may be very difficult to go much <1%, even with the additional use of the Rietveld refinement in X-ray diffraction (LOQ = 0.76%). We are unaware of any method that has been published for the determination of crystalline silica in bulk materials that can measure down to 0.1%. If the laboratory used by Radnoff and Kutz has been able to modify NIOSH 7500 to achieve this goal, we would welcome publication of the details of the modification and methods validation as this would be of value to the occupational health community. |
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. |
NIOSH Manual of Analytical Methods 5th Edition-new resources and direction
Schlecht P , O'Connor PF , Key-Schwartz R , Lunsford A , Gagnon Y . J Occup Environ Hyg 2011 8 (7) 59-62 In 1973, the National Institute for Occupational Safety and Health (NIOSH) published the first edition of the NIOSH Manual of Analytical Methods (NMAM®). It contained 38 procedures developed by chemists at NIOSH. Today, the NMAM is accessible on the Internet at http://www.cdc.gov/niosh/docs/2003-154/ and contains more than 300 methods. | The NMAM, a compendium of validated methods for measuring occupational exposures to hazardous substances, is one of the most successful products in NIOSH history. The current fourth edition( Citation1 ) is the second most visited and downloaded document on the NIOSH website (receiving an average 30,000 visits per month, 60% of these international; Figure 1 shows the distribution by region.) The methods most often downloaded are shown in Figure 2, with metals, hydrocarbons, and particulates comprising the top three. |
An Evaluation of Aerosol- and Liquid-Generated Silica Samples for Proficiency Analytical Testing
Hayes T , Parish H , Key-Schwartz R , Popp D . J ASTM Int 2006 3 (6) SRI International has prepared dynamically generated silica samples since 1980 for the National Institute of Occupational Safety and Health (NIOSH) and the American Industrial Hygiene Association (AIHA) Proficiency Analytical Testing (PAT) programs. Aerosol-generated samples were developed in 1980 to more closely approximate real world samples and to improve intrabatch precision. Liquid-generated samples may provide tighter control limits, and this method has been reexamined as the generation procedure of choice. Sample preparation procedures have also been investigated to minimize analytical uncertainty and, hence, obtain a true evaluation of the sampling error. Samples were analyzed by SRI, NIOSH, and the Wisconsin Occupational Health Laboratory, using X-ray diffraction or Fourier transform infrared spectrometry (FTIR). Results were plotted and statistically evaluated, then compared to the existing PAT interlaboratory database. |
An International comparison of the crystallinity of calibration materials for the analysis of respirable alpha-quartz using X-ray diffraction and a comparison with results from the infrared KBr disc method
Stacey P , Kauffer E , Moulut JC , Dion C , Beauparlant M , Fernandez P , Key-Schwartz R , Friede B , Wake D . Ann Occup Hyg 2009 53 (6) 639-49 It is important that analytical results, produced to demonstrate compliance with exposure limits are comparable, to ensure controls are monitored to similar standards. Correcting a measurement result of respirable alpha-quartz for the percentage of crystalline material in the calibration dust is good analytical practice and significant changes in the values assigned to calibration materials will affect the interpretation of results by an analyst or occupational hygiene professional. The reissue of the certification for the quartz reference material NIST 1878a in 2005 and differences in comparative values obtained by other work created uncertainty about the values of crystallinity assigned to national calibration dusts for alpha-quartz. Members of an International Organization for Standardization working group for silica measurement ISO/TC146/SC2/WG7 collaborated to investigate the comparability of results by X-ray diffraction (XRD) and to reach a consensus. This paper lists the values recommended by the working group for use with XRD analysis. The values for crystallinity obtained for some of the materials (NIST 1878, Min-U-Sil5 and A9950) were 6-7% lower than the original certification or estimates reported in other comparisons. Crystallinity values obtained by XRD gave a good correlation with BET surface area measurements (r2 = 0.91) but not with mean aerodynamic particle size (r2 = 0.31). Subsamples of two of the materials (A9950 Respirable and Quin 1 Respirable) with smaller particle size distribution than their parent material did not show any significant change in their values for crystallinity, suggesting that the area XRD measurement of these materials within the particle size range collected is more dependent on how the quartz is formed geologically or how it is processed for use. A comparison of results from laboratories using the infrared (IR) and KBr disc method showed that this method is more dependent than XRD on differences in the particle size within the respirable size range, whereas the XRD values were more consistent between the different measurement values obtained on each material. It was not possible to assign a value for percentage purity to each material for users of IR analysis. This work suggests that differences are likely to exist between the results from XRD and IR analysis when measuring 'real' workplace samples and highlights the importance of matching the particle size of the calibration material to the particle size of the workplace dust for measurements of crystalline quartz. |
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