Impact of muffle furnace preparation on the results of crystalline silica analysis.
A prior report demonstrated an unacceptably low level of accuracy in silica analytical testing, with a general negative bias (i.e., underreporting) although other inaccuracies included false-positive results when analyzing blank filters. The possible bias may have been due to the loss of sample during shipping and or sample preparation. We report on a follow-up study that was designed to mimic the original study, but in which sources of variability were evaluated. We found no effect on silica recoveries due to shipping and confirmed the prior study results that the muffle furnace ashing process led to low overall recoveries (49-104%), depending on the adherence to the recommended preparation method. Plasma ashing recoveries ranged from 89 to 108%. Our results suggest that muffle-furnace ashing using a crucible should be restricted. More broadly, however, muffle-furnace ashing is only one source of analytical error that contributes to the relatively poor overall performance revealed by Cox et al. Whatever the case, OSHA should ensure that its proposed requirements to improve laboratory performance will actually lead to the discovery and correction of all major sources of error by participating laboratories. This is particularly important in light of OSHA's proposed reduction in the PEL and action level proposed by OSHA.
RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA, 15146, USA.
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RJ
Lee
RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA, 15146, USA. Electronic address: drew@rjlg.com.
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Van Orden
Cox Associates Inc., 503 Franklin Street, Denver, CO, 80218, USA.
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LA
Cox
RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA, 15146, USA.
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Arlauckas
RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA, 15146, USA.
R J
RJ
Kautz
D003460:Crystallization; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D006358:Hot Temperature; D006801:Humans; D017745:Incineration / Q000295:instrumentation*; D019570:Inhalation Exposure / Q000009:adverse effects; D015233:Models, Statistical; D016273:Occupational Exposure / Q000009:adverse effects; D016272:Occupational Health; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012822:Silicon Dioxide / Q000009:adverse effects / Q000032:analysis*
D052638:Particulate Matter; D012822:Silicon Dioxide
Crucible; Crystalline silica; Muffle furnace; NIOSH 7500; Plasma ash; X-ray diffraction