title: How reliable are crystalline silica dust concentration measurements?
abstract: To determine how reliably commercial laboratories measure crystalline silica concentrations corresponding to OSHA's proposed limits, 105 filters were prepared with known masses of 20, 40, and 80 μg of respirable quartz corresponding to airborne silica concentrations of 25, 50, and 100 μg/m(3) and were submitted, in a blind test, to qualified commercial laboratories over a nine month period. Under these test conditions, the reported results indicated a lack of accuracy and precision needed to reliably inform regulatory compliance decisions. This was true even for filters containing only silica, without an interfering matrix. For 36 filters loaded with 20 or more micrograms of silica, the laboratories reported non-detected levels of silica. Inter-laboratory variability in this performance test program was so high that the reported results could not be used to reliably discriminate among filters prepared to reflect 8-h exposures to respirable quartz concentrations of 25, 50 and 100 μg/m(3). Moreover, even in intra-laboratory performance, there was so much variability in the reported results that 2-fold variations in exposure concentrations could not be reliably distinguished. Part of the variability and underreporting may result from the sample preparation process. The results of this study suggest that current laboratory methods and practices cannot necessarily be depended on, with high confidence, to support proposed regulatory standards with reliable data.
authors.affiliation: Cox Associates and University of Colorado, 503 Franklin St, Denver, CO 80218, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Cox
authors.affiliation: RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA 15146, USA. Electronic address: drew@rjlg.com.
authors.forename: D R
authors.initials: DR
authors.lastname: Van Orden
authors.affiliation: RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA 15146, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Lee
authors.affiliation: RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA 15146, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Arlauckas
authors.affiliation: RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA 15146, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Kautz
authors.affiliation: RJ Lee Group, Inc., 350 Hochberg Road, Monroeville, PA 15146, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Warzel
authors.affiliation: Vulcan Materials Company, 1200 Urban Center Drive, Birmingham, AL 35242, USA.
authors.forename: K F
authors.initials: KF
authors.lastname: Bailey
authors.affiliation: Sandler Occupational Medicine Associates, Inc., 12700 Sunrise Valley Dr, Suite 405, Reston, VA 20191, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Ranpuria
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis; D004391:Dust / Q000032:analysis*; D019570:Inhalation Exposure / Q000032:analysis; D016273:Occupational Exposure / Q000032:analysis; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D000395:Air Pollutants, Occupational; D004391:Dust; D012822:Silicon Dioxide
keywords: Crystalline silica; Interlaboratory testing; Intralaboratory testing; Precision; Variability; X-ray diffraction