A Comparison of Two Methods of Sampling and Analysis for Free Crystalline Silica α-Quartz

Two methods of sampling and analysis for silica (free crystalline silica α-quartz) were compared, using samples collected in an underground gold-mining environment. Ten airborne respirable dust sampling systems were set up and run simultaneously at varied locations (ore pass, drifts, and stopes) and tasks in an area sampling program. Five sampling systems complied with the method recommended by the Ontario Ministry of Labour (OML), and five followed the U.S. National Institute for Occupational Safety and Health (NIOSH) Method 7602. Ground Ottawa Silica Sand[rgrave] is used as the calibration standard for X-ray diffraction in the OML method, and Min-U-Sil 5[rgrave] or NBS-SRM 1878 silica is used as the calibration standard in NIOSH 7602 Infrared Spectrophotometric Method. A total of 274 long-term (6- to 7-h duration) samples were collected. The silica concentration measured by the OML method showed a statistically significant positive bias of about 24–30 percent compared to NIOSH Method 7602. The results of silica concentrations given by the two methods become equivalent when Ottawa Silica Sand is used as the calibration standard in both. Verma, D.K.; Sebestyen, A.; Julian, J.A.; Muir, D.C.F.: A Comparison of Two Methods of Sampling and Analysis for Free Crystalline Silica α-Quartz. Appl. Occup. Environ. Hyg. 7(11):758–763; 1992.