Respirable silica dust suppression during artificial stone countertop cutting.
Cooper JH; Johnson DL; Phillips ML
Ann Occup Hyg 2015 Jan; 59(1):122-126
Purpose: To assess the relative efficacy of three types of controls in reducing respirable silica exposure during artificial stone countertop cutting with a handheld circular saw. Approach: A handheld worm drive circular saw equipped with a diamond segmented blade was fitted with water supply to wet the blade as is typical. The normal wetted-blade condition was compared to (i) wetted-blade plus 'water curtain' spray and (ii) wetted-blade plus local exhaust ventilation (LEV). Four replicate 30-min trials of 6-mm deep, 3-mm wide cuts in artificial quartz countertop stone were conducted at each condition in a 24-m3 unventilated tent. One dry cutting trial was also conducted for comparison. Respirable cyclone breathing zone samples were collected on the saw operator and analyzed gravimetrically for respirable mass and by X-ray diffraction for respirable quartz mass. Results: Mean quartz content of the respirable dust was 58.5%. The ranges of 30-min mass and quartz task concentrations in mg m-3 were as follows - wet blade alone: 3.54-7.51 and 1.87-4.85; wet blade + curtain: 1.81-5.97 and 0.92-3.41; and wet blade + LEV: 0.20-0.69 and <0.12-0.20. Dry cutting task concentrations were 69.6mg m-3 mass and 44.6mg m-3 quartz. There was a statistically significant difference (a = 0.05) between the wet blade + LEV and wet blade only conditions, but not between the wet blade + curtain and wet blade only conditions, for both respirable dust and respirable silica. Conclusions: Sawing with a wetted blade plus LEV reduced mean respirable dust and quartz task exposures by a factor of 10 compared to the wet blade only condition. We were unable to show a statistically significant benefit of a water curtain in the ejection path, but the data suggested some respirable dust suppression.
Silica-dusts; Respirable-dust; Stone-processing; Quartz-dust; Dust-control; Dust-exposure; Control-methods; Engineering-controls; Control-technology;
Author Keywords: countertop cutting; engineering controls; respirable silica
David L. Johnson, Department of Occupational and Environmental Health, University of Oklahoma College of Public Health, 801 NE 13th Street, Oklahoma City, OK 73104, USA
Annals of Occupational Hygiene
University of Oklahoma Health Sciences Center - Oklahoma City