28927166

PMC5675121

Objectives

Workers who fabricate stone countertops using hand tools are at risk of silicosis from overexposure to respirable crystalline silica. This study explored the efficacy of simple engineering controls that can be used for dust suppression during use of hand tools by stone countertop fabricators.

Methods

Controlled experiments were conducted to measure whether wet methods and on-tool local exhaust ventilation (LEV) reduced respirable dust exposures during use of various powered hand tools on quartz-rich engineered stone. Respirable dust samples collected during edge grinding with a diamond cup wheel and a silicon carbide abrasive wheel were analyzed gravimetrically as well as by x-ray diffraction to determine silica content. A personal optical aerosol monitor was used simultaneously with the respirable dust samples and also for rapid assessment of controls for polishing, blade cutting, and core drilling.

Results

On-tool LEV and sheet-flow-wetting were effective in reducing exposures, especially when used in combination. Sheet-flow-wetting with LEV reduced geometric mean exposures by as much as 95%. However, typical water-spray-wetting on a grinding cup was less effective when combined with LEV than without LEV. Mean silica content of respirable dust samples from grinding operations was 53%, and respirable mass and silica mass were very highly correlated (r = 0.980). Optical concentration measures were moderately well correlated with gravimetric measures (r = 0.817), but on average the optical measures during a single trial using the factory calibration were only one-fifth the simultaneous gravimetric measures.

Conclusions

Sheet-flow-wetting combined with on-tool LEV is an effective engineering control for reducing respirable dust exposures during engineered stone edge grinding and blade cutting. On the other hand, addition of LEV to some water-spray-wetted tools may reduce the effectiveness of the wet method.

CDC Public Access

CC999999/Intramural CDC HHS/United States
T03 OH008614/OH/NIOSH CDC HHS/United States