Work Practices and Respirable Crystalline Silica Exposures in Stone Countertop Fabrication Shops

Reports of silicosis among US workers who fabricate and install stone countertops are increasing. Our aim was to better characterize work processes, stone type, occupational health practices, and exposures to respirable crystalline silica (RCS) in this industry.

A survey was administered to stone countertop fabrication shops to assess shop characteristics, controls, and operations. Shops were asked to share past RCS air monitoring reports. We examined associations between RCS concentrations and stone type, similar exposure groups (SEG), and engineering controls in multivariate models, and RCS exposures by shop.

Of 257 shops surveyed, 98% reported processing both natural and engineered stone (ES), utilizing semi-automated equipment and small hand tools, and a variety of control methods. Only 42% of shops that required the use of a respirator reported conducting respirator fit testing, and only 19.5% performed medical surveillance. A total of 47% of shops reported RCS air sampling, with 38% submitting 292 RCS air samples used for this analysis. Overall, the RCS geometric mean (GM) was 14.1 μg/m³, with 75.7% of RCS samples below the US Occupational Safety and Health Administration (OSHA) action limit (AL). However, RCS levels were highly variable (range 2.8-5100.0 μg/m³), with 9.2% of RCS samples exceeding the OSHA permissible exposure limit (PEL), and 43.5% shops 1 or more samples above the OSHA AL. Use of small hand tools with no controls produced the highest RCS exposures, and dry work had significantly higher RCS exposures than any control method.

The findings underscore the extensive use of ES and the opportunity for overexposure to RCS in this industry. They highlight the need to eliminate dry processing methods, enhance respiratory protection, and perform repeated RCS sampling to monitor the effectiveness of controls. Additionally, more widespread medical surveillance is urgently needed to assess the extent of silicosis in this industry.