Determinants of Respirable Silica Exposure in Stone Countertop Fabrication: A Preliminary Study

Abstract

A preliminary study of personal exposure to respirable quartz was conducted in four shops that used a variety of wet and dry methods to fabricate countertops from granite and quartz-containing synthetic stone-like materials. Full-shift time-weighted average (TWA) exposures exceeded the ACGIH threshold limit value of 0.025 mg/m³ for all workers who used dry fabrication methods, even for very limited time, during any part of the work shift (n = 15 person-days). The geometric mean of exposures for workers who used dry methods extensively was about 1 mg/m³ (n = 12 person-days). Workers who operated only automated or remotely controlled stone cutting or shaping equipment had calculated TWA exposures of approximately 0.02 mg/m³ (n = 3 person-days). Task-specific geometric mean exposures for various wet and dry manual operations were ranked based on estimated concentrations extracted from multi-task partial-shift sample results using a linear algebra procedure. Limited use of dry methods was observed in shops that had previously reported using only wet methods. These results suggest that even shops that report using only wet methods might, in fact, resort to brief use of dry methods for specific operations. Therefore, there may be reason for concern over potential overexposure to respirable quartz in all stone countertop shops.

Keywords:

• crystalline silica
• determinants of exposure
• granite dust
• task exposure

ACKNOWLEDGMENTS

This research was supported by a seed grant from the University of Oklahoma Health Sciences Center Vice President for Research and by NIOSH Training Grant 5T01OH0086 14. The authors thank Linda Kincaid for donation of preloaded filter cassettes; Kim Graziano, Anthony Banks, and Ishita Tejani for assistance in sample collection; and the owners and employees of the participating shops for their cooperation in this study.