In-Depth Lab Report: Laboratory Evaluation of Angle Grinder Discs for Grinding and Cutting Engineered Stone

Details

• Personal Author:
  Thompson, Drew ; Ku, Esther ; Qi, Chaolong
• Description:
  Background: Workplace exposure to respirable crystalline silica (RCS) can cause silicosis, a progressive lung disease marked by scarring and thickening of the lung tissue. Crystalline silica is found in several materials, such as brick, block, mortar, and concrete. Construction and manufacturing tasks that cut, break, grind, abrade, or drill those materials have been associated with overexposure to dust containing RCS. Stone countertop products can contain various levels of crystalline silica (can be >90 wt%) and working with this material during stone countertop fabrication has been shown to cause excessive RCS exposures. NIOSH scientists conducted a study to develop a control strategy for workers' RCS exposure during stone countertop fabrication. The laboratory research described in this report is part of that study. Assessment: NIOSH scientists systematically characterized the airborne dust generated from grinding and cutting an engineered stone product using a laboratory testing system designed and operated to collect representative respirable dust samples. The laboratory experiments in this study determined crystalline silica content, respirable dust and RCS generation rates, and dust size distributions during dry grinding using an angle grinder with fine, medium, and coarse grit grinding cup wheels and during dry cutting with a cutting blade. Results: There was no statistically significant difference in the mean crystalline silica content of the respirable dust generated by each angle grinder disc. The mean normalized generation rates of respirable dust and RCS were highest for the fine grit grinding cup wheel, followed in decreasing order by the medium grit grinding cup wheel, the coarse grit grinding cup wheel, and, finally, the cutting blade. The operation of the cutting blade and all grinding cup wheels generated mass-based size distributions with their most prominent mode located at an aerodynamic diameter of about 4.7 - 6.8 µm, with the mode increasing in size with increasing grit coarseness for the grinding cup wheels and being highest for the cutting blade. Conclusions and Recommendations: When removing the same volume of engineered stone by grinding or cutting activities, workers are likely to be exposed to lower quantities of RCS when cutting with a cutting blade, followed by grinding with a coarse grit grinding cup wheel, then grinding with a medium grit grinding cup wheel, and, finally, grinding with a fine grit grinding cup wheel. This suggests that an appropriate administrative control could be to train workers to prioritize cutting over grinding, when feasible, and when grinding prioritize grinding cup wheels with coarser grits whenever suitable for the surface finish required. This approach likely aligns with the workflow already used by most stone countertop fabricators, as it also maximizes the workpiece removal rate-a measure of process productivity. Description provided by NIOSH
• Subjects:
  • Dusts
  • Occupational Health
  • Safety
  • Silicon Dioxide
• Keywords:
  • Crystalline silica; Airborne dusts; Grinding equipment; Stone products; Control methods; Respirable dust; Countertops; Cutting tools; Administrative controls
• Source:
  Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB Report No. 2025-DFSE-2042, 2025 May; :1-34
• DOI:
  10.26616/NIOSHEPHB2025DFSE2042
• Document Type:
  Text
• Genre:
  Field Study
• Place as Subject:
  Chicago Region OSHA ; Ohio
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DFSE - Division of Field Studies and Engineering
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  40 pdf pages
• NIOSHTIC Number:
  nn:20071681
• CAS Registry Number:
  • Quartz (SiO2) (CAS RN 14808-60-7)
• Federal Fiscal Year:
  2025
• NORA Priority Area:
  Construction ; Manufacturing
• Peer Reviewed:
  False
• Download URL:
  https://stacks.cdc.gov/view/cdc/259452/cdc_259452_DS1.pdf
• File Type:
  [PDF - 1.17 MB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:81ffcdf362b800e48c185a36038ba111f7b5f4fbdc0ffd98d6f0788aabd77ed353b4f60672e91d8e2942f92cce566e6026e14d641f1d1a50339e10b85309d3f9