In-Depth Survey Report: Removing Mortar by Wet Grinders and Powered Chisels with On-Tool Local Exhaust Ventilation

Details

• Personal Author:
  Qi, Chaolong
• Corporate Authors:
  National Institute for Occupational Safety and Health. Division of Applied Research and Technology
• 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. Quartz is the most common form of crystalline silica. 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. Tuckpointing (repointing) removes damaged mortar from joints in masonry walls and replaces it with new mortar to restore the wall. The use of dry grinders to remove mortar results in worker overexposure to respirable crystalline silica. NIOSH researchers have been conducting a study to assess the RCS exposures associated with mortar removal when tools other than dry grinders are used. The site visit described in this report is part of that study. Assessment: A NIOSH researcher visited a jobsite at the Packer Memorial Church, Bethlehem, Pennsylvania between June 17 to 20, 2019, and performed industrial hygiene sampling, which measured exposures to respirable dust and RCS while three workers used wet grinders and powered chisels with on-tool local exhaust ventilation (LEV) to remove mortar from stone walls. The NIOSH researcher also observed the work process in order to understand the conditions that contributed to the measured exposure. Results: The time weighted average (TWA) RCS exposure ranged from 7.9 to 40.8 µg/m3 when using wet grinders, and from 6.0 to 15.1 µg/m3 when using powered chisels with the on-tool LEV. The workers' RCS exposures were well under control for both tools and their respective control measures. Excluding an outlier data point associated with wet grinders, the 95% upper confidence limit of the RCS exposure was 22.7 µg/m3 for using wet grinders and 11.5 µg/m3 for using powered chisels, which were both considerably lower than the Permissible Exposure Limit (PEL) by the Occupational Safety and Health Administration (OSHA) of 50 µg/m3. They were also below the Threshold Limit Value (TLV(R)) of 25 µg/m3 set by the American Conference of Governmental Industrial Hygienists (ACGIH(R)). If the outlier was included in the calculation, the corresponding 95% upper confidence limit for using wet grinders would become 30.1 µg/m3, which is still 40% lower than the OSHA PEL. Conclusions and Recommendations: The exposure levels recorded at this site indicated that the evaluated tools of wet grinders and a powered chisel with on-tool LEV were effective in reducing the worker's RCS exposures to concentrations below the OSHA PEL, and mostly below the ACGIH(R) TLV(R) as well. If workers use these types of tools and the associated engineering control measures for full-shifts, their 8-hour TWA exposures to RCS are expected to be at similar levels below the OSHA PEL as reported, provided that other conditions remain similar. The use of these types of tools and engineering control technology for tuckpointing is a preferred solution and adheres to the hierarchy of controls.
• Subjects:
  Construction Industry Dust Engineering Occupational Health Safety Silicon Dioxide Ventilation
• Keywords:
  Bricklayers Control Technology Crystalline Silica Dust Control Equipment Dust Suppression Engineering Control Engineering Controls Exhaust Ventilation Grinding Equipment Masons OSHA Region 3 Power Chisel Respirable Crystalline Silica Respirable Dust Tools Tuckpointing Water Sprays Wet Grinding

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• Series:
  Engineering and Physical Hazards Survey Reports
• DOI:
  https://doi.org/10.26616/NIOSHEPHB2022DFSE820
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Name as Subject:
  Packer Memorial Church
• Genre:
  Field Study
• Place as Subject:
  Pennsylvania ; Bethlehem (PA) ; OSHA Region 3
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DFSE - Division of Field Studies and Engineering ; EPHB - Engineering and Physical Hazards Branch
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-18
• Contributor:
  Feng, H. Amy
• NIOSHTIC Number:
  nn:20063863
• Citation:
  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. 2022-DFSE-820, 2021 Oct ; :1-18
• CAS Registry Number:
  Quartz (SiO2) (CAS RN 14808-60-7)
• Federal Fiscal Year:
  2022
• NORA Priority Area:
  Construction
• Peer Reviewed:
  False
• NAICS and SIC Codes:
  238140 - Masonry Contractors - (NAICS)
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:ed4137494de1f4b130e23ddd3ff8cb389823b056e24c0860ae530abe59c60b55da4abe3eb8c7e07ebf7e8e2da1ddeaf1d2ed8d7e7b6a8ebcdeb55fea90bd76e1
• Download URL:
  https://stacks.cdc.gov/view/cdc/174849/cdc_174849_DS1.pdf
• File Type:
  [PDF - 2.70 MB ]