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In-Depth Survey Report: Comparison of Removing Mortar by Powered Chisels, Manual Chisels and Angle Grinders
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2022/08/01
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By Qi, Chaolong
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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 Detroit Women's City Club in Detroit, Michigan, between August 13 to 16, 2019, and performed industrial hygiene sampling, which measured short-term task-based exposures to respirable dust and RCS while five workers used power chisels, manual chisels, and dry grinders with on-tool local exhaust ventilation (LEV) to remove mortar from brick walls. The NIOSH researcher also observed the work process to understand the conditions that contributed to the measured exposure. Results: Only one of the three air samples from using power chisels had a detectable amount of RCS, and its time weighted average (TWA) RCS exposure was 41.7 microg/m3. Excluding the sample with both respirable dust and RCS masses below their detection limits, the three samples associated with using manual chisels had TWA RCS exposures ranging from 19.5 to 34.1 microg/m3 with a mean of 27.3 microg/m3 and a standard deviation of 7.3 microg/m3. The eight samples associated with using both manual chisels and dry grinders had TWA RCS exposures ranging from 62.1 to 470.6 microg/m3 with a mean of 182.5 microg/m3 and a standard deviation of 163.6 microg/m3. The short-term TWA exposures from using manual chisels were significantly lower than those from using both manual chisels and dry grinders (P = 0.014 for respirable dust and P = 0.016 for RCS). Conclusions and Recommendations: The exposure levels recorded at this site indicated that the manual chisels used in this survey effectively controlled the dust emissions and reduced the workers' RCS exposures. Although the result of the air sample from using power chisel was encouraging, the result is not conclusive because of the very limited sample size. Additional field studies evaluating power chisels with or without the use of LEV over a full-shift will be needed to establish its effectiveness in controlling workers RCS exposure during tuckpointing. The overall results from this survey indicate that using power chisel is likely to lead to lower RCS exposure compared to using dry grinders with LEV. When applicable, the use of tools such as manual and power chisels and engineering control technology such as LEV for tuckpointing is a preferred solution and adheres to the hierarchy of controls. Before sufficient dust controls are validated and implemented, respirators should continue to be used to reduce exposures, and the employer needs to make sure that the respiratory protection program follows the OSHA standard.
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Pages in Document:1-18
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NIOSHTIC Number:nn:20065940
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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-1109, 2022 Aug;:1-18;
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Federal Fiscal Year:2022
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Peer Reviewed:False
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[PDF-1.17 MB]