Comprehensive Report: Laboratory evaluation of power shears for cutting fiber-cement siding

Details

• Personal Author:
  Echt, Alan S. ; Qi, Chaolong
• Corporate Authors:
  National Institute for Occupational Safety and Health. Division of Applied Research and Technology
• Description:
  Workplace exposure to respirable crystalline silica 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 construction materials, such as brick, block, mortar, and concrete. Construction tasks that cut, break, grind, abrade, or drill those materials have been associated with overexposure to dust containing respirable crystalline silica. Fiber-cement products can contain as much as 50% crystalline silica and cutting this material with power saws has been shown to cause excessive exposures to respirable crystalline silica. NIOSH scientists conducted this study to evaluate power shears for cutting fiber-cement siding. Detailed characterizations of the dust generated from cutting fiber-cement siding using either power shears or a dust-collecting circular saw (C-M saw) were conducted in a laboratory setting. The C-M saw was tested with and without local exhaust ventilation (LEV), and the results of those tests were compared. For all the test conditions (the power shears and the C-M saw with and without LEV), particle size data obtained with the Aerodynamic Particle Spectrometer (APS), a real-time direct-reading instrument, showed a lognormal number-based size distribution with geometric mean diameters ranging from 0.9-1.1 um and geometric standard deviations ranging from 1.5-1.8. The C-M saw without LEV generated the largest amount of dust with an average total number concentration of 5,695 particles/cm3, estimated from fitting the data to a lognormal distribution. The test of the C-M saw with LEV (with an exhaust air flow rate of 2.54 m3/min or approximately 90 CFM) resulted in an estimated total number concentration of 564 particles/cm3, which corresponds to a approximately 90% reduction compared to using the saw without LEV. The power shears generated the least amount of dust, with an estimated total number concentration of only 34 particles/cm3, which is 94% lower than the C-M saw with LEV and 99.4% lower than the C-M saw without LEV. The mass-based size distributions showed a similar trend overall, with the power shears generating considerably less dust, even when the results were compared to the C-M saw with LEV. The laboratory testing system provides reliable characterization of the respirable dust generation rate, GAPS (expressed as grams of dust per meter of board cut, g/m), from cutting fiber-cement siding with different tools. The GAPS derived from the APS data for the power shears was significantly lower than that for the C-M saw with LEV (a mean of 0.0059 g/m versus 0.0289 g/m, P<0.001), which in turn, was significantly lower than that for the C-M saw without LEV (a mean of 0.0289 g/m versus 0.4003 g/m, P<0.001). The results from the laboratory tests suggest that the reduction of GAPS from using LEV with dust-collecting circular saws is largely in agreement with the previously reported exposure reductions obtained from field surveys of construction sites where this control measure was used. The significantly lower GAPS for the power shears compared to that of the C-M saw with or without LEV indicates that cutting fiber-cement siding using similar power shears could be expected to result in an 8-hr TWA exposure to respirable crystalline silica lower than those observed in the field surveys using dust collection circular saws with LEV (0.013+/-0.009 mg/m3) and without LEV (0.084+/-0.055 mg/m3). From the perspective of exposure control, the use of power shears whenever practical is a preferred method for cutting fiber-cement siding, and its use adheres to the hierarchy of controls.
• Subjects:
  Construction Industry Dust Engineering Environmental Monitoring Laboratories Occupational Health Particulate Matter Quartz Safety Silicon Dioxide Ventilation

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• Keywords:
  Cements Concretes Construction-equipment Control-technology Crystalline Silica Cutting Tools Dust-collection Dust Measurement Dust Particles Engineering-controls Engineering Control Equipment Testing Exhaust Ventilation Exposure-assessment Exposure-levels Exposure-limits Fiber-cement Siding Laboratory Testing OSHA Region 5 Particle Aerodynamics Particle Diameter Particle Size Power Tools Quartz-dust Respirable-dust Respirable Crystalline Silica Respirable Dust Silica-dusts Tools

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• Series:
  Engineering and Physical Hazards Survey Reports
• DOI:
  https://doi.org/10.26616/NIOSHEPHB35821a
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Genre:
  Field Study
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DART - Division of Applied Research and Technology ; EPHB - Engineering and Physical Hazards Branch
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-21
• NIOSHTIC Number:
  nn:20049950
• 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 358-21a, 2017 May ; :1-20
• CAS Registry Number:
  Quartz (SiO2) (CAS RN 14808-60-7)
• Federal Fiscal Year:
  2017
• NORA Priority Area:
  Construction
• Peer Reviewed:
  False
• NAICS and SIC Codes:
  238170 - Siding Contractors - (NAICS)
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:5522f97e840a55ee51dbe2105b5ed6897c41300ca81d78667e714862cd5bbef98f1321c1b56ef17b67220084f6279cd79afcf5ea320a37cc19c57f7e7b0ff2ab
• Download URL:
  https://stacks.cdc.gov/view/cdc/175016/cdc_175016_DS1.pdf
• File Type:
  [PDF - 576.36 KB ]