In-Depth Survey Report: Concrete Surface Preparation Tools Machines 7

Details

• Personal Author:
  Echt, Alan S. ; Garcia, Alberto ; Marlow, David A.
• 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. Colored, stained, and polished concrete floors are increasingly popular for use in homes, offices, retail establishments, schools, and other commercial and industrial settings. Some businesses specify integrally-colored concrete floors in new stores in place of vinyl composite tile. Polished concrete floors are durable, sanitary, and easy to maintain. NIOSH scientists are conducting a study to develop and evaluate engineering control recommendations for respirable crystalline silica from concrete polishing operations. This survey was part of that study. NIOSH staff visited the Operative Plasterers' and Cement Masons' International Association (OPCMIA) facility in New Brighton, MN on two different trips in March and May, 2015. During these site visits, personal breathing zone (PBZ) air samples were collected to measure the respirable dust and respirable crystalline silica exposures of the operator while he used a concrete polisher (Prep-Master 2420, Substrate Technology, Inc., Morris, IL). Additionally, area samples were collected on top of the machine during the completion of the task. The Prep-Master 2420 floor polisher was outfitted with a local exhaust ventilation system consisting of two exhaust ports located on the back of the shroud that encased twelve polishing tools. The exhaust from both ports was connected to a vacuum system rated at approximately 7929 liters per minute (L/min) (280 cubic feet per minute (cfm)) of suction. The vacuum was equipped with a pre-separator. Once through the pre-separator, the air stream passed through a double High Efficiency Particulate Air (HEPA) filter and then recirculated to the room. The aim of this survey was to collect emissions data from the concrete polisher using different grits while operating the dust collection system provided with the machine. Sample times varied based on the length of time needed to polish a rectangular area of 20 square-meters (m2) (216 square-feet (ft2)) with a given grit and ranged between 28 to 34 minutes with an average sample time of 31 minutes. Overall, the air samples measured from 16 to 51% quartz. The mean quartz percentage for all of the air samples was 28%. A bulk sample was collected from the dust captured in the bag filter of the vacuum system connected to the concrete polisher
  
  it contained 27% quartz. No cristobalite or tridymite were detected in the bulk sample. Therefore, for the purposes of this report the terms respirable crystalline silica or respirable quartz may be used interchangeably. If exposures were to continue throughout the entire work-day and assuming steady, constant, and similar dust generation rates as the ones observed during this survey, the LEV used with the Prep-Master 2420 concrete polisher would not be able to adequately protect workers from exposures above the NIOSH REL or the OSHA PEL of 0.05 mg/m3. With these assumptions in mind, on average, the collected samples with different polishing grits were below the NIOSH REL (about 0.7 times the REL) but ranged from 0 to 2.5 times greater than the NIOSH REL. Of the 60 collected samples, 17 samples matched or exceeded the NIOSH REL. The metal bond grit generated respirable crystalline silica (quartz) concentrations of 124 ug/m3 which is over two times higher than the NIOSH REL. The resin bond grits generated crystalline silica exposures of 121 ug/m3 which is also over two times the NIOSH REL. The Prep-Master 2420 concrete polisher evaluated in this survey was equipped with a local exhaust ventilation (LEV) system intended to control and remove dust particles generated during the concrete polishing process. However, the dust control system needs modifications so that worker exposure to respirable crystalline silica can be reduced during concrete finishing operations.
  
  
• Subjects:
  Construction Industry Dust Engineering Environmental Exposure Environmental Monitoring Manufacturing And Industrial Facilities Occupational Health Particulate Matter Quartz Safety Silicon Dioxide Ventilation Workplace

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• Keywords:
  Air Sampling Breathing Zone Concrete Polishing Concretes Construction Construction Workers Control Technology Crystalline Silica Dust Collection Dust Collectors Dust Control Equipment Dust Exposure Dust Particles Engineering Controls Equipment Testing Exhaust Ventilation Exposure Assessment Exposure Levels Exposure Limits Floors HEPA Filters High-efficiency Particulate Air Filters Local Exhaust Ventilation Machine Operators Machine Tools OSHA Region 5 Performance Tests Power Tools Quartz Dust Recommendations Recommended Exposure Limits RELs Respirable Dust Sampling Silica Silica Dusts Vacuum Cleaning Systems Work Environment Work Operations

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• Series:
  Engineering and Physical Hazards Survey Reports
• DOI:
  https://doi.org/10.26616/NIOSHEPHB36816a
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Name as Subject:
  Operative Plasterers’ and Cement Masons’ International Association
• Genre:
  Field Study
• Place as Subject:
  Minnesota ; New Brighton (MN) ; OSHA Region 5
• 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:
  1-28
• NIOSHTIC Number:
  nn:20057374
• NTIS Accession Number:
  PB2021-100212
• 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 368-16a, 2019 Oct ; :1-28
• CAS Registry Number:
  Quartz (SiO2) (CAS RN 14808-60-7)
• Federal Fiscal Year:
  2020
• NORA Priority Area:
  Construction
• Peer Reviewed:
  False
• NAICS and SIC Codes:
  238340 - Tile and Terrazzo Contractors - (NAICS) ; 238110 - Poured Concrete Foundation and Structure Contractors - (NAICS)
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:760e39aa93d14725cf32c21724bc37db636d2f8674e9406c831a32fce5aa3c7832005876622b60efc0a3f3d4b8108e2b5ec452439c9ba08a1c6d87f32779265c
• Download URL:
  https://stacks.cdc.gov/view/cdc/175027/cdc_175027_DS1.pdf
• File Type:
  [PDF - 1.27 MB ]