In-Depth Survey Report: Field Evaluation of a Mobile Dust Control Booth for Stone Countertop Grinding

Details

• Personal Author:
  Echt, Alan S. ; 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. Stone countertop products can contain >90% crystalline silica and working with this material during stone countertop fabrication and installation has been shown to cause excessive RCS exposures. NIOSH scientists are conducting a study to develop engineering control recommendations for RCS in the stone countertop fabrication and installation tasks. This site visit is part of that study. Assessment: NIOSH scientists visited the company Stone Systems of Houston, Texas on June 28-30, 2016. During the site visit, NIOSH scientists evaluated the effectiveness of a mobile dust control booth installed at the site. During the survey, researchers collected breathing zone air samples to assess the short-term respirable dust and RCS exposures of a worker who performed wet grinding inside the mobile dust control booth both with and without the booth's filtration unit running. Additionally, a handheld pneumatic wet grinder was used that featured a center-water-feed for suppressing dust at its source. NIOSH scientists recorded detailed survey notes about the work process to understand conditions leading to measured dust and RCS exposures. Results: Respirable dust concentration monitored from an aerosol photometer was significantly higher when the exhaust air from the pneumatic grinder was in the opposite direction of the airflow in the booth (P<0.01). This result suggests that the orientation of the grinder's exhaust deflector can affect the exposure level when it is used in a dust control booth. Thus, subsequent tests were conducted with the deflector set to allow the exhaust air to flow along the same direction as the general booth airflow. Additionally, when the booth's filtration unit was running at an average airflow velocity of 133.6 +/- 8.1 fpm, the worker's exposure was significantly reduced compared to values when the filtration unit wasn't running. The reduction of exposure on respirable dust from the aerosol photometer (75.9%) and air samples (73.5%) as well as that on RCS are in reasonable agreement (78.7%). Conclusions and Recommendations: When grinding stone countertops in a dust control booth, it is a best practice to adjust the grinder's exhaust deflector to allow the exhaust air to flow in the same direction as the airflow in the booth. The aggregated results of the short-term task-based time weighted average exposure to RCS from previous field surveys have a mean of 237.5 and 69.3 ug/m3 for grinders and polishers, respectively, when working exclusively with engineered quartz stone. Therefore, it is likely that the dust control booth running at the evaluated airflow velocity would reduce RCS exposure below the NIOSH Recommended Exposure Limit (REL) of 0.05 mg/m3 for polishers, but not for grinders. Additional engineering control measures are thus needed for the grinding process to consistently reduce exposures below the NIOSH REL. In the absence of sufficient dust controls, respirators should continue to be used to reduce exposures, and the employer needs to ensure that their respiratory protection program follows OSHA standards.
• Subjects:
  Air Movements Dust Engineering Environmental Exposure Environmental Monitoring Filtration Manufacturing And Industrial Facilities Occupational Exposure Occupational Health Personal Protective Equipment Quartz Respiratory Protective Devices Safety Silicon Dioxide Ventilation Workplace

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• Keywords:
  Air Flow Air Samples Air Sampling Breathing Zone Control Technology Crystalline Silica Dust Control Dust Control Booth Dust Control Equipment Dust Exposure Dust Inhalation Dust Measurement Dust Sampling Dust Suppression Employee Exposure Engineering Control Engineering Controls Equipment Testing Exhaust Ventilation Exposure Assessment Exposure Levels Exposure Limits Grinding Equipment Manufacturing OSHA Region 6 PELs Permissible Exposure Limits Personal Protective Equipment Pneumatic Equipment PPE Quartz Dust Recommendations Recommended Exposure Limits RELs Respirable Crystalline Silica Respirable Dust Respirators Respiratory Protection Sampling Short Term Exposure Silica Dusts Stone Countertop Stone Grinders Stone Products Task Performance Water Sprays Workplace Studies

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• Series:
  Engineering and Physical Hazards Survey Reports
• DOI:
  https://doi.org/10.26616/NIOSHEPHB2020DFSE165
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Name as Subject:
  Stone Systems of Houston
• Genre:
  Field Study
• Place as Subject:
  Texas ; OSHA Region 6
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DART - Division of Applied Research and Technology ; DFSE - Division of Field Studies and Engineering ; EPHB - Engineering and Physical Hazards Branch
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-17
• NIOSHTIC Number:
  nn:20058064
• NTIS Accession Number:
  PB2020-100149
• 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. 2020-DFSE-165, 2019 Nov ; :1-17
• CAS Registry Number:
  Quartz (SiO2) (CAS RN 14808-60-7)
• Federal Fiscal Year:
  2020
• NORA Priority Area:
  Construction ; Manufacturing
• Peer Reviewed:
  False
• NAICS and SIC Codes:
  327991 - Cut Stone and Stone Product Manufacturing - (NAICS)
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:aa7a324a983db386ab017c201afc0a6453747e5752e283be38c37a101bcada059bf263588f1194e71b312787874ffcfe8c3fae8f9b2935ffd4741116e9eb9575
• Download URL:
  https://stacks.cdc.gov/view/cdc/174846/cdc_174846_DS1.pdf
• File Type:
  [PDF - 1.86 MB ]