In-depth survey report: partnering to control dust from fiber-cement siding, City Walk, Woodbury, Minnesota.
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 358-14a, 2014 Apr; :1-24
Background: 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 has been shown to cause excessive exposures to respirable crystalline silica. NIOSH scientists are conducting a study to develop engineering control recommendations for respirable crystalline silica from cutting fiber-cement siding. This site visit was part of that study. Assessment: NIOSH staff visited City Walk construction site in Woodbury, MN on July 23-25, 2013. During the site visit, they performed industrial hygiene sampling which measured the exposures to respirable dust and respirable crystalline silica of two workers who cut fiber-cement panel siding. Two different engineering control measures were implemented and tested separately. One had a dust-collecting circular saw connected to a regular shop vacuum. The shop vacuum provided local exhaust ventilation to remove the dust generated from cutting fiber-cement siding. The other control measure was a prototype circular saw with a built-in cyclone dust collector and an air filter. The NIOSH scientists also monitored the wind speed and direction at the site, and collected data about the work process in order to understand the conditions that led to the measured exposures. Results: Air sampling for respirable crystalline silica showed that on all three days, the 10-hour time weighted average (TWA) exposure to respirable crystalline silica for the cutter who used the shop vacuum control measure was in the range of 0.013 to 0.033 mg/m3. This was lower than the NIOSH Recommended Exposure Limit (REL) of 0.05 mg/m3 TWA, for up to a 10-hour workday in a 40-hour workweek. The 8-hour TWA exposure to respirable crystalline silica for this cutter was in the range of 0.016 to 0.041 mg/m3. On only one of the three days, it exceeded the Threshold Limit Value (TLV) of 0.025 mg/m3 TWA for an 8-hour workday and a 40-hour workweek. The TLV is a product of the American Conference of Governmental Industrial Hygienists (ACGIH). The cutter's respirable dust exposures were also considerably lower than the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for respirable dust that contains greater than 1% crystalline silica. His 8-hour TWA respirable dust exposures during the survey ranged from 0.09 to 0.29 mg/m3, with the corresponding PEL in the range of 1.12 to 1.32 mg/m3. For the cutter who used the prototype circular saw with a built-in cyclone dust collector and an air filter, the 10-hour TWA exposure to respirable crystalline silica was higher than the NIOSH REL on two of the three days; the 8-hour TWA exposure was also higher than the ACGIH TLV on two of the three days. For this cutter, the 8-hour TWA exposures to respirable dust that contains greater than 1% crystalline silica were in the range of 0.19 to 0.83 mg/m3, which was lower than the corresponding OSHA PELs (ranging from 1.37 to 1.67 mg/m3). Conclusions and Recommendations: The exposure levels recorded at this site indicated that the evaluated engineering control measure consisting of a regular shop vacuum connected to a dust-collecting circular saw was effective in reducing the worker's respirable crystalline silica exposures to concentrations below the NIOSH REL on all three days, and below the ACGIH TLV on two days. The use of the shop vacuum control also resulted in the exposures to respirable dust containing silica below the OSHA PEL on all three days. This engineering control measure has the potential to provide an effective, simple and low cost solution for workers cutting fiber-cement siding. The engineering control measure consisting of a circular saw with a built-in cyclone dust collector and air filter was not as effective and will need further improvement to maintain exposures consistently below the NIOSH REL and ACGIH TLV for respirable crystalline silica.
Region-5; Control-technology; Engineering-controls; Construction-materials; Construction-industry; Construction-workers; Dusts; Silica-dusts; Fibrous-dusts; Respirable-dust; Dust-control; Dust-control-equipment; Respiratory-protective-equipment; Respiratory-protection; Quartz-dust; Cements; Concretes; Cutting-tools; Sampling; Vacuum-equipment; Ventilation; Exhaust-ventilation; Control-equipment; Control-systems; Dust-collection; Work-practices; Air-samples; Air-sampling; Time-weighted-average-exposure; Exposure-levels; Exposure-limits; Cyclone-air-samplers; Permissible-limits;
Author Keywords: Respirable dust; Respirable crystalline silica; Fiber-cement siding; Engineering control