Projects - Silica Dust
Silica Exposure During Granite Countertop Fabrication
Workers engaged in fabricating granite kitchen tops, kitchen islands, tables, tiles, lathed banisters, and other customized stone pieces were evaluated for their exposure to silica. Tasks generating visible and significant airborne granite dust included cutting, grinding, and finishing. Granite countertop fabricators were found to be at risk for silicosis. Wet processes significantly reduced worker exposure to respirable crystalline silica to below Washington State’s permissible exposure level. Wet processes were adopted by the small companies in this case study because they found several cost effective tools that were easy to use and applicable to stone fabrication work. Since the NIOSH recommended exposure limit for respirable crystalline silica was exceeded at most of the worksites using wet processes in this study, employers were urged to continue exploring ways to reduce silica exposures to as low a level as possible.
Simcox NJ, Lofgren D, Leons J, Camp J. Silica exposure during granite countertop fabrication. Appl Occup Environ Hyg. 1999 Sep;14(9):577-82.
Engineering Controls for Silica Dust
This NIOSH-funded study assessed the effectiveness of commercially available local exhaust ventilation (LEV) systems for controlling respirable dust and crystalline silica exposures during concrete cutting and grinding activities. In a randomized block design, implemented under controlled field conditions, three ventilation rates (0, 30 and 75 CFM) were tested for each tool and LEV system used by workers engaged in tuck point grinding a brick wall, surface grinding a concrete wall, cutting paver block and brick, and cutting concrete block. With the exception of the hand-held saw, the use of LEV resulted in a significant reduction in respirable dust exposure, although exposures remained 0.5 to 2.5 times the permissible exposure level. Nonetheless, this dust control alternative reduces the risk of workers developing disease, allows workers to use a lower level of respiratory protection, protects workers during short duration work episodes, reduces exposure to nearby workers, and reduces cleanup-associated dust exposures.
G. Croteau, S. Guffey, M. Flanagan, and N. Seixas. The Effect of Local Exhaust Ventilation Controls on Dust Exposures During Masonry Activities. AIHA Journal 63:458–467 (2002)
Wet Concrete Sawing and Drilling
This study was an effort to characterize workplace exposures to silica and respirable dust in order to develop new or enhance existing respiratory protection policies. The study was conducted at ten different construction sites. Four tools were evaluated: walk-behind and hand-held slab saws, core drill, and wall saw. The 8-hour exposures for the 13 samples were found to be at or above the permissible exposure level in five cases. Water appeared to be effective in reducing emissions during concrete cutting and drilling. However, the potential for overexposures to silica when working in an enclosed environment still existed, both for the tool operator and adjacent workers. Therefore, when cutting concrete inside using water for dust suppression, this study recommended that saw operators and others in the area wear respiratory protection.
Flanagan ME, Loewenherz C, Kuhn G. Indoor wet concrete cutting and coring exposure evaluation. Appl Occup Environ Hyg. 2001 Dec;16(12):1097-100.
FRCG Quarry Sampling Summary Report
The FIELD GROUP developed a summary report of sampling results for noise and silica at 10 open surface mines. Samples were collected across all seasons for a year. Employees who had a potential for exposure to noise or silica dust were monitored. For all eight jobs monitored, the mean 8-hour noise exposure exceeded 85 dBA. The exposure of only groundsmen exceeded 90 dBA, although crusher mechanics had exposures approaching this limit. For silica exposure, only groundsmen had a mean exposure at the silica permissible exposure level of 10 mg/m3. Recommended controls included fitting heavy equipment with cabs and air conditioning, fitting generators with supply and exhaust air mufflers, upgrading conveyor belts to reduce the need for belt cleaning by a groundsman, soundproofing the crusher operator’s booth, and shifting groundsmen's work schedules to reduce their time near operating equipment.
Silica Dust Exposures During Selected Construction Activities
Eight common construction tasks were evaluated for quartz and respirable dust exposure. The geometric mean quartz concentration was 0.10 mg/m3, with 71% exceeding the threshold limit value. Activities with the highest exposures were surface grinding, tuck-point grinding, and concrete demolition. Factors important to exposure included tool used, work area configuration, controls employed, cross draft, and in some cases nearby dust. Respiratory protection was found to be inadequate for 42% of exposures. Exposures were reduced by using a box fan for surface grinding and floor sanding, and a vacuum/shroud for surface grinding, with reductions of 57, 50, and 71%, respectively. The study concluded that the usual protection method, respirators, was not always adequate, and the use of engineering controls was infrequent and often ineffective.
Flanagan M.E., N. Seixas, M. Majar, J. Camp, M. Morgan. Silica Dust Exposures During Selected Construction Activities. AIHA Journal 64:319–328 (2003).
The Efficacy of Local Exhaust Ventilation for Controlling Dust Exposures During Concrete Surface Grinding
This study assessed the effectiveness of a commercially available local exhaust ventilation (LEV) system for controlling respirable dust and crystalline silica exposures during concrete grinding activities. Three different dust collection shroud configurations were tested during surface grinding by cement masons at six commercial construction sites. Data obtained with a direct reading respirable dust monitor were adjusted to remove non-work task-associated dust exposures and were subsequently used to calculate the exposure reduction achieved. The application of LEV resulted in a reduction in the overall geometric mean respirable dust exposure from 4.5 to 0.14 mg/m3, a mean exposure reduction of 92%. Despite the effective control of dust generated during surface grinding, 22% of the samples collected while LEV was being used were greater than the 8 hour time-weighted average permissible exposure limit, and 26% greater than the threshold limit value for respirable crystalline silica.
Croteau G., M. E. Flanagan, J. Camp and N. Seixas..The Efficacy of Local Exhaust Ventilation for Controlling Dust Exposures During Concrete Surface Grinding. Annals of Occupational Hygiene 2004 48(6):509-518.
Silica Exposures in Construction: What Workers Need to Know
This brochure describing silica exposure is targeted towards construction. It recommendeds the use of respirators for eight common construction tasks.
Development of an ACGIH Construction Industry Silica Exposure Database Overview
A silica monitoring data compilation project was initiated through the American Conference of Governmental Industrial Hygienists Construction Committee. Personal silica exposure monitoring data was collected and analyzed from 13 private, research and regulatory groups. An effort was made to collect as much information as possible about task, tool, environmental and control conditions. Results from 1,374 personal quartz samples reported had a geometric mean (GM) of 0.13 mg/m3 and a GSD of 5.9. Highest exposures were reported for abrasive blasters, surface and tuckpoint grinders, jackhammers, and rock drills. Results were considerably higher for short term samples (up to 2 hours) than for mid term (2-6 hours) or longer (over 6 hour) samples. For nearly all exposure variables, a large portion of variable categories were at or over the quartz occupational exposure limit of 0.05 mg/m3. The data variability within task and tool was very large, with some very high exposures reported for a broad spectrum of tools. These results indicate that respiratory protection commonly used on construction sites is often inadequate for the exposures encountered. Further understanding of the conditions leading to high exposures will require more detailed documentation of the sample characteristics following database design recommendations or systematic surveys of exposure in this complex industry.
Silica Exposure on Construction Sites: Results of an Exposure Monitoring Data Compilation Project
To expand on the limited size and scope of construction silica exposure studies, a silica monitoring data compilation project was initiated through the American Conference of Governmental Industrial Hygienists Construction Committee. Personal silica exposure monitoring data was collected and analyzed from 13 private, research, and regulatory groups. An effort was made to collect as much detail as possible about task, tool, and environmental and control conditions so as much information as possible could be garnered. There were considerable data gaps, particularly with regulatory agency data, that represented over half of the data set. There were 1374 personal quartz samples reported with a geometric mean of 0.13 mg/m(3) and a GSD of 5.9. Descriptive statistics are reported by trade, task, tool, and data source type. Highest exposures were for abrasive blasters, surface and tuckpoint grinders, jackhammers, and rock drills. The sample period was important, with short-term samples (up to 2 hours) having considerably higher levels than midterm (2-6 hours) or longer (over 6 hours) samples. For nearly all exposure variables, a large portion of variable categories were at or over the quartz occupational exposure limit of 0.05 mg/m(3), including 8 of 8 trade, 13 of 16 task, and 12 of 16 tool categories. The respiratory protection commonly used on construction sites is often inadequate for the exposures encountered. The data variability within task and tool was very large, with some very high exposures reported for a broad spectrum of tools. Further understanding of the conditions leading to high exposures will require more detailed documentation of the sample characteristics following database design recommendations or systematic surveys of exposure in this complex industry.
Flanagan M.E., N. Seixas, P. Becker, B. Takacs, and J. Camp. Silica Exposure on Construction Sites: Results of an Exposure Monitoring Data Compilation Project. Journal of Occupational and Environmental Hygiene 2006 Mar;3(3):144-52.
Addition all information : UW Silica Dust On Construction Sites website