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Evaluation of misting controls to reduce exposure to respirable crystalline silica for workers engaged in brick cutting.

Beamer-B; Watkins-D; Shulman-S; Maynard-A
American Industrial Hygiene Conference and Exposition, May 8-13, 2004, Atlanta, Georgia. Fairfax, VA: American Industrial Hygiene Association, 2004 May; :77
It is estimated that more than 1.7 million workers in the U.S. have been exposed to respirable crystalline silica, with a large percentage having been exposed to silica concentrations higher than limits set by current standards and regulations. The purpose of this study is to characterize the use of water-type engineering controls to reduce exposure to respirable crystalline silica for construction workers engaged in the task of brick cutting. Since data concerning the efficacy of engineering controls collected at work sites is often confounded by variations like wind, worker skill level, etc., experimentation was conducted in a laboratory environment. A completely enclosed testing chamber housed the brick-cutting saw. Respirable dust concentrations were measured by the Model 3321 Aerodynamic Particle Sizer Spectrometer. Specifically, the laboratory experiment was designed to compare dust suppression of water misting with conventional flooding techniques. Three flow rates of the brass atomizing nozzles were used for making this comparison: low (4.8 gallons per hour), medium (8.6 gallons per hour), and high (17.3 gallons per hour). The flow rate for flooding was 48 gallons per hour. The experiment consisted of five replications of five samples each (low-misting, medium-misting, high-misting, flooding, and no control). The order of sampling within each replicate was completely randomized. Results showed that low-misting nozzles reduce respirable dust levels by about 62%, mid-misting nozzles by about 71%, high-misting nozzles by about 82%, and flooding by about 92%. Based on these results, it may be feasible to use misting to control respirable silica dust instead of flooding. This strategy is of practical interest to the construction industry which must frequently limit the amount of water used on construction sites for a variety of reasons.
Silica-dusts; Occupational-exposure; Respirable-dust; Engineering-controls; Laboratory-testing; Environmental-factors; Dusts; Dust-particles; Sampling; Construction; Cutting-tools; Dust-suppression
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Research Tools and Approaches: Control Technology and Personal Protective Equipment
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American Industrial Hygiene Conference and Exposition, May 8-13, 2004, Atlanta, Georgia