Evaluation of cut-off saw exposure control methods for respirable dust and crystalline silica in roadway construction.
Middaugh-B; Hubbard-B; Zimmerman-N; McGlothlin-J
J Occup Environ Hyg 2012 Mar; 9(3):157-165
Dust reduction equipment adapted for single-person operation was evaluated for gas-powered, commercially available cut-off saws during concrete curb cutting. Cutting was performed without dust control and with two individual exposure control methods: wet suppression and local exhaust ventilation (LEV). The wet suppression system comprised a two-nozzle spray system and a 13.3-L hand-pressurized water supply system with an optimum mean flow rate of 0.83 L/min for 16 min of cutting. The LEV system consisted of a spring-loaded guard, an 18.9-L collection bag, and a centrifugal fan with an estimated exhaust rate of 91 ft3/min. Task-based, personal filter samples were obtained for four saw operators during cutting durations of 4 to 16 min on five job sites. Seventeen filter samples were collected without dust control, 14 with wet suppression, and 12 with LEV, yielding a geometric mean respirable dust concentration of 16.4 mg/m3, 3.60 mg/m3, and 4.40 mg/m3, respectively. A dust reduction of 78.0% for wet suppression and 73.2% for LEV was observed vs. no dust control. A statistically significant difference (p < 0.001) was also revealed for wet suppression and LEV when compared with no dust control; however, a significant difference (p=0.09) was not observed between wet suppression and LEV. Despite these significant dust reductions, workers are still projected to exceed the ACGIH 8-hr timeweighted average threshold limit value for quartz (0.025 mg/m3) in less than 1 hr of cutting for both dust control methods. Further research is still needed to improve dust reduction and portability of both control methods, but the current LEV system offers important advantages, including a drier, less slippery work area and year-round functionality in cold weather.
Construction; Construction-equipment; Construction-industry; Construction-materials; Road-construction; Respirable-dust; Quartz-dust; Silica-dusts; Power-tools; Cutting-tools; Dust-control; Dust-suppression; Dust-control-equipment; Particulate-dust; Concretes; Control-equipment; Equipment-design; Employee-exposure;
Author Keywords: concrete; construction; control; exposure; quartz; respirable; saw; silica
Beauregard Middaugh, Purdue University, School of Health Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47907
Journal of Occupational and Environmental Hygiene
University of Cincinnati