Abstract:
This 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. Work activities were performed by union-sponsored apprentices and included tuck point grinding a brick wall (angular grinder), surface grinding a concrete wall (surface grinder), paver block and brick cutting (masonry saw) and concrete block cutting (hand-held saw). In a randomized block design, implemented under controlled field conditions, three ventilation rates (0, 30, and 75 CFM) were tested for each tool/LEV system. With the exception of the hand-held saw, the use of LEV resulted in a significant (p<0.05) reduction in respirable dust exposure. The mean exposure levels for the 75 CFM treatments were less than that of the 30 CFM treatments; however, differences between these treatments were only significant for tuck point grinding (p<0.1) and paver block cutting (p<0.01). Although exposure reduction was significant (70-90% at the low ventilation rate and 80-95% reduction at the high ventilation rate), personal respirable quartz exposures remained very high (1.5-2.5 x PEL at the low ventilation rate and 0.5 to 1.5 x PEL at the high ventilation rate). 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, may allow effective use of administrative controls, reduces exposure to nearby workers and reduces clean-up associated with dust exposures.