Effectiveness of Dust Control Methods for Crystalline Silica and Respirable Suspended Particulate Matter Exposure During Manual Concrete Surface Grinding

Concrete grinding exposes workers to unacceptable levels of crystalline silica dust known to cause diseases such as silicosis and possibly lung cancer This study examined the influence of major factors of exposure and effectiveness Of existing dust control methods by simulating field concrete grinding in an enclosed workplace laboratory Air was monitored during 201 concrete grinding sessions while using a variety of grinders accessories and existing dust control methods, including general ventilation (GV) local exhaust ventilation (LEV), and wet grinding Task specific geometric mean (GM) of respirable crystalline silica dust concentrations (mg/m(3))for LEV HEPA LEV Shop-vec wet- and uncontrolled grinding while GV tins Won were 0 17/009 057/0 13 1 11/0 44 and 23 1/6 80, respectively Silica dust concentrations (mg/m3) using 100-125 mm (4-5 inch) and 180 mm (7 inch) grinding cups were 0 53/0 22 and 2 43/0 56 respectively GM concentrations of silica dust were significantly lower for (1) GV on (66 0%) vs off and (2) LEV HEPA- (99 0%) LEV Shop vac (98 1%) or net (94 4%) vs uncontrolled grinding Task-specific GM of respirable suspended particulate matter (RSP) concentrations (mg/m3)for LEV HEPA- LEV Shop vac wet and uncontrolled grinding, while GV was off/on, were 1 58/0 63, 7 20/1 15 9 52/4 13, and 152/478, respectively GM concentrations of RSP using 100-125 nun and 180 nun grinding cups were 4 78/1 62 and 22 2/5 06, respectively GM concentrations of RSP were significantly loiter for ( 1) GV on (70 2%) vs off and (2) LEV HEPA (98 9%) LEV Shop vac (96 9%) or wet (92 6%) vs uncontrolled grinding Silica dust and RSP were not significantly affected by (1) orientation of grinding surfaces (vertical vs inclined) (2) water flow rates for net grinding (3) length of task-specific sampling time, or (4) among cup sizes of 100 115 or 125 mm No combination of factors or control methods reduced an 8 hr exposure level to below the recommended criterion of 0 025 mg/m3 jiff crystalline silica requiring further refinement in engineering controls administrative controls or the use of respirators