In-Depth Report: Control Technology for Crystalline Silica Exposures inConstruction: Exposures and Preliminary Control Evaluation at Various Sites for Bricklayers Local No. 9, Pittsburgh, Pennsylvania

摘要

Respirable silica exposures were measured while workers were using grinders toremove old mortar during a building renovation. Respirable silica exposures ranged from 1.0 to 3.0 mg/cu m grinding mortar, well in excess of the NIOSH Recommended Exposure Limit of 50 micrograms/cu m. A preliminary evaluation of available engineering controls revealed that control measures ineffectively control the dust generation by the grinding operation. Control measures evaluated included two ventilated shrouds for grinding and the application of water to the grinding wheel. Testing on one ventilated shroud was terminated because dusty air, which was likely to contain an excessive amount of respirable crystalline silica, was emitted from the back of the grinder. A 30-minute exposure measurement resulted in a measured exposure of 9 mg/cu m of respirable crystalline silica. A commercially available grinder was tested which also emitted much dust. A wet grinding device resulted in a respirable dust concentration of 0.3 mg/cu m for a one hour sampling period. Apparently, wet grinding can suppress dust emission. However, the use of water with an electric grinder raises concerns about electrical shock hazards for the operator.