A section of road was constructed in Northeastern Indiana in the summer of 1996 using waste foundry sand as the embankment construction material. Initial testing on the waste sand had determined no detrimental health effects. However, it was observed during construction that once the sand had dried, tire-road interaction raised copious clouds of black dust. This led to worker concern regarding airborne silica and silicosis. This study aimed at determining whether the threat of overexposure to airborne crystalline silica existed in regard to Occupation Health and Safety Administration’s (OSHA) Permissible Exposure Limit (PEL). Experiments carried out at the Auburn Foundry waste sand monofill in the summer of 1998 in which clouds of dust were purposefully generated and sampled by both respirable personal samplers and high volume area samplers showed that respirable crystalline silica dust did not overexpose the workers relative to the OSHA PEL. The negative findings of crystalline silica in the respirable samples were confirmed in the area samples by an second, independent laboratory. Calculations show that up to an average of 20% by weight of respirable size dust such as baghouse hopper dust can be allowed in the waste foundry sand. Specifying this amount of fine dust for waste foundry sand will provide a worker exposure safety factor of about 2.0 for protection against overexposure to crystalline silica dust. Removing the baghouse hopper dust material from the waste sand would reduce dust generation considerably. Recommended methods of dust abatement include watering down the dust during transportation, dumping, and compacting and keeping the sand wet during construction.

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waste foundry sand, crystalline silica, silicosis, dust generation, tridymite, cristobalite, SPR-2194

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

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