Silica Dust Control for Village-Scale Stone Crushing: A Computed Exposure Assessment and Priced Control Design

Computed exposure assessment and priced control design for respirable crystalline silica at a village-scale granite crushing plant (10 tonnes per hour). SIMULATED, NOT MEASURED; nothing was built or field-tested. Dry crushing gives a computed 8-hour time-weighted average exposure of 821 micrograms per cubic metre, 16.4 times the OSHA permissible exposure limit of 50. A control set of water suppression (six nozzles, 36.0 litres per tonne), partial enclosure, and operator repositioning reduces the computed average to 42.9 micrograms per cubic metre for a capital cost of $591, but it fails the ACGIH limit of 25 and fails the OSHA limit for higher-quartz rock, in calm air, with the water system off, or with more near-crusher time; respirators are therefore a required remaining layer, with an effective protection factor of 5.26 at 90 percent wear time for a half-mask assigned a factor of 10.