CRUSHED STONE INDUSTRIES AND RESPIRABLE DUST IN SOUTHERN INDIA

Increasing development in southern India is driving demand for high quality crushed stone for stable roadbeds. This demand is being met by hundreds of independent quarrying and crushing operators. Preliminary data and site visits suggest two classes of geologic health risks. One is for the workers in the quarries and crushing plants. A second is to the general population from wind-borne dust during dry and windy times of the year. Although some recognize the health risks, economic factors favor continued production. Because of the continuing challenge the documentation of the risks and exploration of low cost mitigations to these respiratory health risks are in demand. Several quarries and crushing plants were surveyed in the Vellore district. Some dust is generated in quarries during drilling and blasting but the majority is generated in nearby crushing plants. Jaw crushers reduce boulders and roller screens grade the crushed material into four gravel size fractions plus residual sand and dust. About one fourth of the starting material is lost as fines. Samples filtered from the air around the crushing plants match the composition of the rock and consist of about 60% feldspar, 30% quartz, 5% biotite, and 5% pyroxene based on thin section and XRD. SEM-EDS analysis shows the compositions persist to respirable dust size fractions. Positions of crushing plants are being incorporated into a GIS database and collection of airborne dust from surrounding communities and modeling of dust transport is planned. Recommended dust mitigation methods include: use of masks, water misting at the roller mills from water that collects in the quarries, and orienting crusher plants so that workers are upwind of the dust cloud. Local community health officials and quarry owner associations are communicating, but implementation of safety improvements will depend on motivation. Stimulating factors include clear demonstrations of health risks to local officials and development of a use for the fine fraction of crushed material that will favor its capture.