This report describes a study of atmospheric emissions from the crushed limestone industry. Crushed limestone plants emit particulates from drilling, blasting, transport on unpaved roads, crushing, screening, conveying, and stockpiling. The emission factor for total particulate from a representative plant producing 450 metric tons/hr of product is 3.5 g/metric ton. Vehicular movement on unpaved roads contributes 66% of the overall emissions and approximately 38% of the respirable particulate emissions. The hazardous constituent in the dust is free silica (1.2% by weight). Nitrogen oxides and carbon monoxide are emitted by the blasting operation, but their emission factors are small in comparison to that of particulate emissions. In order to evaluate the potential environmental effect of crushed limestone plants, source severity was defined as the ratio of the maximum time-averaged ground level concentration of an emission to the ambient air quality standard for criteria pollutants or to a modified TLV for noncriteria pollutants. The maximum source severity for particulates is 0.032; for free silica in the respirable particulate emissions, it is 0.12. Emissions from this industry in 1978 are estimated to be the same as they were in 1972.

Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Industrial Environmental Research Laboratory, Cincinnati, Ohio, submitted by Monsanto Research Corporation, under contract no. 68-02-1874. Includes bibliographical references. Microfiche.