Exposure profile of respirable crystalline silica in stone mines in India.

Silicosis is one of the major occupational lung diseases among stone miners; currently, it is a major concern in India given its 12-30% prevalence. The objective of this study was to determine the exposure profile of respirable dust and crystalline silica concentrations from sandstone, masonry stone, and granite stone mines in India. Personal respirable dust samples were collected from each type of mine and analyzed for dust and respirable crystalline silica concentrations. The mean dust concentrations were found to be 0.47 mg/m, 1.24 mg/m, and 3.28 mg/m for sandstone, masonry stone, and granite stone mines, respectively. The mean respirable crystalline silica concentrations were 0.12 mg/m for sandstone mines and 0.17 mg/m for masonry stone and granite stone mines. The concentrations in sandstone mines was below the standard stipulated by the Directorate General of Mine Safety in India (0.15 mg/m), whereas in the granite and masonry mines the concentrations just exceeded the limit. The Indian standard for respirable crystalline silica is three to six times higher than the standard set elsewhere (i.e., by OSHA, ACGIH, and Egyptian Labor Law standards). Considering the large number of silicosis cases among stone miners in India, the present standard appears inadequate. It is recommended that the standard be lowered to match international standards that minimize the risk of silicosis.