The subjects for the study were divided into two groups. (I) Mine and quarry workers with a history of 10–15 years of occupational silica exposure (n = 45) and (II) age-matched healthy control subjects (n = 20) with no known exposure to cytotoxic or genotoxic agents. The chosen 45 subjects were workers in small mines and quarries; their type of work was stone crushing, grinding, carrying chips, and extracting brick earths. All the subjects were from same area. Several mines are situated in a cluster within 2 km of one another. Informed consent was obtained after the nature of the procedure was fully explained.