Monitoring and Assessment of Airborne Respirable Limestone Dust and Free Silica Content in an Indian Mine

BACKGROUND. Dust exposure and its related harmful effects on miners is a serious health issue. OBJECTIVES. The present study was undertaken to identify respirable dust concentrations and free silica content in 24 dust samples collected from a limestone mine during pre-monsoon and post-monsoon seasons. METHODS. Time-weighted average (TWA) dust concentrations were calculated for 8-hour work shifts followed by determination of free silica concentration using the Fourier transform infrared spectroscopy technique. RESULTS. The TWA dust concentration for personal and area dust samples during September 2013 was found to be in the range of 0.32–1.04 mg/m(3) and 0.25–0.54 mg/m(3), respectively. For February 2014, the TWA dust concentration was between 0.62–1.23 mg/m(3) for personal samples and 1.04–2.64 mg/m(3) for area samples. Samples collected in February 2014 had marginally higher values of dust levels in the air of the mine compared to September 2013. The highest dust concentration was found to be 1.23 mg/m(3) for a drill operator and 2.64 mg/m(3) at the crusher belt conveyor junction. The average free silica percent for the samples collected in February 2014 was 1.73%, which was almost double compared to September 2013 (0.87%). CONCLUSIONS. In both seasons, personal dust samples had higher free silica content than area dust samples. Even though dust concentrations were below the permissible limit, workers had widely different exposures, hence many of them may be at risk of pneumoconiosis when exposure is prolonged. PARTICIPANT CONSENT. Obtained COMPETING INTERESTS. The authors declare no competing financial interests.