Occupational exposure to particulate matter in three Indian opencast mines

Exposure of mine workers to particulate matter ( PM) in opencast mines is of major concern because of associated adverse health impacts. Dispersion of PM in such mines depends on their design and local meteorological conditions. With an increase in depth of mines, efficient vertical movement and the dispersion of PM away from mine working area become difficult. Therefore, studies on dispersion behavior of PM in opencast mines are needed. Measurements of PM concentration have been carried out in three opencast mines in India: (i) Malanjkhand Copper Project (MCP), (ii) Kiriburu Iron Ore Mine (KIOM), and (iii) Meghahatuburu Iron Ore Mine (MIOM). A total of 20 days of monitoring of PM and local meteorology were carried out in these three mines. The aims were to investigate the following: (i) vertical PM concentration profiles at different depths during mining operation, (ii) particle travel time and its relationship with mine depth, (iii) particle mass balance in terms of the dispersion and settling proportion, and (iv) the relationship of particle concentration with depth as it moves downward. Results show that the inhalable PM (10-20 mu m) were similar to 22 and 36 % higher than the thoracic (4-10 mu m) and alveolic (< 4 mu m) fractions of PM, respectively. Travel times of PM from similar to 10 m mine depth to surface are measured up to 17and 13 min for the KIOMand MIOM, respectively. Travel time was as high as similar to 1 h at MCP for source (workplace where mining operations are taking place) at a depth of 168 m. An empirical equation (R=0.746, p=0.034) showing relationship between particle travel time and depth is developed. About 23-39 % inhalable, 19-37 % thoracic, and 9-30 % alveolic PM settled inside the mine within a vertical distance of 18-20 m from the source and 30-47 % inhalable, 31-51 % thoracic, and 34-54 % alveolic PM escaped from the mine. The empirical equations for downward movement of PM predicted particle concentrations between 88 and 91% of the measured value at 10m depth and 75 and 95 % at 40 m. The findings of this work are important in understanding dispersion of occupational PM at the worksite and the associated exposure of mine workers.