Exposure assessment of respirable free silica in coal mining areas

The International Agency for Research on Cancer (IARC) has classified free silica/quartz as a Group 1 carcinogen, indicating sufficient evidence of its carcinogenicity in humans. In the present study, suspended particulate matter (SPM), respirable dust (PM10), and free silica content in dust were assessed to determine the associated exposure risk in three mega coal mines (Bharatpur, Kaniha, and Lingaraj OCP) located in the Talcher Coalfield, Odisha, India. The respirable dust samples collected on filter paper were analyzed using Fourier Transform Infrared Spectroscopy (FTIR), Powder X-ray diffraction (PXRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS) to characterize their composition and morphology. The highest concentrations of SPM and PM10 were observed at Bharatpur OCP, with mean values of 394 µg/m3 and 136 µg/m3, respectively. In contrast, Kaniha OCP exhibited slightly lower concentrations of SPM and higher concentrations of PM10, with mean values of 230 µg/m3 and 193 µg/m3, respectively. When compared with Bharatpur OCP, the highest concentration of free silica was observed at Kaniha OCP, with values ranging from 5.94 to 114.89 µg/m3 and a mean concentration of 41.59 µg/m3. The health risk assessment, conducted using USEPA methodology, indicates that Kaniha OCP poses the highest risks of exposure to respirable silica, with both non-carcinogenic and carcinogenic outcomes, followed by Bharatpur OCP. In contrast, the Lingaraj OCP exhibited comparatively lower health risk levels. The SEM/EDS analysis revealed clear evidence of respirable free silica particles at all three mining sites.