Abstract
Background and Objective: Silica dust is present in almost all mining operations and can cause various health problems such as silicosis in workers. The present study aimed to determine the total and respirable dust levels and the crystalline silica content of the soil in the breathing zone of workers in Iranian mines. Methods: This cross-sectional study was carried out in 2016-2017 on six Iranian silica mines. Dust sampling was performed according to the National Institute of Occupational Safety and Health (NIOSH) method No. 0600. The samples were collected from the respiratory zone of workers at 114 stations in different units of the mines. The silica content was measured using the standard NIOSH method No. 7601. The crystalline silica content in bulk samples collected from the soil was determined by using the X-Ray Diffraction (XRD) spectroscopy method. Results: The highest concentration of crystalline silica dust was 2.81±0.49 mg/m3 and was observed in the air of crushing unit of mine no. 6, and the lowest was 0.08±0.208 mg/m3 and was measured in the management/administration unit of mine no.1. The mean silica content in the solid surface of the mines was 91%. The total and respirable dust levels in all units of the mines except management/administration were higher than the permissible limit. The free silica content of all collected samples was substantially higher than the permissible limits, and in some cases, it was as much as 100 times above the standard level, which reflects the extremely high risk of working in these mines. Conclusion: Exposure of workers with crystalline silica dust in all units was higher than the standard recommended limits. It is imperative to adopt immediate measures based on technical, managerial, and personal protection solutions to reduce the exposure of workers to silica.
Highlights
Tens of thousands of Iranians work in the mining sector and this number is growing every day
The measurements made in six Iranian silica mines showed that the highest total and respirable dust levels belonged to crushing units and the lowest levels were related to management/administration units
In a study conducted by Hayumbu et al (2008) on two mines in Zambia, the silica levels in these mines were 59% and 26%, and the quantity of free silica dust was 0.992 and 0.888 mg/m3, which are all higher than the permissible exposure limit, but are still significantly lower than the silica dust levels observed in the present study
Summary
Tens of thousands of Iranians work in the mining sector and this number is growing every day. Silica or Silicon dioxide (SiO2) is an inorganic compound composed of an atom of silicon and two atoms of oxygen. It is colorless, odorless, and non-combustible and constitutes about 25% of the Earth’s crust. There are several forms of crystalline silica, which include α-quartz, quartz, tridymite, cristobalite, keatite, coesite, stishovite and moganite (Nguyen et al, 1992). Silica dust is present in almost all mining operations and can cause various health problems such as silicosis in workers. The present study aimed to determine the total and respirable dust levels and the crystalline silica content of the soil in the breathing zone of workers in Iranian mines
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