Assessing the risk of exposure of underground mine workers to respirable mine dust and diesel particulate matter hazards, a case study of Chirano Gold Mines Company Limited, Ghana

Particulate matter is a significant health hazard to many industrial workers, most especially those in the mining industry. Many underground workers globally suffer from silicosis, cancer and other health related effects due to prolonged exposure to respirable crystalline silica dust and diesel particulate matter (DPM). In order to determine the possible potential outbreak of these diseases at Chirano Gold Mines Limited (CGML), an assessment of the levels of exposure of underground mine workers to occupational respirable mine dust and DPM hazards were undertaken. The study could not take into consideration the use of respirators as a control measure thereby considering all the experimental findings as potential exposures. Gravimetric air sampling pumps were used in collecting dust and DPM samples for analysis. The respirable dust fraction were determined by the differences in weight between the empty cassette filters and the used filters whereas their crystalline silica content were determined by X-ray diffraction using National Institute for Occupational Safety and Health’s (NIOSH) analytical method 5040 as a guide. The DPM fraction of the samples was also determined using NIOSH analytical method 7500. After analysis, the results showed that the respirable dust exposures to the SEGs where far below American Conference of Governmental Industrial Hygienist’s (ACGIH) PEL of 3.0mg/m3 over a Time Weighted Average (TWA) of 8 hours. However, high crystalline silica contents were observed in some of the samples. The order of exposure to silica is presented in a descending order as follows; Jumbo operators> Cubex operators>Shotcretes operators>Solo operators>Blast men>Service men>Diamond drillers>Bogger operators>Supervisors>Truck operators. The results indicated that about 40.58% of the Sampled Exposure Groups (SEGs) recorded levels higher than ACGIH’s recommended Permissible Exposure Limit (PEL) of 0.05 mg/m3. DPM results also revealed a higher level of exposure to SEGs as 48.68%, 11.84% and 39.47% of the SEGs fell within class A, B and C respectively. Shotcrete operators recorded the maximum mean exposure level of 287.99 µg/m3 whereas truck operators recorded the minimum mean levels of 70.07 µg/m3. In a survey of 98 respondents majority of them were aware of the presence of the particulate matter hazards and its related effects. Nevertheless, a significant portion of the respondents had very little knowledge of these. The research further ascertained that well about 79.59% of the workers generally feel uncomfortable when using the FFp2 respirators during operational activities. This had a negative effect on the use of their respirators during work. High silica values in little respirable dust sampled suggests the presence of high silica bearing rocks underground thereby putting workers at risk to contracting silicosis. High DPM levels also suggest a high DPM generation by machines and equipment underground. Inefficiency of available mitigation measures other than respirators is also a factor of the high DPM exposure underground. From the study, if the current underground PM generation levels remain unchanged, then an increased risk to respiratory diseases silicosis, lung cancer as well as other related disease would occur.

Source: KNUST