Introduction It is well established that gold mine dust is a major cause of pneumoconiosis and other lung diseases. The main sources of dust in gold mines are well documented. Rock drill operators using pneumatic percussion rock drills are at the sharp end of exposure due to the very nature of the drilling process in that rock is pulverized and liberate large amounts of dust even with the addition of copious amounts of water. Historically it has been found that the gold bearing rock formations in South Africa typically contain about 30% quartz. (1) Keeping this in mind, the potential for overexposure is obvious. The actual exposure of rock drill operators to dust and quartz is not well documented and for this reason this research focuses on this particular occupation. Objectives To measure the respirable dust and quartz exposure of Rock Drill Operators in two typical gold mines in the Free State province of South Africa in 2007. Methods
This study is a descriptive, cross sectional, rapid assessment based on the findings of gravimetric sampling results taken at Rock Drill Operators working underground on two different gold mines. The actual gravimetric sampling was done in accordance with NIOSH methodology. The study population consisted of 30 Rock Drillers on one mine and another 30 on a second mine. The Rock Drill Operators was randomly selected using their company numbers and selected by the “Excel” program random number selection function. Ordinary gravimetric sampling, using Gillair pumps, was used and weighing done on the mine by a qualified and well experienced Air Quality Analyst using an appropriate methodology compatible with international best practices. Quartz analysis was done at the National Institute for Occupational Health (NIOH) in Johannesburg using a Phillips X-Ray diffraction. (Photo 2). The methodology used by the laboratory technician is conducted strictly according to the manufacturer’s specifications and in line with international best
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practices. This laboratory participates in quality assurances programmes and is highly regarded internationally. Results The initial hypothesis that exposure underestimation in the past in terms of this particular occupation is confirmed and could be contributable to the difficulties typically experienced when using the traditional gravimetric sampling method. The average quartz percentage was determined to be 25.45% for mine 1 and 38.49% for mine 2 giving an average of 30.67% for both mines. The Total Mass means was 0.73 and 0.23 mg for mine 1 and 2 respectively with an average for the two mines being 0.49 mg. Results for Time Weighted Averages revealed values of 0.69 and 0.22 mg/m3 for mine 1 and 2 respectively with an average of 0.46 mg/m3 for both. In terms of Air Quality Index (AQI) the values were 1.4 and 0.6 for mine 1 and 2 respectively with an average for both mines therefore being 1.1. A comparison with the South African OEL for quartz showed overexposure on 32% of all rock drill operators sampled. When using the NIOSH OEL that figure is even worse at 72%. Based on these results it would thus be fair to conclude that Rock drill operators working without appropriate respiratory equipment will be overexposed and therefore potentially suffer ill health as a result. Discussion and conclusion
Rock drill operators are potentially exposed to high levels of harmful dust and quartz in their normal daily work if not adequately protected using good, effective appropriate and comfortable respiratory protective equipment (RPE) and additionally having proper ventilating velocity. At an average Air Quality Index (AQI) of 1.1, it would require the mine Occupational Hygienist to immediately institute remedial action in conjunction with an investigation to determine the reasons for such overexposure. The AQI of 1.46 and 0.6 for Mine 1 and 2 respectively curiously beg the question as to why there is a difference. The answer unfortunately is not clear at first glance as both mines wetted the stope working faces equally well, ventilates the faces with similar velocities
which in turn alludes to similar dilution factors but the only reasonable deduction that could be made is that high TWA respirable quartz pollutant concentrations (mg/m3) values in lots of cases corresponded with low actual quartz values. This could be co-incidental but in fact caused the TWA graph to be inversely proportional to the AQI graph. Couple this to the fact that the actual dust burden is lower in Mine 2 compared to Mine 1 as confirmed by the TWA values obtained, then the results becomes easier to interpret. However, the assumption is made that the TWA values should enjoy more preference in the analytical sense as it could be compared directly to OEL’s which serves to highlight the hypothesis very clear in that rock drill operators are over exposed to a high degree of certainty which in turn concurs with other research done in the past.
The fact that the methods used to drill holes in order to be charged up with explosives has largely remained unchanged for more decades in the mining industry with no viable alternative on the horizon, emphasizes the fact that focused attention and proper risk assessment is called for to protect rock drill operator from harmful exposure. That said the normal paper dust mask cannot in all good conscience be regarded as appropriate RPE for this occupation. The aforementioned risk assessment must determine and ultimately classify which occupations would benefit from “upgrading” to better quality dust masks. To accept only one type of dust mask on a mine would be considered a travesty and contrary to the application of all good occupational hygiene principles. Failing to expedite the aforementioned risk assessment on RPE per occupation will result in failure to place effective safeguard measures in place to protect rock drill operators from harmful dust and will mean that their health will be compromised in time. The development of air line fed type hard hats incorporating a face shield, harness fitted with moisture trap, filter and a snap fit attachment to a compressed air line is likely to be the ultimate solution provided that it is light, comfortable and the introduction is done in a manner that will ensure the understanding in the benefits to be derived from using such a device in the place of ordinary dust masks by Rock
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Drill Operators. Ultimately, using the Occupational Hygiene hierarchy of control that dictates the first consideration of such control being elimination, coupled with the horrendous ergonomic problems faced by rock drill operators, the solution seems to point inevitably towards meganisation. Using a person in the same homogeneous exposure group (HEG) as that of the rock drill operator as a forced alternative is not advisable as the exposure of a rock drill operator is very unique and certainly not comparable to that of a winch driver for example. The wet environment certainly warrants the investigation into alternative methods for sampling as normal, traditional methods proved to be inconsistent, unreliable and often unusable.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/7281 |
| Date | 16 September 2009 |
| Creators | Kemsley, Daniel Michel |
| Source Sets | South African National ETD Portal |
| Language | Spanish |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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