Exposure of vehicle operators to vibration and noise at a Tanzanian opencast goldmine
Schmidt, Brian Ronald
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In this study the exposure of mining vehicle operators, on an opencast goldmine in Tanzania, to certain hazards specific to their occupation was assessed. The aim was to quantify these levels of exposure in order to estimate the risk of health effects but also to report levels of these hazards that exist on mining vehicles. Three different hazards with different physiological effects were assessed and it included exposure to whole-body vibration, A-weighted noise and low frequency noise. In each case correctly calibrated instrumentation was used and internationally accepted methods were followed. It was found that mining vehicles commonly exposed operators to levels of whole-body vibration within and above the ISO Health Guidance Caution Zone (HGCZ) and above the ropean action level, which indicates the need for intervention and control. These levels are a cause for concern and will likely lead to health effects. Noise that damages human hearing (A-weighted noise) was present in high levels on mining vehicles, in each case being higher than the permissible exposure limit of 85 dB(A). Thus operators of mining vehicles are exposed to noise levels that will damage their hearing in time. A potential hazard in the occupational world, low frequency noise, was also included in the assessment. Literature indicates that low frequency noise is capable of causing many human health effects and thus levels on mining vehicles were reported in order to give an indication of what levels may be expected in this department of mining. It was found that much of the sound energy measured on vehicles was located in the low frequency range. In the lowest frequency band measured, Leq levels of more than 100 dB(Z) were commonly found. Controls should be implemented as far as is reasonably practicable to ensure that operators are not exposed above recommended or permissible levels for each hazard. These controls can include good maintenance of vehicles and roads to reduce whole-body vibration, sound proofing of vehicle cabs along with hearing protection devices to protect hearing and further research regarding the exposure and health effects caused by low frequency noise. Following literature indicating the physiological effects of low frequency noise exposure and also the presence thereof in different occupations, it is concluded that A-weighted noise measurements alone can not be used when quantifying the risk involved in a given acoustical environment.
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