Exposure of workers to ammonia and oxides of nitrogen from blasting fumes in an underground mining setup
Cronje, Daniel Christiaan
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There is limited information available on the exposure of workers to NOx and NH3 from blasting fumes in the underground mining setup. This study is therefore motivated to improve the working conditions of underground mine workers handling these explosives, thus minimizing their potential exposure to NOx and NH3. Only a few epidemiological studies are available addressing the cumulative exposure of underground mine workers to blasting fumes, as well as the incidents of so–called gassing cases, although such cases do occur on a regular basis in an underground mining setup. Underground mine workers undertaking handling, transportation and charge up of explosives are potentially exposed to blasting fumes on a daily basis and cumulative exposure is therefore a major risk factor and could lead to serious health effects. The Mine Health and Safety Regulations of the Mine Health and Safety Act (Act No. 29 of 1996) has recommended limits for the components of blasting fumes, but there is an absence of a limit specifically set for blasting fumes as a single gas exposure. In blasting fumes there are mixtures of gases that can cause respiratory and systemic health effects at much lower levels. To determine the exposure of underground mine workers to NOx and NH3 from blasting fumes and ANFO, samples were taken for a period of three hours and then time weighted to an 8–hour time weighted average (TWA) and compared to existing standards. Active sampling and passive diffusive sampling were conducted to determine the difference of occupational exposure levels to NOx and NH3 among underground mine workers and surface workers. Samples were taken 12 hours after the previous blast due to work related limitations making it impossible to sample night shift workers. Active sampling for a duration of 180 minutes, time weighted to an 8–hour exposure, indicated that occupational exposure to blasting fumes of underground mine workers responsible for charge up did not exceed the OELs of the Regulations of the Mine Health and Safety Act (Act No. 29 of 1996). Passive diffusive sampling for a duration of 180 minutes, time weighted to an 8–hour exposure, indicated that occupational exposure to blasting fumes of three underground mine workers responsible for charge did exceed the OELs of the Regulations of the Mine Health and Safety Act (Act No. 29 of 1996).. There was a significant positive correlation between personal exposures to NH3 between the two measurement methods. There was a positive, insignificant correlation, as well as a strong agreement between personal exposures to nitrogen dioxide (NO2). This correlation proved that any of these two approved conventional measurement methodologies could be used to determine the exposure of underground mine workers to NH3 or NO2. Limitations of the study as well as recommendations for future studies are also presented in Chapter 5. This study however does not exclude the effect of cumulative exposure to blasting fumes over an extended period of time. Short term exposure is also a major concern when working with toxic fumes and should be determined in future studies.
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