Comparative evaluation of the performance of aerosol samplers for the assessment of soluble platinum exposure
Ramotsehoa, Motsheoa Cynthia
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The primary focus of this study was to compare the efficiency of six filter samplers in the collection of inhalable soluble platinum (Pt) salts at a South African base metal refinery. Inhalation remains the major route of occupational exposure to platinum groups metals (PGMs). South Africa would benefit from the study since it’s amongst the major countries where PGMs are produced and hence, monitoring of worker exposure with the most efficient sampler is of utmost importance. The IOM is currently being used in routine exposure monitoring although no studies have been carried out to compare its performance to that of the other samplers under the actual base metal refinery conditions. Method: The button, closed face cassette (CFC), Gesamtsstaubprobenhome (GSP), (Institute of Medicine) IOM, PAS-6 and seven hole (SH-sampler) samplers were randomly allocated to six different positions in presumably high exposure areas. The samplers were moved around in the subsequent sampling days and the process repeated 3 times. The average dust mass and Pt concentrations were used as a basis of sampler performance and comparisons from which sampler hierarchies were determined. Results: The average relative humidity ranged between 37% and 43% and the average dry bulb temperature of 22.4°C was measured. Comparison of the dust mass concentrations revealed no statistically significant differences amongst the six filter samplers tested. The SH-sampler and CFC however collected the highest and lowest dust mass and Pt concentrations respectively. Discussion: The SH-sampler was found to be a sampler with more reliability than the the IOM for the collection of dust mass and soluble Pt. The IOM collected 98% of the SH-sampler dust mass and Pt concentrations. This was in spite of the larger variations indicated by the highest relative standard deviations and confidence intervals shown by the IOM than the other samplers. The GSP sampler, however, showed better precision than all the other samplers in the collection of platinum. The seven 4 mm orifices of the SH-sampler sampler allow for uniform distribution of sampled particles onto the filter supporting its better precision than the IOM which has only one 4 mm opening. The worst performing sampler was the CFC sampler since it collected the lowest dust mass and Pt concentrations. The CFC and the PAS samplers have downward facing inlets that are affected by gravity especially in lower wind speeds which, therefore, influences their efficiency. The GSP sampler concentrations placed it as 4th and 3rd best in Pt and dust mass hierarchies respectively even though it showed better precision than SHS in the sampling of Pt. The button sampler did not perform as well as would have been expected considering that its many evenly spaced orifices and the stainless steel are meant to reduce sample losses. Conclusion: The sampler hierarchy according to dust mass concentrations was in the following order: SH-sampler, IOM, PAS, GSP, button and CFC. The hierarchy obtained from Pt concentrations gave the order as SH-sampler, IOM, GSP, button, PAS and CFC. Similar studies have to be undertaken in primary and secondary platinum workplaces to validate the study results. Such studies should compare better performing samplers (SHS, IOM, Button and GSP) as well as incorporate particle size determination and distribution in those areas.
- Health Sciences