Sulphur loading of respirable and inhalable dust at a platinum smelter

Abstract

The contribution that sulphur, in the form of sulphates, has on ill health is still a focal point of many a study, especially in environmental studies depicting the effects that particulate air pollution has on health. Although the implication of sulphur on particulate matter is not yet well defined, numerous studies do state that the presence of sulphur on particulate matter contributes to poor health. Sulphur adhered to dust has been associated with cardiovascular mortality and the ability to bring about pathological lung changes, which correlate with changes seen in asthma. There are currently no information regarding the possibility of sulphur loading on particulate dust in a platinum smelter, and consequently, the associated health risk is undefined. Aim: This study aimed to quantify the sulphur content of inhalable and respirable dust in a platinum smelter, as well as to explore the possibility of a correlation between sulphur dioxide exposure and the sulphur content of dust. Method: Three potential high risk activities around the furnaces were identified, and personal sampling was conducted on workers concerned with these tasks. Multi–dust sampling was conducted using an IOM sampler (SKC®) fitted with both a MCE filter and a foam insert. Simultaneously, personal sulphur dioxide exposure was monitored using a Dräger Pac® 7000. The gross airflow direction and velocity was recorded in the proximity of the furnaces, together with relative humidity and dry bulb temperature. Area samples were also obtained with the goal of being subjected to electron microscopy and to determine the pH of the dust. Data was Box–Cox transformed to normalise the distribution, and the transformed data was used for further statistical calculations. Results: Environmental factors were similar on the different floors of the smelter. Sulphur was present on both the respirable and inhalable dust fractions, and the highest sulphur percentage was recorded on the tapping floor. The sulphur content of respirable dust was significantly higher (p = 0.03) than the sulphur content of the IOM foam dust (inhalable and thoracic portion combined). A medium correlation with statistical significance was obtained between respirable sulphur and the SO2 concentration of the ceramic workers (r = 0.27; p < 0.05), as well as the foam sulphur and the SO2 concentrations of the paste loaders (r = 0.32; p < 0.05). No significant correlation could be found between SO2 concentrations and sulphur content of particles when all the samples were considered. Conclusion: Environmental differences recorded on the different floors did not significantly influence sulphur loading. Sulphur contained in smaller particles (respirable dust) is significantly higher than that of the larger particles sampled possible because of an increase in oxidation of SO2 due to an increase in surface area available for sulphur loading in the smaller aerodynamic fraction. The sulphur could however also be attributed to the escape of sulphur containing iron pyrite via the electrodes.