Application of simulated lung fluid analysis to characterize the influence of smelter activity on the respiratory bioaccessibility of nickel-bearing soils in Kalgoorlie, Western Australia

Abstract

The city of Kalgoorlie in Western Australia has been labeled an “asthma hot spot” attributed to mining activity, prompting further investigation into toxic elements (Lee et al., 2006). Inhalation of nickel-bearing particles is a particular concern due to the presence of a nickel smelter 10km upwind of the city. The toxicological properties of nickel are well-documented, thus the primary objective is the characterization of phases identified as problematic in the lungs. To determine the smelter’s influence on nickel bioaccessibility in the soils throughout the city of Kalgoorlie, surface soil samples were taken from areas within the city and compared to soils near the smelter and outside the city, distant from the smelter. Soils were sieved to isolate the respirable fraction (<10um) potentially associated with lung disease and analyzed using a simulated lung fluid to determine the concentration of nickel soluble in the lungs. The soluble nickel represents the fraction that may be involved in allergic or asthmatic reactions, while the insoluble compounds may be of concern as some are carcinogenic. Further soil characterization was done using a six step sequential extraction and mineralogical analysis to identify nickel-bearing minerals. The influence of the smelter activity on nickel bioaccessibility in the soils within Kalgoorlie is low, but soils near the smelter host significantly higher nickel concentrations and higher bioaccessibility. Respiratory nickel bioaccessibility in soils ranges from 1 to 3% in and outside the city of Kalgoorlie, while the area surrounding the smelter increases to up to 6.8%. In each case, there is a direct correlation between bioaccessibility percent and percent nickel bound in the water-soluble and exchangeable fractions, but the simulated lung fluid dissolves more nickel in each sample than is present in these two fractions, potentially due to the presence of weak chelating agents in the solution. Respiratory bioaccessibility is low in Kalgoorlie soils because nickel occurs primarily in sulfides, with minor oxides and silicates, all relatively insoluble in lung fluid. However, the high concentrations of these compounds could be of concern, as they are potential carcinogens at high concentrations. Lee, Y.P., Cook, A., Thompson, P., Weinstein, P. 2006. Epidemiology. 17(6):283-284