MINERAL-INDUCED REACTIVE OXYGEN SPECIES RESEARCH IN THE CONTEXT OF MEDICAL GEOLOGY: AN UPDATE

Over the last decade our group at Stony Brook University has been focussed on understanding the processes and conditions that lead to the spontaneous formation of Reactive Oxygen Species (ROS). ROS are oxygen-containing radicals (superoxide, O2*^-; hydroxyl radical, OH*) and hydrogen peroxide, H₂O₂. Hydroxyl radical is the most reactive species among ROS. The most important pathway for the formation OH* is the Fenton reaction, a reaction between a reduced metal ion, often iron(II) species, and H₂O₂. Early work in our group showed that pyrite forms OH* spontaneously in solution when the mineral is dispersed in aerated aqueous solutions. Development of several methods for the detection of OH* and H₂O₂ in mineral slurries enabled us to demonstrate that other minerals, such as chalcopyrite, olivine, and bornite also produce ROS. Methods were also developed to determine the effect of mineral exposure on the viability of human epithelial cells and the generation of ROS within these cells.

Our latest work has been focussed on understanding synergistic effects between pairs of minerals and pairs of dissolved ions. Our research has uncovered that the production of ROS is enhanced when pyrite and chalcopyrite are both present in dispersions. This notion has led to detailed studies of the mechanism of this interaction. Related to the work on pyrite and chalcopyrite, we have conducted research on the effect of co-exposure to copper(II) and iron(II) ions. This work, enabled by the use of an electrochemical probe to determine H₂O₂ in real time in complex fluids, shows that the presence of iron(II) ions can lead to the reduction of copper(II) to copper(I). In addition, we are seeing evidence for metal-ion-complex-mediated oxidation of organic compounds in simulated lung fluid. This process leads to the spontaneous formation of H₂O₂ and can lead to a sustained mineral-related health burden.