Potential for Reactive-Oxygen Species (ROS) Production on Mineral Nanoparticles

Airborne particles small enough to lodge and reside within the lungs have the potential to produce reactive-oxygen species or ROS (e.g., O₂^-·, OH^·, etc.). When located in lung tissue, the organic-rich environment may create a more hydrophobic interface where radical species are favored over ionic species. These ROS can be the cause of DNA mutations and cancer. Recent work has shown that nanoparticles or ultrafines are more prevalent in airborne particulate matter than previously believed. Whether found as individual particles or as aggregates, nanoparticles could have significantly greater capacity to produce ROS than 1 micron-size particles due to their greater relative surface area and higher reactivity per square nanometer. Defects such as corner and edges on particles comprise a significant fraction of surface sites on particles 2 nm or less. Hence, assessment of ROS production capability must take into account these highly reactive sites. This work uses density functional theory (DFT) calculations to estimate the relative potentials for various nanoparticles (e.g., rutile, ferrihydrite, quartz) to produce ROS and therefore lead to deleterious health effects. Energies of formation of radical species at corner, edge and terraces are used as metrics for ROS potential formation.