Abstract
Fine/micron-sized iron oxide particulates are incidentally released from a number of industrial processes, including iron ore mining, steel processing, welding, and pyrite production. Some research suggests that occupational exposure to these particulates is linked to an increased risk of adverse respiratory outcomes, whereas other studies suggest that iron oxide is biologically benign. Iron oxide nanoparticles (IONPs), which are less than 100 nm in diameter, have recently surged in use as components of novel drug delivery systems, unique imaging protocols, as environmental catalysts, and for incorporation into thermoplastics. However, the adverse outcomes associated with occupational exposure to IONPs remain relatively unknown. Relevant in vivo studies suggest that pulmonary exposure to IONPs may induce inflammation, pulmonary fibrosis, genotoxicity, and extra-pulmonary effects. This correlates well with in vitro studies that utilize relevant dose, cell type(s), and meaningful end points. A majority of these adverse outcomes are attributed to increased oxidative stress, most likely caused by particle internalization, dissolution, release of free iron ions, and disruption of iron homeostasis. However, because the overall toxicity profile of IONPs is not well understood, it is difficult to set safe exposure limit recommendations that would be adequate for the protection of at-risk workers. This review article will focus on known risks following IONPs exposure supported by human, animal, and cell culture-based studies, the potential challenges intrinsic to IONPs toxicity assessment, and how these may contribute to the poorly characterized IONPs toxicity profile.
Highlights
The field of nanotechnology is expanding rapidly as scientists and engineers continue to develop innovative applications using nano-scaled materials
Eight weeks post-exposure, the gpt delta mice had increased gpt mutations, lipid peroxidation-related DNA adducts, inflammatory cell infiltration, and the formation of focal granulomas [33]. These results clearly indicate the potential for Iron oxide nanoparticles (IONPs) to induce genotoxicity, even within a very short time frame, and at a relatively low dose
Prevailing information on the toxicity of IONPs suggests potential risk associated with exposure, including inflammation, fibrosis, genotoxicity, and extra-pulmonary effects, all of which have been attributed to increased oxidative stress following exposure
Summary
The field of nanotechnology is expanding rapidly as scientists and engineers continue to develop innovative applications using nano-scaled materials. Iron oxide nanoparticles (IONPs) have been developed for use in targeted cancer treatment, new imaging techniques, and as environmental catalysts due to their unique paramagnetic properties [1]. They can be incorporated into thermoplastics and other materials due to their pigmented properties, as well [2]. Iron oxide particulates (both fine/micron- and ultra-fine/nano-sized) are known to become aerosolized during. Representative epidemiology studies will be used to highlight potential adverse outcomes induced by IONPs exposure based on fine/micron-sized iron oxide reports (summarized in Table 1), followed by in vivo and in vitro studies to better ascertain IONP-induced adverse outcomes, as well as the potential underlying mechanism. This review is not meant to be a comprehensive review of IONPs toxicity literature, but rather a critical evaluation of the literature that does exist, and why so much of it appears to be conflicting
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