Comparative Analysis of Titanium Dioxide, Iron Oxide, and Zinc Oxide Nanoparticles: Exposure Risks and Toxicity

Nanoparticles (NPs), characterized by their nanoscale size (1–100 nm) and unique physicochemical properties, have garnered significant attention for their applications in various fields, including medicine, electronics, and environmental remediation. These materials exhibit enhanced durability, flexibility, and reactivity due to their high surface area-to-mass ratio and small size. While nanoparticles occur naturally through events like wildfires and volcanic eruptions, anthropogenic sources such as welding, combustion, and industrial activities have contributed to increased environmental and human exposure. The aging processes of nanoparticles, such as aggregation, disaggregation, and chemical transformation, further influence their fate and toxicity. This review focuses on the comparative toxicity of three widely used nanoparticles: titanium dioxide (TiO₂), iron oxide (Fe₂O₃), and zinc oxide (ZnO). Despite their varied applications, these nanoparticles share a common ability to enter the human body through inhalation, ingestion, and dermal exposure, often accumulating in vital organs such as the liver, spleen, and brain. Zinc oxide nanoparticles exhibit significant toxicity due to ion release and the generation of reactive oxygen species (ROS), leading to oxidative stress and cellular damage. In contrast, titanium dioxide nanoparticles, although largely inert, show size-dependent toxicity and potential genotoxic effects at the nanoscale. Iron oxide nanoparticles, generally considered biocompatible, may induce oxidative stress at high concentrations but display comparatively lower toxicity. The toxicity of nanoparticles is influenced by their size, shape, surface modifications, and interaction with biological systems. Coating strategies, such as polymer or amino acid functionalization, can enhance solubility and biocompatibility while reducing adverse effects. This comparative evaluation underscores the need for further research into the long-term implications of nanoparticle exposure, highlighting the importance of developing safer nanomaterials and robust toxicity assessment frameworks.