Titanium dioxide (TiO2) is a natural oxide of the element titanium with low toxicity, and
negligible biological effects. The classification as bio-inert material has given the possibility to
normal-sized (>100 nm) titanium dioxide particles (TiO2-NPs) to be extensively used in food products
and as ingredients in a wide range of pharmaceutical products and cosmetics, such as sunscreens and
toothpastes. Therefore, human exposure may occur through ingestion and dermal penetration, or
through inhalation route, during both the manufacturing process and use. In spite of the extensively
use of TiO2-NPs, the biological effects and the cellular response mechanisms are still not completely
elucidated and thus a deep understanding of the toxicological profile of this compound is required. The main mechanism
underlining the toxicity potentially triggered by TiO2-NPs seems to involve the reactive oxygen species (ROS)
production, resulting in oxidative stress, inflammation, genotoxicity, metabolic change and potentially carcinogenesis.
The extent and type of cell damage strongly depend on chemical and physical characteristics of TiO2-NPs, including size,
crystal structure and photo-activation. In this mini-review, we would like to discuss the latest findings on the adverse
effects and on potential human health risks induced by TiO2-NPs exposure.