The potential health challenges of TiO₂ nanomaterials

Titanium dioxide (TiO₂) nanomaterials (NMs) have found widespread applications owing to their attractive physical and chemical properties. As a result, the potential adverse impacts of nano-TiO₂ exposure on humans have become a matter of concern. This review presents the state-of-the-art advances on the investigations of the adverse effects of NMs, including the potential exposure routes of nano-TiO₂ (e.g. respiratory system, skin absorption and digestive system), the physico-chemical characterizations of nano-TiO₂ (e.g. crystal structure, shape,size, zeta potential, treatment media, aggregation and agglomeration tendency, surface characteristics and coatings), risk evaluation of nanotoxicity (e.g. cytotoxicity, ecotoxicity, phototoxicity, and phytotoxicity) and potential mechanisms of adverse effects (e.g. generation of reactive oxygen species, oxidative stress and organelle dysfunction). The review aims to facilitate scientific assessments of health risks to nano-TiO₂, which would guide the safe applications of NMs in our daily life.