Titanium dioxide (TiO₂) nanoparticles (NPs) are widely used in various applications, but their toxicological effects are not fully understood. This review summarizes current knowledge on the toxicology of TiO₂ NPs, highlighting the importance of inhalation as the primary exposure route in the workplace. TiO₂ NPs can translocate to systemic organs from the lungs and gastrointestinal tract, though the rate is low. Oral exposure occurs mainly through food products containing TiO₂ NP-additives, while dermal studies show that TiO₂ NPs do not penetrate the stratum corneum. In nanomedicine, intravenous injection can deliver TiO₂ NPs directly into the body, causing pathological lesions in the liver, spleen, kidneys, and brain. However, these effects may be due to high doses. There is a lack of epidemiological data on TiO₂ NPs, but long-term inhalation studies in rats have reported lung tumors. The review discusses the physicochemical properties of TiO₂ NPs, their different behavior compared to fine particles (FPs), and their potential for human and environmental exposure. It also covers exposure routes, toxicokinetics, and the distribution, metabolism, and excretion of TiO₂ NPs. The toxic effects of TiO₂ NPs include acute toxicity, which is currently not well understood in humans, but studies in animals show that inhalation can cause pulmonary inflammation. The review emphasizes the need for further research to assess the risks of TiO₂ NPs and to develop appropriate exposure limits.Titanium dioxide (TiO₂) nanoparticles (NPs) are widely used in various applications, but their toxicological effects are not fully understood. This review summarizes current knowledge on the toxicology of TiO₂ NPs, highlighting the importance of inhalation as the primary exposure route in the workplace. TiO₂ NPs can translocate to systemic organs from the lungs and gastrointestinal tract, though the rate is low. Oral exposure occurs mainly through food products containing TiO₂ NP-additives, while dermal studies show that TiO₂ NPs do not penetrate the stratum corneum. In nanomedicine, intravenous injection can deliver TiO₂ NPs directly into the body, causing pathological lesions in the liver, spleen, kidneys, and brain. However, these effects may be due to high doses. There is a lack of epidemiological data on TiO₂ NPs, but long-term inhalation studies in rats have reported lung tumors. The review discusses the physicochemical properties of TiO₂ NPs, their different behavior compared to fine particles (FPs), and their potential for human and environmental exposure. It also covers exposure routes, toxicokinetics, and the distribution, metabolism, and excretion of TiO₂ NPs. The toxic effects of TiO₂ NPs include acute toxicity, which is currently not well understood in humans, but studies in animals show that inhalation can cause pulmonary inflammation. The review emphasizes the need for further research to assess the risks of TiO₂ NPs and to develop appropriate exposure limits.