Toxicity of Nano-Titanium Dioxide (TiO2-NP) Through Various Routes of Exposure: a Review

Abstract

Nano-titanium dioxide (TiO2) is one of the most commonly used materials being synthesized for use as one of the top five nanoparticles. Due to the extensive application of TiO2 nanoparticles and their inclusion in many commercial products, the increased exposure of human beings to nanoparticles is possible. This exposure could be routed via dermal penetration, inhalation and oral ingestion or intravenous injection. Therefore, regular evaluation of their potential toxicity and distribution in the bodies of exposed individuals is essential. Keeping in view the potential health hazards of TiO2 nanoparticles for humans, we reviewed the research articles about studies performed on rats or other mammals as animal models. Most of these studies utilized the dermal or skin and the pulmonary exposures as the primary routes of toxicity. It was interesting that only very few studies revealed that the TiO2 nanoparticles could penetrate through the skin and translocate to other tissues, while many other studies demonstrated that no penetration or translocation could happen through the skin. Conversely, the TiO2 nanoparticles that entered through the pulmonary route were translocated to the brain or the systemic circulation from where these reached other organs like the kidney, liver, etc. In most studies, TiO2 nanoparticles appeared to have caused oxidative stress, histopathological alterations, carcinogenesis, genotoxicity and immune disruption. Therefore, the use of such materials in humans must be either avoided or strictly managed to minimise risks for human health in various situations.

Autism genes are selectively targeted by environmental pollutants including pesticides, heavy metals, bisphenol A, phthalates and many others in food, cosmetics or household products

“…Such treatment results in smaller uteri and foetuses [248]. Titanium dioxide nanoparticles accessing the nasal or pulmonary route are also translocated to the brain or the systemic circulation and thence to other organs [249]. The prenatal administration of titanium dioxide nanoparticles in rats increases frontal cortical and neostriatal dopamine levels in the offspring [250] and modifies the expression of neurodevelopmental genes in the brains of the young offspring in mice [251] .…”

Overview of the toxic effects of titanium dioxide nanoparticles in blood, liver, muscles, and brain of a Neotropical detritivorous fish

“…Recently, the Committee for Risk Assessment from the European Chemicals Agency (ECHA) classified titanium dioxide as a substance suspected of causing cancer (category 2) through the inhalation route in mammals due to their low solubility and bio‐persistency, which lead to inflammation and oxidative stress . Most toxicological studies with TiO 2 ‐NP have been done in mammals or small organisms such as Daphnia . Few studies though focus on fish, and most of them are restricted to a few model species like zebra fish, trout, or carp .…”

Titanium release in peri‐implantitis

“…The high levels of Ti found in the present study are suggested to derive from the peri‐implant pretreatment. Ti may be found at low concentrations in periodontitis tissue due to exposure to Ti dioxide from toothpaste, food or environmental exposure (eg, cosmetics) …”