A review published in 2022 in the journal NanoImpact evaluated the latest research related to genotoxic effects of titanium dioxide through in vivo studies and in vitro cell tests. Researchers summarized the results by stating TiO2 nanoparticles “could induce genotoxicity prior to cytotoxicity,” and “are likely to be genotoxic to humans.”

TiO₂ comes in many different forms. However, only a few of these forms are considered food-grade (acceptable to be added to food). Many studies that raised concern about the safety of TiO₂, including the concern for genotoxicity, used forms of TiO₂ that are not considered acceptable for use in food and have different properties than food-grade TiO₂. Other studies did use food-grade TiO₂, but took steps to break the material down into smaller particles than what would normally be found in food.

You can find more information about EFSA’s work in the area of food additives on our website

TiO₂ comes in many different forms. However, only a few of these forms are considered food-grade (acceptable to be added to food). Many studies that raised concern about the safety of TiO₂, including the concern for genotoxicity, used forms of TiO₂ that are not considered acceptable for use in food and have different properties than food-grade TiO₂. Other studies did use food-grade TiO₂, but took steps to break the material down into smaller particles than what would normally be found in food.

In a 2020 study published in the Journal of Trace Elements in Medicine and Biology, researchers conducted an in vitro experiment to analyze the effects of TiO2 nanoparticles on a human neuroblastoma (SH-SY5Y) cell line. The scientists evaluated “reactive oxygen species (ROS) generation, apoptosis, cellular antioxidant response, endoplasmic reticulum stress and autophagy.” The results showed that exposure to the nanoparticles “induced ROS generation in a dose dependent manner, with values reaching up to 10 fold those of controls. Nrf2 nuclear localization and autophagy also increased in a dose dependent manner. Apoptosis increased by 4- to 10-fold compared to the control group, depending on the dose employed.” 

Absorption

It’s true that titanium dioxide does not rank as high for UVA protection as zinc oxide, it ends up being a small difference (think about it like being 10 years old versus 10 years and 3 months old). This is not easily understood in terms of other factors affecting how sunscreen actives perform (such as the base formula), so many, including some dermatologists, assume that zinc oxide is superior to titanium dioxide for UVA protection. When carefully formulated, titanium dioxide provides excellent UVA protection. Its UVA protection peak is lower than that of zinc oxide, but both continue to provide protection throughout the UVA range for the same amount of time.