The toxicity of P25TiO₂NPs under UV radiation could be even higher when combined with other usual components of sunscreens Indeed, Soler de la Vega et al. advise that combination with parabens increases the toxicity of the final cosmetic mixture [53].

In addition to the toxic effects of TiO₂ NPs, discussed in previous chapters, these NPs have been also shown to promote photosynthesis and nitrogen metabolism, resulting in the enhanced growth of spinach. It increases the absorption of light and accelerates the transfer and transformation of the light energy. It was also found that treatment with nano-sized TiO₂ significantly increased the level of antioxidant enzymes, and decreased the ROS accumulation and malonyldialdehyde content in spinach chloroplasts under visible and UV irradiation. TiO₂ NPs also increased the superoxide dismutase activity of germinating soybean, enhanced its antioxidant ability, and promoted seed germination and seedling growth.

When E171 is part of a food product, it passes through the digestive system without causing harm because E171 combines with the other ingredients.