Is one of the most effective and safe UV filters also safe in its nano form?
Titanium dioxide (TiO2) is a white pigment, for example used in white paint (similar to Zinc Oxide, ZnO), that is used as UV filter. It has a stronger protection against UVB, and therefore sunburn, than ZnO but does not cover quite as broadly against UVA radiation. Similar to ZnO, TiO2 particles can leave white streaks on the skin when used in sunscreen. This problem can be solved by using TiO2 in its nano form.
Does SCCS consider titanium dioxide in its nanoform as an UV-filter safe for the consumers?
TiO2 does to not pose any risk of adverse effects in humans after application on healthy, intact or sunburnt skin. However, this opinion is based on the currently available scientific evidence which shows an overall lack of dermal absorption of TiO2 nanoparticles. If any new evidence emerges in the future to show that the TiO2 nanoparticles can penetrate skin the SCCS may consider revising this assessment.
However, breathing in nanoparticles can be toxic and lead to lung inflammation. Some tests suggest that this could also lead to cancer. The European Scientific Council for Consumer Safety advises not to use TiO2 nanoparticles in powders or sprayable products. There is also a very low risk for skin or eye irritation and skin sensitization. There is not sufficient information on reproductive toxicity, but some scientific evidence suggests that TiO2 nanomaterials, if they penetrate the skin, can cause damage to genetic material. However, such effects are unlikely when used in a cream.
Generally, Titanium Dioxide is considered one of the safest options for the environment and is also used in so-called reef-safe sunscreen. However, one recent study found that TiO2 (nano) harms plankton when it interacts with UV radiation.
In conclusion, nanoparticles of Titanium Dioxide are generally safe to use and a good choice for sunscreen. Reports that TiO2 is carcinogenic are true (both as nano and micro particles) but the general consensus that this is only an issue when inhaled. However, the interactions of TiO2 nanoparticles with aquatic life are still unclear and under investigation.