The first scientific opinion on the safety of titanium dioxide as a UV-filter at a maximum concentration of 25 per cent in cosmetic products was adopted on the 24th of October 2000 by the SCCNFP (SCCNFP/0005/98).
Now, according to the Committee, a review of the substance in its nanoform is deemed necessary as; “The SCCNFP opinion from 2000 (SCCNFP/0005/98) is on micro-crystalline preparations of TiO2 and preparations of coarse particles. Since this opinion, new scientific data on nanosized particles including, TiO2 has become available.”
The review comes as the SCCS reports the risk assessment of nanomaterials to be consistently evolving and in particular, the toxicokinetics aspects to have not yet been fully explored in the context of nanoparticles (e.g. the size dependency). Also, long term stability of the coatings remains unclear.
In this instance the SCCS considered if the use of titanium dioxide in its currently approved concentration is safe at 25 per cent as a UV-filter in sunscreens, of which it reconfirmed but noted that the overviewed concentration did not apply to applications that might lead to inhalation exposure to TiO2 nanoparticles (such as powders or sprayable products).
It is also worth highlighting again that 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 used in a sunscreen formulation can penetrate skin (healthy, compromised, or damaged skin) to reach viable cells, then the SCCS may consider revising this assessment.
In regards to the opinion of Zinc oxide, adopted on the 18 September 2012 (SCCS/1489/12), the SCCS also considered that the use of nano forms and non-nano forms of ZnO at concentrations of up to 25 per cent are safe.
"In summary, it is concluded on the basis of available evidence that the use of ZnO nanoparticles with the characteristics as indicated below, at a concentration up to 25 per cent as a UV-filter in sunscreens, can be considered not to pose a risk of adverse effects in humans after dermal application."
This does not apply however, to other applications that might lead to inhalation exposure to ZnO nanoparticles (such as sprayable products). For a more detailed rundown of what is and isn't included please see here.