Safety of nanoparticles in sunscreens

Sunscreens may contain ZnO or TiO2 nanoparticles to absorb UV radiation. Available data do not allow for precisely establishing risk associated with these nanoparticles. However, there is substantial evidence that the hazard of TiO2 and ZnO nanoparticles probably comes from their ability to generate reactive oxygen species (ROS) and to elicit inflammatory responses. In view of the precautionary principle, it may be argued that UV absorbing nanoparticles should be produced in such a way that the generation of ROS and inflammatory responses under real-life conditions are minimized as much as technically and commercially feasible.