Nanotechnology, cosmetics and the…there a health risk?

Insoluble nanoparticles like TiO2 and ZnO (common in sunscreens) don't penetrate living human skin. Toxicity tests found these nanoparticles are non-toxic, with no safety difference between nano and micro-sized versions. The evidence suggests nanoparticles in cosmetics pose no health risk, while their use in sunscreen provides major benefits like skin cancer protection.