Nano is a big buzzword in beauty, especially in sunscreens where this emerging technology has allowed scientists to break down ingredients—like zinc or titanium dioxide—into tiny particles. Problem is, these nanoparticles are so small that they can penetrate cell walls, including organ tissues. Researchers found that inhalation of carbon nanotubes led to mesothelioma—the same kind of cancer linked to asbestos. While the EPA continues to assess the potential dangers of nanotechnology, stay away from nanomaterials in cosmetics, especially sunscreens.