There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO 2 or amorphous SiO 2 nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO 2 and TiO 2 nanoparticles can be hazardous. Thus, in the design of nanocomposites with such nanoparticles, hazard reduction extending to the full nanocomposite life cycle would seem a matter to consider. Options for hazard reduction include: changes of nanoparticle surface, structure or composition, better fixation of nanoparticles in nanocomposites, including persistent suppression of oxidative damage to polymers by nanoparticles, and design changes leading to the release of relatively large particles.