Québec is very active in research in the field of nanoparticle development and nanotechnology. More than 35 production companies already exist or are in the start-up phase. It is believed that the number of Québec workers potentially exposed will grow over the next few years. To prevent the development of occupational diseases or the occurrence of accidents, the IRSST began a review of world-wide scientific knowledge to evaluate whether there are known risks associated with this emerging sector. An initial report addressing the health effects (R-451) shows that a limited number of toxicological studies exist, but all of these studies conclude that there are some health risks following exposure to nanoparticles. Although numerous risks are associated with the nature of nanoparticles, it has now been clearly established that toxicity is related to the surface area of these particles and not their mass, and that, for a given substance, the toxicity is much higher when it is of nanometric size than micrometric size. - The second report (R-455) summarizes current knowledge about nanoparticles, their synthesis and applications, health and safety risks, and the challenges in evaluating occupational exposure. Also discussed are nanoparticle-related occupational health and safety control and prevention aspects.