With the advent of nanotechnologies, potential health hazards of nanoparticles have raised great concern. To prevent the potential hazards of new materials, health risk management of nanotechnologies is necessary. Health risk assessment is the basis of risk management. Currently, nanotoxicologists agree that it is the free nanomaterials that may cause health hazards, and the factors associated with hazards are its size, surface area, coating and shape. However, the toxicity studies of nanoparticles are limited on few materials. Studies have shown that nanoparticles can cause lung inflammation and fibrosis, and thrombosis in diseased animals. The dose-response relationship for nanoparticles is not clear. However, it is noted that diseased animals are more susceptible to nanoparticle exposure. Nanoparticles may enter human bodies through inhalation, ingestion and skin penetration. Because of the lack of portable measurement instruments, the data on exposure assessment remain limited. Thus, based on our current knowledge, it is not possible to draw a conclusion on risk characterization on nanoparticles. Further, we review the risk analysis reports from the United Kingdom and the European Commission. In order to manage the risk of nanotechnologies, they suggest launching an incremental process using existing legislative structures.