Nanoparticle toxicology works toward establishing the hazard of nanoparticles, and therefore their potential risk, in light of the increased use of exposure. The current study was research proper characterization of the nanoparticles for understanding of their toxic effects and mechanisms at the cellular level. Dose and time as a main parameters is essential in hazard identification and risk assessment of nanomaterials. Material for the evaluation of toxic effects was used 20 samples of commercially available and laboratory preparations of metals and nanocarbon, divided into main groups: carbon nanoparticles, metal oxide nanoparticles and metal nanoparticles in different concentration. Fresh water infusoria stylonychia mytilus (wild strain) in exponential growth phase was used as the test object. Analysis of data on oxides of the metals showed higher toxicity than metal nanoparticles. In groups the maximum toxicity was observed in iron oxides (Fe3O4, Fe2O3), copper (CuO) and molybdenum (MoO3) (0,1; 0,025; 0,0125 М) after 24 hours of incubation with the test object Analysis of the effect of metal nanoparticles on the cells of infusoria showed that the maximum toxic effect was observed when exposed to Cu, Fe, Ag (0,025-0,0015625 М). Statistical analyses showed a high correlation between concentration and time (P≤0,001). The issue of accessibility of nanomaterials released in the environment for living organisms has been poorly studied. The toxic effects of nanoparticles can be associated with their size and their physicochemical properties.