Activation of oxidative stress-responsive transcription factors cause inflamation which is important because chronic inflammation and oxidative stress may cause a number of particle-specific effects such as fibrosis, genotoxicity and cancer caused by fibres or secondary mutation. Apart from toxicity, genotoxicity and carcinogenicity are one of the posible adverse effects of nanopaticles which draws the most attention. ZnO nanoparticles have a genotoxic potential in human epidermal cells even if bulk ZnO is non-toxic, which suggests the impact of particles’ diameter. Carcinogenic effects of persistent particles such as asbestos have been suggested to be due to the local generation of granulomas and fibrosis in the lungs. Also lung tumors have been reported following chronic inhalation of very high doses (10 mg/m3 ) of nano-TiO2