Is there actually a specific nanorisk?

Could the "nano" risk be limited to a set of identified dangers: irritating, corrosive, toxic, inflammable, or dangerous for the environment for example? What are the reasons for giving specific attention to this risk?

Some say that for many years chemists have been doing nanotechnology without knowing it. But we must distinguish between two categories of risks:

• known risks, including explosion risks related to the Explosive Atmosphere (ATEX: 1999/92CE and 94/9CE directives) or the classic toxicity of a chemical in the macroscopic form,
• potential or supposed risks, specifically related to the size and surface reactivity of the particles, as their shape facilitates cell penetration or their ability to fix and carry pollutants in the ecosystem.