For an equivalent mass dose, the nanoparticle total surface is inversely proportional to its size. The chemistry reactivity particle is linked to the surface. A particle size rise causes an increase of their biological and chemical reactivity (interaction with different tissues, cells and biological fluids of the organism, protein denaturation,…).

Some particles have the property of absorbing at their surface substances present in the environment, substances which have the possibility to reach various organs and lead to specific toxic effects.