Nanotoxicity factors.

The effects of a toxic substance on human health are based on the inherent toxicity and quantity (dose) of the product in contact with the organism. 

One of the main objectives of toxicological studies is to establish dose-effect relations, to determine dose thresholds below which no health effect is to be feared. 

Traditionally, these doses are expressed in mass or number (for fibers). In the case of nanoparticles, it appears that the surface area is an important parameter of toxicity, which could justify that the dose be expressed in units of surface.