Just like any other chemical substance, some nanomaterials are hazardous and others not. The nanoscale of the particles does not imply hazard as such. Instead the potential effects are based on the inherent toxicological properties and the quantity (dose) taken up by an organism (humans or an animal).

One of the main objectives in identifying a hazard is to establish the “dose-effect relationship”, based on toxicological studies. By doing so, a dose threshold can be determined where below this threshold it is assumed that no adverse effect will occur, and above, the potential risk needs to be controlled and managed through e.g. exposure mitigation.

Traditionally for chemicals, these dose thresholds are expressed as a mass concentration or number concentration (for fibres). Scientific research has showed that for nanoparticles, other units, for example their surface area may be a better way to describe toxicity where the dose threshold may be expressed in units of surface area.