Table 4 Overview on possible classifications for considering ENM in major accident regulations

1

All ENM have the same (eco)toxicity as larger particles with the same composition. Some specific ENM are placed in the exemption list

Simple rule; recognizes the higher risk potential of certain ENM

Insufficient data to select exemptions

2

Each manufacturer has to provide specific (eco)toxicological tests for each ENM, independent of the chemical composition of the ENM

The nano-aspect as well as the different properties of various ENM are considered

Problem of definition of ENM; expensive for companies that produce only small amounts or small variations of materials

3

Dispersions are classified like normal chemicals; for powders, a nano-specific regulation is implemented in addition to existing regulations for powders

The different risk of dispersions and powders is accommodated. Simple to define

Possible exemptions need to be formulated (see 1)

4

For ENM in powder form, the mass threshold is reduced by a factor of 10 to accommodate the higher surface area

The precautionary principle and the increased surface area of the nanoparticles are considered

Relatively unspecific

5

ENM are categorized (e.g., soluble/insoluble, metal oxides/metals/organic ENM) and assessed differently

Differences between particle types are considered

Material-specific properties are over-represented; many exemptions