HAZARD versus CLASSIFICATION, RISK versus EXEMPTION

It is widely agreed (see also GHS) that classification of dangerous goods is based on hazard, i.e on the intrinsic characteristics of the substance/mixture.

Risk analysis (i.e. definition of events, probability of events, magnitude of negative effects) is not playing (should not play) a role in classification.

But, moving to the development of criteria for specific requirements, such as the choice of specific limits for exemption from the (or some parts of the) regulations, (a sort of) risk analysis could be an useful tool.

Let us look to the existing values for the definition of:
- High Consequence Dangerous Goods in terms of security;
- Limited Quantities;
- Excepted Quantities:
- etc.

Where do the related figures come from ? What is the rationale ?
Should not be possible to develop a reference scenario
for deriving more sound values ?

I'm not thinking in terms of a complex risk analysis, but I'm looking for instance to the Q-system developed by IAEA (see Appendx I in Safety Guide TS-G-1.1, ST-2).

Could something similar be adopted also in the more general framework of the other dangerous goods ?