1. Damocles. Risk sources that have a very high potential for damage but a very low probability of occurrence.
2. Cyclops. Events where the probability of occurrence is largely uncertain, but the maximum damage can be estimated
4. Pandora. Characterised by both uncertainty in probability of occurrence and the extent of damage, and high persistency
e.g. organic pollutants and endocrine disruptors.
5. Cassandra. Paradoxical in that probability of occurrence and extent of damage are known, but there is no imminent societal concern because damage will only occur in the future. There is a high degree of delay between the initial event and the impact of the damage. e.g. anthropogenic climate change.
6. Medusa. Low probability and low damage events, which due to specific characteristics nonetheless cause considerable concern for people. Often a large number of people are affected by these risks, but harmful results cannot be proven scientifically. e.g. mobile phone usage and electromagnetic fields.
3. Pythia. Highly uncertain risks, where the probability of occurrence, the extent of damage and the way in which the damage manifests itself is unknown due to high complexity. e.g. human interventions in ecosystems and the greenhouse effect.
Each of these risk classes is indicative of a different configuration of what Renn cites as the main challenges in risk management: complexity, uncertainty and ambiguity. Renn contends that the inclusion of such variables in a risk prioritisation system would enable us to deal with risks more realistically, effectively and in a targeted way, and in doing so would ultimately lead to more rational risk policymaking.
Renn, O. (2008) Risk Governance: Coping with Uncertainty in a Complex World. London: Earthscan.
https://www.taylorfrancis.com/books/risk-governance-ortwin-renn/10.4324/9781849772440
