mathematically from the assumption that people are exposed to roughly 20 types of technological systems. Among these are technologies of transport, energy production, chemical industries, and leisure activities. Assuming that a total technological risk in the size of the MEM is acceptable, the contribution from each system is confined to
(5.3)
A single technological system thus poses an unacceptable risk if it causes the individual risk to be increased by more than 5% of MEM. It should be emphasized that this criterion concerns the risk to any individual, not only the age group that provides the reference value. Unlike ALARP and GAMAB, MEM offers a universal quantitative risk acceptance criterion that is derived from the MEM rate.
The MEM principle primarily relies on the technology principle as its basis, in that the criterion is related to existing risk levels.
5.3.5 Societal Risk Criteria
In 2001, the UK HSE published the report “Reducing Risks, Protecting People” (HSE 2001), which includes a proposed societal risk criterion which says that for any single industrial installation, “the risk of an accident causing the death of 50 or more people in a single event should be regarded as intolerable if the frequency is estimated to be more than one in five thousand per annum.” This was the first time there had been a widely consulted and published criterion of this type.
5.3.6 The Precautionary Principle
The precautionary principle differs from the other approaches described in this chapter. Common for these approaches is that they are risk‐based, which means that risk management is to rely on the numerical assessment of probabilities and potential harms (Klinke and Renn 2002). The precautionary principle is, in contrast, a precaution‐based strategy for handling uncertain or highly vulnerable situations. The precaution‐based approach does not provide any quantitative criterion to which the assessed risk level can be compared. Risk acceptability is instead a matter of proportionality between the severity of potential consequences and the measures that are taken in precaution.
The original definition of the precautionary principle is given in principle 15 of the UN declaration from Rio in 1992 (UN 1992):
Definition 5.4 (Precautionary principle)
Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost‐effective measures to prevent environmental degradation.
The precautionary principle is invoked where
There is good reason to believe that harmful effects may occur to human, animal, or plant health, or the environment.
The level of scientific uncertainty about the consequences or frequencies is such that risk cannot be assessed with sufficient confidence to inform decision‐making.
Invocation of the precautionary principle may be appropriate with respect to, for example, genetically modified plants where there is good reason to believe that the modifications could lead to harmful effects on existing habitats, and there is a lack of knowledge about the relationship between the hazard and the consequences. A contrary example is that of the offshore industries, for which the hazards and consequences are generally well understood and conventional assessment techniques can be used to evaluate the risk by following a cautionary approach. Invocation of the precautionary principle is therefore unlikely to be appropriate offshore.
The European Commission has provided guidance on when and how to use the precautionary principle (EU 2000). Studies have shown that the practical implementation still varies significantly (Garnett and Parsons 2017). The decision when to invoke the principle seems to be poorly defined, and there are indications that less evidence is required if the issue is related to harm to people compared to the environment.
Example 5.4 (Deliberate release into the environment of GMOs)
EU Directive 2001/18/EC (EU 2001) is concerned with the deliberate release of genetically modified organisms (GMOs) into the environment. The directive states that risk related to release of GMOs need to be controlled, both related to people and ecosystems. It is therefore necessary to take preventive actions. The precautionary principle has been followed in the preparation of the directive and it should also be taken into account in its implementation. Further, “No GMOs [
5.4 Risk Acceptance Criteria for Other Assets than Humans
The discussion above is primarily concerned with risk to humans. For other types of assets, other considerations may apply. Brief comments are given on the two most important, environment and economic risk.
Environmental RACs are based on the principles discussed earlier in this chapter. The ALARP principle is commonly applied and the precautionary principle was originally developed specifically for environmental applications. The underlying principles of the ALARP principle can be applied to environmental consequences, although the term “environment” covers an extremely wide range of vulnerable assets, from natural beauty, to individual species (being it animals, insects, fish, plants, etc.), to complete ecosystems. Comparing these and assessing the risk on a consistent level is clearly challenging.
Economic considerations are usually simple, and risk acceptance can in most cases be based solely on cost–benefit analysis. The option with the highest benefit is normally the preferred option. In some cases, consideration of worst‐case consequences may be necessary. This is because the consequences in some cases may be catastrophic, in the sense that a company goes bankrupt if certain events occur. In such circumstances, this may override a criterion based purely on costs and benefits.
5.5 Closure
There has been an ongoing discussion in the scientific community regarding the adequacy of RAC for making decisions about risk. Among the critics is Terje Aven (e.g. see Aven 2007 ; Aven and Vinnem 2005), who questions the use of RAC from a decision theoretical and ethical perspective. Risk acceptability evaluations must be based on ALARP‐considerations, he claims, and not static criteria that fail to address the relationships among risk, benefits, and improvement. In view of the fact that the benefits we gain from accepting a risk weigh so heavily, it may be reasonable to argue that we do not need a specific upper limit, but rely solely on weighing risk against benefits.
Johansen (2010) takes a more pragmatic perspective by suggesting that RAC should be evaluated according to their feasibility to the decision‐maker and the extent to which they promote sound decisions. The first issue is primarily a matter of how we measure risk, and the ability of different measures to rank alternatives and provide precise recommendations with little uncertainty. The second is a matter of how the criteria are derived
