Prudence

To make informed and carefully considered choices without the full knowledge of the scope and consequences of an action.

ICRP Publication 138, 2018

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One of the four Core Ethical Values underpinning the System of Radiological Protection described in ICRP Publication 138:

• Beneficence and non-maleficence
• Prudence
• Justice
• Dignity

Excerpt from ICRP Publication 138 Ethical Foundations of the System of Radiological Protection

3.2. Prudence

(42) Prudence is the ability to make informed and carefully considered choices without full knowledge of the scope and consequences of actions. It is also the ability to choose and act on what is in our power to do and not to do.

(43) Prudence has a long history in ethics. It is considered to be one of the main virtues rooted in the Western tradition developed by Plato and Aristotle; the teaching of Confucius; the Hindu and Buddhist philosophies; and the ancient traditions of the peoples of Eurasia, Oceania, and America. Originally, prudence signifies ‘practical wisdom’, which is the meaning of the Greek word ‘phronesis’. It describes the quality of having knowledge, experience, and good judgement to take reasonable decisions and to act accordingly.

(44) The system of radiological protection is based on solid scientific evidence; however, there are remaining uncertainties at low levels of exposure that necessitate value judgements. Decision making requires prudence as a central value. However, prudence should not be taken to be synonymous with conservatism or never taking risks. It describes the way in which decisions are made, and not solely the outcome of those decisions.

(45) It is worth noting that prudence appeared in the late 1950s (ICRP Publication 1) in the Commission’s recommendations in relation to the uncertainties related to stochastic effects. Since then, it has been constantly re-affirmed in relation to the linear no-threshold (LNT) model. Thus, in ICRP Publication 103, one can read: ‘The LNT model is not universally accepted as biological truth, but rather, because we do not actually know what level of risk is associated with very-low-dose exposure, it is considered to be a prudent judgement for public policy aimed at avoiding unnecessary risk from exposure’.

(46) More specifically, the term ‘prudence’ is used explicitly in connection with the different types of effects of radiation exposure considered in the system.

• Deterministic effects: ‘It is prudent to take uncertainties in the current estimates of thresholds for deterministic effects into account . . . Consequently, annual doses rising towards 100 mSv will almost always justify the introduction of protective actions’ (ICRP Publication 103).

• Stochastic effects in general: ‘At radiation doses below around 100 mSv in a year, the increase in the incidence of stochastic effects is assumed by the Commission to occur with a small probability and in proportion to the increase in radiation dose . . . The Commission considers that the LNT model remains a prudent basis for radiological protection at low doses and low dose rate’ (ICRP Publication 103).

• For heritable effects in particular: ‘There continues to be no direct evidence that exposure of parents to radiation leads to excess heritable disease in offspring. However, the Commission judges that there is compelling evidence that radiation causes heritable effects in experimental animals. Therefore, the Commission prudently continues to include the risk of heritable effects in its system of radiological protection’ (ICRP Publication 103).

(47) Policy makers do not generally refer to prudence. Instead, reference is made to the precautionary principle, which was popularised by the Rio Conference on Environment and Development (UNCED, 1992). This principle, which states that lack of scientific certainty shall not be used to justify postponing appropriate measures ‘where there are threats of serious or irreversible damage’, has been much debated in connection with the ethics of decision making in recent years. This is also at stake in the domain of radiological protection (Streffer et al., 2004).

(48) Neither prudence nor the precautionary principle should be interpreted as demanding zero risk, choosing the least risky option, or requiring action just for the sake of action. The experience of over half a century of radiological risk management applying the optimisation principle can be considered as a reasoned and pragmatic application of prudence and/or the precautionary principle. Interestingly, the Commission mentions in its most recent recommendations that the use of the LNT model remains a prudent basis for radiological protection at low doses and low dose rates considered ‘to be the best practical approach to managing risk from radiation exposure and commensurate with the ‘‘precautionary principle’’’ (UNESCO, 2005; ICRP Publication 103).

(49) The implications of this prudent attitude have been significant for the subsequent structuring of the system of radiological protection. A careful study of the evolution of the Commission’s recommendations over the past decades shows that this central assumption led to gradually shaping the system as it stands now (Lochard and Schieber, 2000). This is clearly summarised by the Commission as follows: ‘The major policy implication of the LNT model is that some finite risk, however small, must be assumed and a level of protection established based on what is deemed acceptable. This leads to the Commission’s system of protection with its three fundamental principles of protection’ (ICRP Publication 103).

(50) In addition, the adoption of a prudent attitude induces the duty of vigilance vis-a` -vis the effects of radiation, resulting in an obligation to monitor radiological conditions for humans and non-human biota. Specifically, prudence requires that research should be open to unexpected findings, beyond the obligation to conduct relevant research in an attempt to reduce existing uncertainties (e.g. epidemiology, radiobiology, metrology, radio-ecology). Furthermore, for humans, prudence implies support of the exposed population, including – if necessary – detection and treatment of possible pathologies induced by ionising radiation.