Prudence and the Hidden Burden of Conservatism

The ethical value of prudence is deeply, and rightly, embedded within our system of protection. Definitions of prudence include such concepts as: a sensible and careful attitude in making judgements and decisions: behavior that avoids unnecessary risks: care, caution and good judgement, looking ahead: making informed and carefully considered choices. These are all concepts with which, at the level of principle, one cannot disagree - but these concepts are also judgmental. What may be prudent behavior at one level of risk may well not be the best approach at a much lower risk level. However, in radiation protection we seem to have lost a sense of proportionality, and we tend to apply the same level of precaution whatever the level of exposure.
In our training for the profession of radiation protection the concept of prudence has had a very strong influence on our mindset. As practitioners we have unthinkingly drifted into an assumed need for significant levels of conservatism in our day to day work, whether it be assessments, safety cases or operational judgements, without sitting back to assess either (a) the impact of this on our activities or (b) how much conservatism is actually appropriate to any given situation. In practice of course this results in actual exposures being much lower than intended, expected or indeed, necessary. In many cases this occurs without any realization or recognition of the reality, and leads to potentially significant imbalances within the system of protection.
This is exacerbated by the fact that, in almost all situations, assessments of exposure and related operational processes rely on multiple factors and parameters, each of which is usually chosen ‘conservatively’, with the conservatisms multiplying together. Hence the degree of conservatism in the overall outcome is often very significant, and usually unknown and hidden from consciousness.
As an example, a study of the conservatisms in the clearance process has been undertaken. The agreed international basic philosophy on the clearance of materials from regulatory control is based on an acceptance that resulting doses should not exceed ‘some tens of µSv/y’. In practice, due to multiple conservatisms within the total clearance regime, the actual doses received do not exceed a few tenths of µSv/y, and are indeed likely to be even lower still. This is at least two orders of magnitude below the top tier criterion, which was itself set on very prudent considerations.
How have we got into this situation? There are many subtle contributions, some of which are outlined as follows.
The need for a conservative approach is underpinned by international guidance on assessments. On close examination the context often relates to assessments which are aiming to demonstrate compliance with fixed numerical limits, but in practice the guidance has become a normal part of the assessment regime for any assessment - at any dose level, for any purpose. This approach is often reinforced by regulatory expectations.
Our current approach as RP practitioners has been founded on many years of experience. Much of this experience and practice has developed over periods where both occupational and public exposures were much higher than current levels, and hence where it could be argued that higher levels of conservatism may have been appropriate. We have not re-adjusted our sights to a new reality where by far the majority of exposures that we are aiming to control are well below any relevant limits, and indeed are adding only marginally to natural background exposures.
What are the consequences of an overly-conservative approach? Firstly, we are not giving due consideration to another key ethical value within our system of protection – that of beneficence, which at its broadest relates to ‘doing the best that can be done with society’s resources’. Every sum of money we spend on reducing radiation exposures to unintended or unwarranted low levels is an opportunity cost for society – the resource cannot be spent elsewhere, where it could potentially give better benefits to society.
The second obvious outcome is that this has contributed to the ‘ever lower doses’ trend that is evident across much of our RP world. We need to look more consciously at what the term ‘reasonable’ means in ALARA.
As a profession we are at a cross-roads. We need to review our practices to ensure that we do not head in the wrong direction, which would result in significant costs to society with no real return or benefit.