The need to review low-dose decision-making in radiation protection

The current approach in the system of protection, and the way in which it is implemented in regulation and practical application, has resulted in the allocation of significant and disproportionate societal resources to reduce relatively low-level exposures to even lower levels. The resulting exposure levels are often a fraction of the basic natural background level, and in particular are comparable to, or often significantly less than, the variability of natural background exposures due to individual decision-making, which the system of protection deems acceptable. There are arguments for a wider approach to decision-making at such low doses, recognising the uncertainties in radiation risk estimation and acknowledging the context that all human life takes place in a variable natural background radiation which generally dominates these lower dose exposures. Recommendations are presented for improvements in how decisions are made in controlling low doses.


Introduction-the basic issue
The current approach to radiation protection, including the system of protection itself and the way in which it is implemented in regulation and practical application, has resulted in the allocation of significant and disproportionate societal resources (including physical and financial resource) to reduce relatively low-level exposures to even lower levels. The resulting exposure levels are often a fraction of the basic natural background level (which can be taken as 2-4 mSv y −1 : i.e. a typical exposure for individuals in different counties worldwide, excluding the higher levels present to some extent in almost all countries), and in particular are comparable to, or often significantly less than, the variability of natural background exposures due to individual decision-making, which the system of protection deems acceptable.
This outcome is at variance with a common-sense approach to the way general society lives in a radiation environment, and has the potential to bring our profession into disrepute through poor utilisation of the common resources of society. In addition, the outcome is inconsistent with the widely accepted position that controls should be commensurate with the risk (HSE 2001).

Illustrative examples
2.1. Microsievert decisions: comparison of exposure from a holiday versus the clearance system Cornwall is an extremely popular UK holiday destination: it is also a relatively high radon exposure area, with average annual doses around 6 mSv y −1 higher than for the UK as a whole (PHE 2010). A typical two-week holiday might thus result in an additional exposure of up to around 200 µSv, being received by tens of thousands of persons each year. Holidaymakers are usually totally unaware of this additional radiation exposure.
The radiological practice of clearance, whereby very low-level radioactive material can be removed from regulatory control on the basis that the resulting exposure is regarded as trivial, is in theory aligned with an exposure of 10 µSv y −1 to the most exposed individual. In practice, because of many conservatisms in the system, the actual maximum exposure is around a hundred times lower-typically around 0.1 µSv y −1 (Coates 2016). The resulting very low level of allowed activity concentration in cleared material places additional costs on society of many £100 Ms-a figure derived for the UK alone (PHE 2018). It is extremely challenging to explain to individual members of the public, who have little understanding of the system of protection and radiation risk in general, why they should be paying such costs to save fractions of a µSv to a few individuals when it is perfectly acceptable under our radiation protection (RP) system for tens of thousands of persons to receive exposures 1000 times higher through an uninformed personal decision regarding holiday choice.

NORM and over-conservatism
The presence of naturally occurring radioactive material (NORM) in many substances has received considerable attention in recent years in international and regulatory organisations. This is despite the fact that the majority of doses from activities with NORM are comparable with the variations that exist in natural background doses.
Significant societal resources have been directed to managing and, in many cases, eliminating the low doses from NORM, rather than being used more effectively for broader safety and environmental improvements. This over-conservatism once again results from the lack of common sense in decision making structures in the low dose area. For NORM, the decisions on controls are driven by single minded compliance with conservatively developed administrative activity concentration levels rather than acceptable impacts to people and the environment.
While the international organisations that develop the administrative controls advocate a sensible approach to their application (for example through a graded approach), in practice too often the control levels are seen as the boundary between a safe and unsafe level.

Reasonableness in optimisation
Judgements on what is 'reasonable' are at the heart of optimisation of exposure-As Low As Reasonably Achievable (ALARA). Whilst optimisation has generally been a success story, there is concern amongst practitioners that in some situations there are pressures to move from individual judgement based on reasonableness towards an approach which is minimisation of exposure (Coates and Czarwinski 2018). This inevitably results in the unfortunate and unnecessary utilisation of additional societal resources. This issue is further explored in a recent International Radiation Protection Association (IRPA) Perspective paper (IRPA 2021).

Natural background exposure
The range of possible natural background exposures around the world is very large but in this paper we consider only the basic inescapable minimum exposure, which is typically 2-4 mSv y −1 . It is accepted that the majority of such exposure is uncontrollable, but this is not totally the case in regard to exposures resulting from individual decision-making.
Decisions impacting radiation exposure made on a day-to-day basis by individuals include such things as: • Where/whether to go on holiday • How to travel (e.g. flying) • What to eat (e.g. seafood) • Whether to change house The combined impact of such decisions can typically add a 'Delta' to a person's individual exposure of a very significant fraction of a mSv y −1 . These lifestyle decisions are usually made without any personal knowledge of resulting radiation exposure. Such exposure is often referred to in RP terms as uncontrollable exposures as a part of the existing exposure situation. However, in theory they are indeed controllable, as evidenced below: • UK laws exist regarding the safety of rented accommodation, for example for the standard of gas and electricity installation. Radon standards could similarly be applied. • The risk from radiation exposure due to flying could at least be brought to the attention of passengers through safety warnings, as per legal requirements for labelling on cigarette packets • Food safety laws exist, and could be applied to food with higher activity concentrations.
• Laws exist relating to the sale of property with potential safety hazards.
The point here is not to advocate the above steps, which would clearly be disproportionate at the levels of dose under consideration here, but to emphasise the argument that these activities are not 'uncontrollable' . In fact our system of protection has made a decision on behalf of the public that it is not appropriate to control these activities and there is no need to directly inform the public of any associated potential risk. These types of exposure-the 'Delta'-are deemed acceptable through the implementation of the RP system in national regulations.
It is somewhat incongruous that whilst it is accepted as being clearly disproportionate to control some exposures at the level of a significant fraction of a mSv, the currently-accepted radiation protection approach leads to the imposition of significant restrictions on other much lower exposures, placing a significant and unnecessary burden on society.

Discussion
It is very challenging to explain to typical members of the public why we should allocate significant societal resources to ensuring extremely low doses in some cases, whilst at the same time formally allowing much higher exposures from individual decision-making, usually without those directly involved having relevant knowledge. This has the potential to lead to a lack of confidence in our profession, and more importantly leads to an unnecessary cost burden to society. It goes against what is widely regarded as 'common sense' , a value that our system of protection would appear to have neglected.
The exposures under consideration in this discussion are usually quite small fractions of relevant dose limits or reference levels, and as such are compliant with the RP principle of limitation. It is agreed that the principle of justification must be applied to all exposure situations-an exposure situation cannot be deemed as 'justified' purely on the basis that exposures are small in comparison to natural background. The arguments in this discussion therefore relate to determining the optimised level of protection.
The concept of tolerability of risk has been used to underpin the system of protection. The classical approach (e.g. HSE 2001) has been to compare radiation risk with wider risk situations generally accepted in society. Under this approach perhaps more recognition should be given to the uncertainty in risk from radiation at very low doses, where all we really know is that if there is a risk it is what would generally be regarded as very low (and which must have an upper bound due to the lack of detectability of risks from natural background exposure). Whilst an element of prudence is appropriate, it should be kept in mind that there are imbalances in comparing real known deaths, for example from industrial accidents and road fatalities, with inferred hypothetical risks from radiation which can only be postulated through extrapolation from risks at higher exposure levels. Additionally, there needs to be caution in comparing radiation detriment, a complex quantity with few comparators in other risk types, with recorded deaths from other hazards.
This classical approach to tolerability of risk gives one perspective on what may be judged as acceptable. However, in the specific case of radiation it is also appropriate to take account of the context of natural background exposure and its variability, as discussed above. The universal existence of such background exposure gives a different dimension to radiation risk which is not common in other risk situations, and allows a more 'common sense' approach to be taken into account when judging what may be tolerable.
It is very well accepted in our profession that public engagement and understanding is central in our decision-making. It is also widely recognised that the way in which people perceive different types of risks varies with the nature of the risks-some are considered to be more acceptable/tolerable than others. For example, natural background exposures may be considered to be more acceptable than some types of imposed exposure, and this is a consideration which should be taken into account amongst all the factors in low-dose decision-making. Whilst perception issues are indeed relevant, in the author's opinion they cannot account on their own for the imbalances discussed in section 2 above.
It is therefore particularly important in our public communication and engagement to give greater focus to the context of the universal natural background exposure and how this links with our daily lives. Whilst public acceptance is a relevant issue, it needs a rounded consideration acknowledging this wider context as well as the conventional approach of balancing risks and benefits. The tendency in some authorities to move to requiring very low doses as a response to perceived public concern is wasteful of resources and does not help. Indeed, it only serves to fuel radiation phobia-'if it needs to be that low, this kind of radiation must be really dangerous' .

Conclusions and recommendations
The overall objective of this discussion paper is to bring the radiation protection system into better alignment with how the 'common sense' approach of the public views risks, especially in a widespread radiation environment. Further consideration should be given to how best to balance all the factors relevant to decision-making at these low doses around the mSv level, including considerations of tolerability, public perception, avoidance of radiation phobia, the context of natural background radiation and its variability, together with the need to ensure value in the use of society's resources. A broader approach to decision-making at low dose would result in a more rational, realistic and relateable approach, with less emphasis on the need to pursue ever lower doses.
The following recommendations are made.
(a) Give greater emphasis to our 'universal radiation world' of natural background exposure, both in general decision-making and in our interactions with the public. (b) Review the approach to tolerability of risk which underpins the system of protection, taking account of broader inputs to this concept, including the scale and variability of normal background radiation exposure and the way this is considered by the public. (c) Further reinforce the concept of optimisation, emphasising that this is not minimisation of exposure and that appropriate consideration should be given to ensuring a balanced use of societal resources. (d) Continue the emphasis on public engagement on radiation and risk, but avoid the temptation to address 'perceived public concern' by pushing for unnecessarily low exposures. (e) Ensure that decisions at low doses are based on realistic dose estimates rather than overly-conservative assessments.