Reasonableness and Tolerability in the System of Radiological Protection: ICRP on-going reflections.


IAEA - International Conference on Radiation Safety: Improving Radiation Protection in Practice, 10 November 2020.


The model of reasonableness and tolerability of radiological risk is a conceptual framework for the implementation of the ICRP principles of optimisation (guided by constraints and reference levels) and limitation, based mainly on the level of exposure, and closely related to the level of risk. Discussions of reasonableness and tolerability have been part of ICRP publications for many years, including the introduction of a model of risk tolerability in Publication 60 (1990). More recently, Publication 101 (2004) developed the approach to address the implementation of the optimisation process and the way to elucidate what is reasonably achievable. Further considerations have been addressed while examining the ethic, identifying four core values underpinning the system of radiological protection. In 2019, ICRP has set up a dedicated task group to review the historical and current perspectives on reasonableness and tolerability in order to consolidate and clarify Publication 103, and to prepare the considerations and basis needed for development of future recommendations.

This model provides guidance for the implementation of the principles in planned, emergency and existing exposure situations. Reasonableness plays a key role in the decisions regarding appropriate levels of protection and is the core of the implementation of the optimisation principle taking into account societal and economic aspects, and also protection of the natural environment. Reasonableness applies to any exposure situation as far as an optimisation process is implemented, although what may be considered reasonable will depend on the specifics of the situation and involvement of stakeholders in an inclusive process. 

The ICRP on-going reflections on reasonableness and tolerability in the system of radiological protection have already identified a wide number of questions to be addressed, including, for example: What is the link between tolerable and reasonable? Tolerable and reasonable for whom? What are the considerations and criteria on which the concepts of tolerability and reasonableness are based? What is the trade-off between level of exposure and benefit? How do we account for sensitive or vulnerable populations? How are interests reflected and integrated for human and nonhuman exposure?  How do we best support reasonable value for society? What are some strategies to assist in balancing competing values in determining what is tolerable and/or reasonable? Are the same criteria applicable for tolerability in all exposure situations?  How do different paradigms used for non-radiological risks inform and contribute to radiological protection?

For addressing these questions, the model of reasonableness and tolerability of radiological risk is revisited with the following objectives:

  • Better articulate the link between tolerability and reasonableness in the process of implementation the radiological protection system, with clarification on the criteria to be considered for defining “where we don’t want to go above” and which process could be put in place for evaluating “what is reasonable”.
  • Refine the criteria to be considered and their link with dose limits and reference levels, relying on the radiological detriment as benchmark for tolerability and reasonableness as well as using risk comparison but without limiting to numerical criteria.
  • Emphasize the importance of the application of the model for the different exposure situations, including the deliberative process with the stakeholders for the implementation of the optimisation principle, referring to good judgement, fairness, practicability and moderateness.

This paper will present the current reflections of the ICRP Task Group with the aim to get feedback from the participants and national and international organisations on their views on these issues.


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