The current system of radiological protection, that aims to avoid tissue reactions (deterministic effects) and minimize risk of stochastic effects (cancers and hereditary effects), through justification and optimisation of practices and limitation of exposures, is based on estimations of risk to a notional average person. The use of an age- and sex-averaged approach is not a reflection of the reality of population structures, but is a pragmatic approach. However, we know that there are variations in radiosensitivity between individuals within the population. The underlying reasons for this variation can be genetic (for example, the radiation-sensitive syndromes such as ataxia telangiectasia and Gorlin syndrome), epigenetic and also environmental or behavioural (for example, the difference in lung cancer risks in smokers and non-smokers). A better understanding of the factors that underlie inter-individual variation in response to radiation, and the magnitude of the variation could impact on the approaches adopted to radiation protection in the occupational, medical and public sectors. One example where this may impact is in radiotherapy for cancer, where severe normal tissue complications can be observed in a sub-set of the individuals treated. Understanding the subpopulations for which such severe complications occur, and the underlying mechanistic basis could inform radiotherapy treatment decision making, improving tumour cure rates while avoiding the severe complications. In 2018, the International Commission on Radiological Protection established a Task Group, TG111 to consider Factors Governing the Individual Response of Humans to Ionising Radiation. The aim of this presentation is to review the current state of knowledge on variation in individual response to radiation and to provide an update on progress with the work of the ICRP Task Group.
Keywords: radiation response; variation; inter-individual