LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 1.3 Scientific uncertainties and vigilance Despite scientific advances in the fields of nuclear safety and radiation protection, many uncertainties persist; the French Authority for Nuclear Safety and Radiation Protection (ASNR) remains attentive to the results of scientific work in progress, in radiobiology and radiopathology for example, and on the possible consequences for radiation protection, particularly with regard to management of risks associated with low doses. These areas of uncertainty include individual radiosensitivity, agerelated effects, the existence of signatures (specific mutations of DNA) that could be observed in radiation-induced cancers and certain non-cancerous diseases observed after radiotherapy. 1.3.1 – The individual response to ionising radiation The effects of ionising radiation on human health vary from one individual to the next. The variability in individual radiosensitivity is observed at high doses of ionising radiation, notably in terms of tissue responses. It has been well documented by radiation oncologists and radiobiologists. Radiosensitivity at a given dose level does not necessarily imply radiosensitivity at other dose levels. This variability in radiosensitivity at low and moderate doses, particularly at cellular level, is increasingly well documented. Research, such as that carried out by the European research platform on Low Dose Initiative (MELODI) and in the medical field (Euramed), is continuing on this subject, and will need to be validated in clinical trials before it can be incorporated into medical practice. The ICRP Task Group (TG111) dedicated to this subject has published a review of the state of knowledge on individual radiosensitivity and the possibilities of predicting it with a view to developing international radiation protection recommendations. At this stage however, no valid biomarker allows for this prediction. The individual response to ionising radiation remains an important subject of research and application in radiobiology and radiation protection (Euratom 2021-2022). 1.3.2 – Effects of low doses The linear no-threshold model The linear no-threshold relationship model is used in radiation protection to estimate the probability of risk associated with an exposure to ionising radiation, in line with the principle of precaution. According to this model, the risk is present as soon as exposure occurs, and it is proportional to the dose of radiation received. There are nevertheless many uncertainties. Some consider that the effects of low doses could be higher, while others believe that these low doses could have no effect below a certain threshold, and some others even assert that low doses have a beneficial effect. Research in molecular and cellular biology is progressing, as are epidemiological surveys of large cohorts. The ICRP considers that the hypothesis of this relationship, used to model the effect of low doses on health (see point 1.2), constitutes a cautious basis in radiation protection for managing the risks due to exposure to ionising radiation. It enables decision-makers to establish an appropriate and cautious radiation protection framework, while remaining sensible given the uncertainties associated with the complexity of DNA repair and mutation phenomena and the methodological limitations of epidemiology, despite the progress of research in molecular and cellular biology. HIGHLIGHT No. 1 Role and main current developments at the ICRP The International Commission on Radiological Protection (ICRP) is an international organisation that drafts and publishes recommendations aimed at improving radiation protection for people (the public, workers, patients) and the environment, in all its dimensions (health risk assessment, dosimetry, medical applications, protection systems). Its recommendations are mainly based on the results of the most recent research work and represent an important foundation on which the vast majority of national and international regulations in the field of radiation protection are based. In addition to assessments of specific elements of its radiation protection system, ICRP regularly publishes general recommendations that form the framework of this system. The latest edition is Publication 103, published at the end of 2007 (ICRP 103). In 2021, ICRP launched a project to revise this document, with the aim of publishing it early in the next decade. Much of the work in progress concerns the effects of ionising radiation, including clarification of the classification of the effects of ionising radiation on health, in particular long-term non-carcinogenic effects (e.g. cardiovascular diseases), updating of the calculation of radiological detriment (i.e. the relationship between exposure and the resulting risk of cancer) and clarification of the risk assessment method for non-human living species. Some fifteen ASNR experts are involved in this review work. Medical electroradiology technician wearing a passive integrating dosimeter on his chest. 110 ASNR Report on the state of nuclear safety and radiation protection in France in 2025
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