LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT Dose, dose rate and duration of exposure The epidemiological studies performed on individuals exposed to the Hiroshima and Nagasaki bombings have given a clearer picture of the effects of radiation on health, concerning exposures due to external irradiation (external exposure) received in a few fractions of a second at high dose and high dose rate(5) of ionising radiation. The studies carried out in the countries most affected by the Chernobyl accident (Belarus, Ukraine and Russia) were also able to improve our understanding of the effects of radiation on health caused by exposure through internal contamination (internal exposure), more specifically through radioactive iodine. Studies on nuclear industry workers have given a clearer picture of the risk associated with chronic exposures at low doses established over many years, whether as a result of external exposure or internal contamination. Hereditary effects Hereditary effects have been documented in experimental work on animals; more specifically, the mutations induced by ionising radiation in germ cells (cells that develop into reproductive cells: spermatozoa or ova) can be transmitted to the progeny. The occurrence of possible hereditary effects from ionising radiation has not been demonstrated in humans. Such effects have not been observed among the survivors of the Hiroshima and Nagasaki bombings. An ICRP Task Group, TG121, is currently working on this subject. Environmental protection The purpose of radiation protection is to prevent, mitigate and limit the exposure of individuals to ionising radiation, directly or indirectly, including through deleterious effects on the environment. Over and beyond environmental protection aiming at the protection of humans and present or future generations, the protection of non-human species as such forms part of the environmental protection prescribed in the French constitutional Charter for the Environment. Protection of nature in the specific interests of animal and plant species (see chapter 3, point 4.2.4) has been the subject of several publications since 2008 (ICRP 108, 114, 124 and 148). Post-accident situations, characterised by long-term contamination of the environment, are ideal settings for understanding the effects of ionising radiation on living organisms, through the study of biodiversity and the functioning of ecosystems. This knowledge is essential for assessing the robustness of the data used by the environmental radiation protection system, which has historically been based on laboratory experiments. However, little is known about the effects of ionising radiation on non-human species, even though major accidents, particularly the Fukushima Daiichi accident, have given rise to high social and scientific expectations in this area. In this context, ASNR is leading the BEERAD research programme, in collaboration with INRAE and IER, which aims to study the impact of ionising radiation on bees. The BEERAD project combines laboratory 5. The radioactive dose rate determines the absorbed dose (energy absorbed by the material per unit mass and time). It is measured in Gray per second (Gy/s) in the International System of Units (SI). It is used in physics and radiation protection. 6. Exposure of the French population to ionising radiation – Results for 2014‑2019, IRSN, 2021. and field experiments around the Fukushima Daiichi NPP. Initial results show a negative effect of ionising radiation on the reproduction of queen bees exposed in the laboratory for a fortnight. Experiments in the field have shown that beehives kept close to the power station for five months had caesium levels in their honey that exceeded the limit values for food consumption in Japan. Many other results are currently being analysed. This project offers prospects for better modelling of post-accident impacts on major ecological processes. 1.3.3 – Molecular signature in radiation-induced cancers It is currently impossible to distinguish radiation-induced cancer from cancer unrelated to ionising radiation. The lesions caused by ionising radiation appear to be similar to those of normal cellular metabolism, with the involvement of free radicals – oxygenated in particular – in both cases. Furthermore, neither anatomopathological examinations nor research for specific mutations have been able to distinguish radiation-induced tumours from sporadic tumours. During the first stages of carcinogenesis (process of cancer formation), a cell presents a particular combination of DNA lesions that enables it to escape from the usual control of cell division. Several dozen to around a hundred DNA lesions (mutations, breaks, etc.) are required. All the agents capable of damaging cellular DNA (tobacco, alcohol, various chemical substances, ionising radiation, high temperature, other environmental factors, notably nutritional and free radicals of normal cellular metabolism, etc.) contribute to cellular ageing and to carcinogenesis. Consequently, in a multi-risk approach to carcinogenesis, can we still talk about radiation-induced cancers? Yes, given the quantity of epidemiological data which indicate that cancer frequency increases when the dose increases, with the other main risk factors taken into account. However, the radiation-induced event can also in certain cases be the only event responsible (radiation-induced cancers in children). Highlighting a radiological signature of cancers, that is to say the discovery of markers that could indicate whether a tumour has a radiation-induced component or not, would be of considerable benefit in the evaluation of the risks associated with exposure to ionising radiation, but has not been demonstrated to date. The multifactorial nature of carcinogenesis suggests the need for a precautionary approach towards all risk factors. This is particularly important in persons displaying high individual radiosensitivity and for the most sensitive organs such as the breast and the bone marrow, and all the more so if the persons are young. Here, the principles of justification and optimisation become all the more relevant (see point 3.1). 2 – The different sources of ionising radiation 2.1 Natural ionising radiation In France, exposure to the different types of natural radioactivity (cosmic radiation, terrestrial radiation such as that linked to the incorporation of natural radionuclides contained in foodstuffs and drinking water and that associated with the presence of radon in the home) represents on average 76% of the total annual exposure(6). 2.1.1 – Cosmic radiation Cosmic radiation is made up essentially of ions. They have a directly ionising component and an indirectly ionising component due to the presence of neutrons (the “neutron component”), which vary according to altitude and longitude. Considering the altitude of each municipality, the average time spent inside the home and a housing protection factor of 0.8 (housing attenuates the ionic component of cosmic radiation), ASNR ASNR Report on the state of nuclear safety and radiation protection in France in 2025 111 01 05 09 02 06 10 03 07 11 13 04 08 12 A / Z
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