Hereditary and teratogenic effects 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. But 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 ovules) can be transmitted to the progeny. An ICRP Task Group, TG121, is currently working on the heritable effects and their modes of transmission to future generations. 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 point 3.4) has been the subject of several publications since 2008 (ICRP 108, 114, 124 and 148). 1.3.3 Molecular signature in radiation-induced cancers It is currently impossible to distinguish a radiation-induced cancer from a cancer that is not radiation induced. The reason for this is that the molecular lesions caused by ionising radiation seem no different to those resulting from the normal cellular metabolism, with the involvement of free radicals – oxygenated in particular – in both cases. Furthermore, to date, neither anatomopathological examinations nor research for specific mutations have been able to distinguish a radiation-induced tumour from a sporadic tumour. 6. Exposure of the French population to ionising radiation – Results for 2014-2019, IRSN, 2021. It is known that in the first stages of carcinogenesis (process of cancer formation) a cell develops with a particular combination of DNA lesions that enables it to escape from the usual control of cellular division, and that it takes about ten to one hundred DNA lesions (mutations, breaks, etc.) at critical points to pass through these stages. 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 we can, 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 calls for a cautious approach with respect to all the risk factors, since each one of them could contribute to DNA damage. 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 are more than ever applicable (see chapter 2). 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), the French Institute for Radiation Protection and Nuclear Safety (IRSN) evaluates the average individual effective dose per person in France at 0.31 mSv with a variation of 0.3 to 1.1 mSv/year depending on the municipalities. Passengers and flight crew are exposed during air travel, depending on the flight altitude and the journey, to exposure varying from a few microsieverts (μSv) for short-haul domestic flight within France to nearly 80 μSv for a flight from Paris to Ottawa (Canada). The average annual effective dose received by the population in France is 14 μSv. On account of the increased exposure to cosmic radiation due to extensive periods spent at high altitude, flight personnel must be subject to dosimetric monitoring (see point 3.1.3). 2.1.2 Natural terrestrial radiation (excluding radon) Natural radionuclides of terrestrial origin are present at various levels in all the compartments of our environment, including inside the human body. They lead to external exposure of the population owing to gamma rays emitted by the uranium-238 and thorium-232 daughter products and by the potassium-40 present in the soil. ASN Report on the state of nuclear safety and radiation protection in France in 2023 103 • 01 • Nuclear activities: ionising radiation and health and environmental risks 01 05 15 08 11 04 14 06 07 13 AP 03 10 02 09 12
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