2. The different sources of ionising radiation 6. Exposure of the French population to ionising radiation – Results for 2014-2019, IRSN, 2021. 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 66% 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), 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. External exposure to gamma rays of terrestrial origin Based on the results of a) ambient gamma dose rate measurements taken in France inside buildings, b) the mapping of the uranium potential of geological formations, c) a correlation between the gamma dose rate of terrestrial origin outside the home and inside the home, and d) assumptions on the time spent by the population inside and outside the home (92 % and 8% respectively), IRSN estimates that the average annual effective dose due to external exposure to gamma radiation of terrestrial origin in France is about 0.63 mSv per person per year. It varies from 0.30 mSv/year to 2.0 mSv/year depending on the municipality. Exposure linked to the incorporation of radionuclides of natural origin The average internal exposure due to the incorporation of radionuclides of natural origin is estimated at 0.55 mSv/year. The two main components of this exposure are the incorporation through foodstuffs and drinking water of potassium-40 (0.18 mSv) and descendants of the uranium and thorium chains (0.32 mSv). Depending on the individual consumption habits, in particular the consumption of fish, seafood and tobacco, this exposure can vary greatly: from 0.4 mSv/year up to more than 3.1 mSv/year, respectively, for people who do not consume these products and those who consume them in large quantities. Waters intended for human consumption, in particular groundwater and mineral waters, become charged in natural radionuclides due to the nature of the geological strata in which they lie. The concentration of uranium and thorium daughters and of potassium-40 varies according to the resource exploited, given the geological nature of the ground. The average effective dose linked to the decay products of the U‑Th chains in drinking water is estimated by IRSN at 0.01 mSv/year. A high value of 0.30 mSv/year is retained to illustrate the variability of this exposure. 2.1.3 Radon Some geological areas have a high radon exhalation potential due to the geological characteristics of the ground (granitic bedrock, for example). The concentration measured inside homes also depends on the tightness of the building (foundations), the ventilation of the rooms and the life style of the occupants. National measuring campaigns have enabled the French départements to be classified according to the radon exhalation potential of the ground. In 2011, IRSN published a map of France considering the radon exhalation potential of the ground, based on data from the French Geological and Mining Research Office (BRGM). Based on this, a more fine-grained classification, by municipality, was published through the Interministerial Order of 27 June 2018 (see search engine by municipality and mapping accessible on asn.fr and irsn.fr). Based on the available measurement results and the mapping of the geogenic radon potential of the territory, the average time spent inside the home and assumptions on the type of housing concerned (collective or individual), IRSN has estimated the average radon concentration for each municipality: the average concentration of radon-222 inside housing in metropolitan France, weighted for the population and type of housing, is 60.8 Bq/m3. Using the dose factor of ICRP 65 currently in effect, the effective average dose per inhabitant is estimated at 1.45 mSv/year. The effective dose varies from 0.31 mSv/year to 19 mSv/year depending on the municipality. IRSN has moreover published an assessment of the consequences of the adoption of new coefficients published by the ICRP in its publication 137 (see box page 102). The new obligation for radon detector analysis laboratories to send IRSN the measurement results and the expected results of action 7 of the fourth French action plan for management of the radon risk (see point 3.2), relative to the defining of organisation methods for collecting the radon measurement data should improve knowledge of radon exposures in France. 2.2 Ionising radiation arising from human activities The human activities involving a risk of exposure to ionising radiation, called nuclear activities, can be grouped into the following categories: ∙ operation of BNIs; ∙ small-scale nuclear activities; ∙ removal of radioactive waste; ∙ management of contaminated sites; ∙ transport of radioactive substances; ∙ activities enhancing natural ionising radiation. 104 ASN Report on the state of nuclear safety and radiation protection in France in 2022 • 01 • Nuclear activities: ionising radiation and health and environmental risks 01
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