ASN Report 2020

Epidemiological investigation is complementary to monitoring. Its purpose is to highlight an association between a risk factor and the occurrence of a disease, between a possible cause and an effect, or at least to enable such a causal relation to be asserted with a very high degree of probability. The intrinsic difficulty in conducting these surveys or in reaching a convincing conclusion when the illness is slow to appear or when the expected number of cases is low, as is the case in particular with low exposure levels of a few tens of millisieverts (mSv), must be borne in mind. Cohorts such as those of Hiroshima and Nagasaki have clearly shown an excess of cancers, with the average exposure being about 200 millisieverts (mSv), studies on nuclear industry workers published in recent years suggest risks of cancer at lower doses (cumulative doses over several years). These results support the justification of radiation protection of populations exposed to low doses of ionising radiation (nuclear industry workers, medical personnel, medical exposure for diagnostic purposes, etc.). When there are no data on the impact of low doses on the occurrence of a cancer, estimates are provided by making linear no-threshold extrapolations of the observed effects described for high doses. These models give estimations of the risks run during exposure to low doses of ionising radiation, which nevertheless remain scientifically controversial. Studies on very large populations are currently underway to develop these models. On the basis of the scientific syntheses of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the International Commission on Radiological Protection (ICRP) has published the risk coefficients for death by cancer due to ionising radiation, i.e. 4.1% excess risk per sievert for workers and 5.5% per sievert for the general public (see ICRP Publication 103). 3. Radon is a natural radioactive gas, a progeny product of uranium and thorium, an emitter of alpha particles and has been classified as a known human pulmonary carcinogen by the International Agency for Research on Cancer (IARC) since 1987. The evaluation of the risk of lung cancer due to radon (3) is based on a large number of epidemiological studies conducted directly in the home in France and on an international scale. These studies have revealed a linear relationship, even at low exposure levels (200 becquerels per cubic metre – Bq/m 3 ) over a period of 20 to 30 years. The World Health Organisation (WHO) has made a synthesis of the studies and recommends maximum annual exposure levels of between 100 and 300 Bq/m 3 for the general public. ICRP Publication 115 compared the risks of lung cancer observed through studies on uranium miners with those observed in the overall population and concluded that there was a very good correlation between the risks observed in these two conditions of exposure to radon. The ICRP recommendations consolidate those issued by the WHO which considers that radon constitutes the second-highest risk factor in lung cancer, coming far behind tobacco. Furthermore, for given levels of exposure to radon, the risk of lung cancer is much higher in smokers: three quarters of the deaths by lung cancer that can be attributed to radon reportedly occur in smokers. In metropolitan France, about 12 million people spread over some 7,000 municipalities are potentially exposed to high radon concentrations. According to the national Public Health Agency (ARS – 2018), an estimated 4,000 new cases of lung cancer are caused by radon in metropolitan France each year, far behind the number due to tobacco (the estimated number of new cases of lung cancer in Metropolitan France in 2018 was 46,363). A national plan for managing radon-related risks has been implemented since 2004 on the initiative of ASN and is updated periodically. The 4th plan (2020‑2024) was published in early 2021 (see point 3.2.2). The recommendations of the International Commission on Radiological Protection (ICRP) The ICRP, which published new recommendations for the calculation of effective and equivalent doses (Publication 103) in 2007, is gradually updating the values of the effective dose coefficients for internal and external exposure. Its Publication 137 (2017), entitled Occupational Intakes of Radionuclides – Part 3 , concerns 14 radionuclides, including radon. The doses delivered by radon and its progeny depend on many parameters (variability of exposure situations, individuals, etc.). The preceding dose coefficients recommended by the ICRP (Publication 65, 1993) for exposure to radon and its progeny were based on an epidemiological approach. ICRP Publication 115 (2010) updated the risk of lung cancer associated with radon exposure on the basis of new epidemiological studies. The ICRP had concluded that the risk of death from lung cancer in adults having been chronically exposed to low concentrations of radon was nearly two times higher than that estimated on the basis of the knowledge available in 1993. The dose coefficients for radon taken from ICRP Publication 137 (2017) are based on a dosimetric approach, in the same way as for the other radionuclides. For an equal given level of exposure to radon and its progeny, they lead to a significant increase in the annual effective dose received by workers exposed to radon (nearly two times higher). In view of these developments and pending the updating of the regulations (*) to revise the dose coefficients applicable for radon and its progeny, ASN has asked the Advisory Committee for Radiation Protection in Industrial and Research Applications of Ionising Radiation and for the Environment (GPRADE) to identify the difficulties that could arise from application of the new ICRP coefficients (Publication 137, 2017). The GPRADE submitted its opinion to ASN in 2020. ASN will issue a position statement on this opinion in early 2021 along with the publication of the report and the GPRADE opinion. *Order of 1 September 2003 defining the methods for calculating effective doses and equivalent doses resulting from human exposure to ionising radiation. 104 ASN Report on the state of nuclear safety and radiation protection in France in 2020 01 – NUCLEAR ACTIVITIES: IONISING RADIATION AND HEALTH AND ENVIRONMENTAL RISKS