ASN Report 2017

48 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 01  - Nuclear activities: ionising radiation and health and environmental risks The evaluation of the risk of lung cancer due to radon 2 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 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 uraniumminers 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, after tobacco, radon constitutes the highest risk factor in lung cancer. In metropolitan France, about 19 million people spread over some 9,400 municipalities are potentially exposed to high radon concentrations. According to InVS (French Health Monitoring Institute) figures from 2007, 1,200 to 2,900 deaths from lung cancer can be attributed each year in France to radon exposure in the home, that is to say 4 to 10% of deaths due to lung cancer (30,555 deaths, INCa [National Cancer Institute] – 2015). A national plan for managing radon-related risks has been implemented since 2004 on the initiative of ASN and is updated periodically (see point 3.2.2). 1.3 Scientific uncertainties and vigilance The action taken in the fields of nuclear safety and radiation protection in order to prevent accidents and limit detrimental effects has led to a reduction in risks but not to zero risk, whether in terms of the doses received by workers or those associated with discharges and releases from BNIs. Many uncertainties persist; they induce ASN to remain attentive to the results of scientific work in progress in radiobiology and radiopathology for example, with possible consequences for radiation protection, particularly with regard to management of risks associated with low doses. One can mention, for example, several areas of uncertainty concerning radiosensitivity, the effects of low doses, the existence of signatures (specific mutations of DNA) that could be observed in radiation-induced cancers and certain non- cancerous diseases observed in radiotherapy follow-ups. 1.3.1 Radiosensitivity The effects of ionising radiation on personal health vary from one individual to the next. Since it was stated for the first time by Bergonié and Tribondeau in 1906, it is for example known that the same dose does not have the same effect when received by a growing child or by an adult. 2. Radon is a natural radioactive gas, a daughter product of uranium and thorium, an emitter of alpha particles and is classified as a known human pulmonary carcinogen by the International Agency for Research on Cancer - IARC. The variability in individual radiosensitivity to high doses of ionising radiation has been extensively documented by radiotherapists and radiobiologists. High levels of radiosensitivity have been observed in persons suffering from genetic diseases affecting the repair of DNA and cellular signalling; in these individuals they can lead to “radiological burns”. At low doses, there is both cell radiosensitivity and individual radiosensitivity, which could concern about 5 to 10% of the population. Recent methods of immunofluorescence of molecular targets for signalling and repairing DNA damage help to document the effects of ionising radiation at low doses, reducing the detection thresholds by a factor of 100. The biochemical andmolecular effects of a simple X-ray examination then become visible and measurable. The results of the research work conducted using these new investigationmethods must still be confirmed in the clinical environment before being integrated into medical practices. The monitoring of individual radiosenstivity in a medical treatment context through validated tests is not yet fully operational despite the progress of ongoing research. After the publication in 2014 of the conclusions of the seminar ASN organised on 16th December 2013, ASN remains attentive to progress in the knowledge and international reflections (ICRP in particular) to prepare for the ASN regulations that might or will have to be issued. At this stage, there should be no unnecessary, that is to say without good reason, exposure of individuals to ionising radiation. Children should receive particular attention when exposed to ionising radiation for medical purposes. 1.3.2 Effects of low doses The Linear No-Threshold (LNT) relationship. The hypothesis of this relationship, adopted to model the effects of low doses on health (see point 1.2), albeit practical from the regulatory standpoint and albeit conservative from the health standpoint, is not as scientificallywell-grounded asmight be hoped for. Some feel that the effects of low doses could be higher, while others believe that these 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. But facedwith the complexity of the DNA repair andmutation phenomena, and the methodological limitations of epidemiology, uncertainties remain and the public authorities must exercise caution. 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 exposure due to external irradiation (external exposure) received in a few fractions of a second at high dose and high dose rate. The studies carried out in the countries most affected by the Chernobyl accident (Belorussia, 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 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.