Christian Streffer, Professor for Medical Radiobiology and Emeritus Member of the Main Commission of ICRP, University Clinics Essen, Germany

This statement is written by a scientist who has worked for more than 50 years in experimental radiobiology (mammalian cells and organisms including humans) with respect to experimental cancer therapy and radiation risk also after prenatal radiation exposure. He has been leader of interdisciplinary projects with philosophers, lawyers, radiologists, engineers, medical doctors, sociologists and psychologists. He has been member and partly chairman of several scientific advisory boards like the German Committee for Radiological Protection (SSK), ICRP and UNSCEAR.

Looking through the published data with respect to the estimated radiation doses and the surveys of health effects caused by the accident of the Fukushima Daiichi Nuclear Power Stations (FDNPS) I come mostly in agreement with the UNSCEAR-Report of December 2013 to the following conclusions:

• Acute health effects which can be caused by exposures to ionizing radiation have not been observed during the first years after the accident. Judging from the world-wide clinical experience with radiation accidents and radiotherapy as well as from experimental data with human tissues, cells as well as with other mammals no acute effects could be expected from the estimated radiation doses. These radiation doses are below the threshold doses for such acute radiation effects.
• The most radiosensitive processes in human life are certainly occurring during the prenatal development in utero. Careful observations and studies of pregnancies (between August 1, 2010 and July 31, 2011) in seven geographic areas of Fukushima prefecture have not shown a significant increase of developmental anomalies in the born children. This is again in agreement with earlier experiences in the dose ranges which have been estimated after the FDNPS accident.
• The most important late effect one has to be afraid of after radiation exposures in the low dose range is the causation of cancer and this can occur under the assumption of the “linear no threshold” (LNT) model even after low radiation doses. The development of cancer occurs years and decades after the radiation exposure.
• The incidence and mortality of cancer is relatively high worldwide in all human societies. The cancers are caused by endogenous, e.g. oxidative metabolism, and exogenous, e.g. lifestyle and a variety of toxic agents. There is no possibility to distinguish between a cancer caused by ionizing radiation or other reasons. The radiation doses estimated for the general population including very young children (infants) and for the involved workers are low in the average. Thus it will not be possible on the basis of present knowledge to observe an increase of cancer by statistical epidemiological methods.
• The best studied cancer after the Chernobyl accident is thyroid cancer. A high risk for this cancer has been seen with children. This risk is very strongly dependent on age with the highest risk in very young children (infants). The radiation dose is extremely high in the thyroid after accidents of nuclear power stations due to the release of radionuclides of iodine (I) especially ¹³¹I from the nuclear reactor. This radionuclide has a physical half-life of only 8 days. Some other iodine radionuclides which are also released from damaged nuclear reactors have an even shorter half-life. The radio-iodine is specifically taken up in the thyroid by inhalation and ingestion and causes a specific radiation exposure in the thyroid.
• This release of iodine has also led to higher and in some individuals extremely high radiation doses after the FDNPS accident. The radiation dose cannot be measured directly but has to be calculated through biokinetic models after measuring the ¹³¹I-incorporation. These measurements only started some weeks after the accident has occurred. The estimates carry some higher uncertainties therefore, as the decay of radionuclides had progressed during the time after the accident. Special attention has to be paid to the thyroid exposure of infants which was low in the average but ranged in few individuals up to 80 mGy. Also with 13 TEPCO-workers very high radiation doses of 2 to 12 Gy have been estimated in the thyroid, again mainly caused by incorporation of iodine radionuclides. These high radiation doses in the thyroid may not only induce cancer but also other thyroid diseases in the workers at later years.
• These careful studies of Japanese and international institutions have shown that no health effects have been observed until now which can be associated with radiation-induced effects. However, some individuals received radiation doses which impose a risk of late effects. A medical follow-up of these individuals is necessary.
• However, the most severe health effects observed after the earthquake, tsunami and FDNPS accident are undoubtedly serious problems of mental and social well-being with the loss of family members, friends, homes and other difficult disturbances. From my own experience I have great understanding for such psychologically caused traumata, as I myself had to leave my home with my family as an 11-year old boy with loss of my father and all property. This was caused by the war.

What are the challenges for the future considering the situation after the FDNPS accident?

• From the viewpoint of radiological science it certainly is necessary to study whether the estimation of radiation doses can be improved. This is especially the case for the measurement of released radionuclides and their incorporation into humans as well as most important to improve the biokinetic models. If such studies are successful it may be possible to re-evaluate the dose estimates of those individuals for whom dose estimates exist which are much higher than the averages.
• Children who received higher thyroid doses (>20 mGy) at the ages up to 1year and up to 10 years at the time of the radiation exposure need a regular medical control with respect to possible abnormalities of the thyroid. Certainly radiological methods should be avoided for these investigations as far as possible, e.g. procedures of nuclear medicine or CT, as repeated radiation exposures of such diagnostic procedures may come into the range of the doses caused by the accident. Furthermore I do not propose a massive screening of all children living in the affected area around FDNPS. When I realize that the thyroid doses estimated after ¹³¹I incorporation measurements of 1-year-old children in Iwaki City were in 85 % of the infants <5 mGy and in 55 % 0 mGy a general screening would not be reasonable unless it is concretely wished by the parents.
• The types of medical control studies are somewhat different with the highly exposed workers who also need a regular medical control of the thyroid and the endocrine system of this organ as the radiation doses of the diagnostic nuclear medical methods or CT will be small in comparison to the radiation dose which these workers received during their services in the damaged FDNPS. The medical control is necessary in these highly exposed workers not only with respect to possible cancer diseases but also other disorders of the thyroid and the connected endocrine system.
• The affected population of the whole region including the workers with their families certainly need professional services (care and counseling) from psychologists, sociologists and may be also religious help in order to find back to normal life and orientation. Such services are apparently planned by the Government of Japan. This individual care has to be done effectively together with radiologists (clinicians and researchers), as further professional information about radiation risks may be very be helpful and is necessary for the understanding what has happened and to which degree there is still a risk.
• From my own experience as chairman of interdisciplinary groups I know: Communication of these problems is difficult, it needs interdisciplinary discussions and counseling in order to build up a culture of confidence. These considerations are essential presumptions for bringing back evacuated people into their home regions. I see with great interest that the Government of Japan has lifted stepwise evacuation orders of certain regions. This certainly can be supported by interactive discussions with stakeholders and the population.
• A great challenge is undoubtedly the decontamination of the highly contaminated areas and the handling of the waste. As I have no personal expertise for these problems, I can only mention these problems without any further comments.
• The repopulation and building up a community with social life can only be successful if people are convinced that possible radiation risks are tolerable. Besides this presumption an excellent infrastructure (e.g. roads, public transport, internet, medical care, good school-system etc.) is necessary for repatriation. However, it is also important to attract young people to start their career in these areas.
• I am living since 40 years in a region in Germany (Essen, “Rhurregion”) where coal and steel was dominant for decades until the end of the sixties but then these industries especially coal mining had no longer a profitable economic fundament. For the necessary changes it has turned out that new high-technologies and institutions of higher education (universities including clinical centers and research, technical high schools etc. became a motor for re-orientation) made the region attractive and offered a large number of qualified jobs.

Needless to say: Such re-establishment can only be done by investing time and money. Apparently the Government of Japan is planning certain steps in this direction which should find strong support.

Related Links: Prof. Christian Streffer's Attendance at the 15th International Congress of Radiation Research ( ICRR ) in Kyoto and courtesy call on Deputy Chief Cabinet Secretary Seko.