GENERAL
The concepts of “Optimization” and “Justification” have been developed and applied by ICRP to determine the dose limit for radiation and nuclear facility workers. Then, the reduced dose limit has been proposed for the members of public, which was used as the dose limit at the site boundary to approve nuclear facilities at the stages of planning, constructions and start of operations. Therefore, the both concepts of “Optimization” and “Justification” are incompatible to the “Existing exposure situation” which is far from any optimal and justifiable regional environments. For a person who has higher radio-sensitivity, any additional doses with a level of 1 mSv/y is threat and danger. The “reference level” with the dose rates of 20 mSv/y or 10 mSv/y are so high for human beings and their environment to live in a safe and with good health. These radiation levels can never work to protect people from the ionizing radiations. At the highest, or at least, 1 mSv/y should be applied for the members of public as the “reference level”.
From the viewpoint of radiological protection, expecting radiation dose should be reduced by evacuation, house-moving and decontaminations. Contrary to the descriptions in the paper entitled “Individual external dose monitoring of all citizens of Date City by passive dosimeter 5 to 51 months after the Fukushima NPP accident (series): II. Prediction of lifetime additional effective dose and evaluating the effect of decontamination on individual dose”, the environmental decontamination has partial effect to decrease the doses of residents determined by glass dosimeters in Date-city, Fukushima Prefecture, Japan, as shown in Fig. 6.
[1] Makoto Miyazaki and Ryugo Hayano, Journal of Radiological Protection, Volume 37, Number 3, 623-634.
PART on the Thyroid cancer (1)
In the paragraph of 201, the draft said as “(201) Specific monitoring programmes for the thyroid may be useful to detect severe thyroid disorders as early as possible. However, such monitoring should be organised ensuring that benefit outweighs harm at the population level (Togawa, 2018). In this regard, a long-term thyroid health monitoring programme should only be conducted for those individuals exposed in utero or during childhood or adolescence with 100–500 mGy absorbed dose to the thyroid.”
The absorbed dose of 100 mSv for the thyroid is too high to use as the dose-limit for any thyroid monitorings. Many childhood and adolescent thyroid cancers have been observed after the Chernobyl accident from whose thyroid doses were lower than 100 mSv [2]. After the accident of TEPCO Fukushima Daiichi Nuclear Power Plant, any systematic and comprehensive measurements on thyroid dose for residents were not carried-out. It is terribly difficult to perform precise dose estimations after the large nuclear accident. The monitoring of thyroid should be widely recommended among residents after the nuclear accident.
[2] Tronko Ph.D et at Thyroid carcinoma in children and adolescents in Ukraine after the Chernobyl nuclear accident
PART on the Thyroid cancer (2)
In the paragraph of (B 42), the draft denies the relationship between observed excess thyroid cancers and the TEPCO nuclear accident, as “(B 42) The first and second rounds of the thyroid ultrasound examinations were completed in March 2014 and 2016, respectively. Children will continue to have ultrasound examinations biennially until they reach 20 years of age, and every 5 years thereafter. Childhood thyroid cancer cases found in Fukushima Prefecture are unlikely to be the result of radiation exposure after the accident. ”
Studies by different authors have demonstrated the causal relationship between the TEPCO nuclear accident and the excess of thyroid cancers in Fukushima Prefecture [3-6]. The part of “Childhood thyroid cancer cases found in Fukushima Prefecture are unlikely to be the result of radiation exposure after the accident” should be deleted. Relating to this, ICRP should pay a special attention on the paragraphs of 111&112 in UNSCEAR 2016 white paper, where UNSCEAR had failed to correctly reconstruct the scientific discussions which were made in the academic and expert journal of “Epidemiology”, especially ignoring the Authors Response [4].
[3] Tsuda, T., A. Tokinobu, E. Yamamoto et al. Thyroid cancer detection by ultrasound among residents ages 18 years and younger in Fukushima, Japan: 2011 to 2014. Epidemiology 27(3): 316-322 (2016).
[4] Tsuda, T., A. Tokinobu, E. Yamamoto et al. Response to the Commentary by Professor Davis and the Seven Letters. - a well-known fact should be disseminated to remedy the problems. Epidemiology 27(3) e21-23 (2016).
[5] Toshiko Kato, Re: AssociationsBetween Childhood Thyroid Cancer and External Radiation Dose After the Fukushima Daiichi Nuclear Power Plant Accident, Epidemiology 30(2) e9-e10 (2018)
[6] Yamamoto H, Hayashi K, Scherb H. Association between the detection rate of thyroid cancer and the external radiation dose-rate after the nuclear power plant accidents in Fukushima, Japan. Medicine 2019;98:37(e17165).