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Scientific or Unscientific: Divided Views on the Effects of Radiation Exposure from the Nuclear Power Plant Accident

October 6, 2022
Last March, the United Nations Scientific Committee on the Effects of Atomic Radiation, a group of scientists from Europe, the United States, Japan, and other countries, released a report stating that the high incidence of thyroid cancer among young people in Fukushima Prefecture was not caused by exposure to radiation from the nuclear accident, but by highly sensitive testing. Researchers in Japan disagree with this report. They say that the report, which is supposed to be scientific, is based on “unscientific” analysis. What are the contents of the report?

　In July, the Scientific Committee held a dialogue meeting in Iwaki City, Fukushima Prefecture, regarding the “2020/21 Report,” which was released last March. Gillian Haas, former chairperson of the committee, proudly stated, “This report is a reliable, independent, and up-to-date assessment.

　The report aims to “provide a more realistic assessment of radiation doses” than the 13th edition, which was released in 2002. The report took into account Japan’s unique dietary habits and other factors, and revised the estimates of radiation doses from eating contaminated food and other factors.

　For example, the coefficient for estimating radiation doses has been reduced to half that used in the 2001 edition, based on the assumption that kelp, which is traditionally consumed by Japanese people, contains high levels of stable iodine and is therefore unlikely to contain radioactive iodine, which can cause thyroid cancer. The radiation dose from food during the evacuation was revised to be “negligible,” and the effect of the evacuation of people indoors on reducing radiation exposure was estimated to be higher than in the 13th edition.

　As a result, the average radiation doses to the thyroid gland during the first year after the accident ranged from 1.2 to 30 millisieverts for one-year-olds in the prefecture and from 1 to 22 millisieverts for ten-year-olds, with the lowest values being about one-tenth of those in the 13th edition. Mr. Haas said at the dialogue meeting, “Overall, the radiation doses are extremely low. The possibility of an increase in cancer incidence in susceptible infants and children is not discernible,” he stressed.

　Since the nuclear accident, more than 300 people in the prefecture have been diagnosed with thyroid cancer or suspected cancer. This is a high incidence compared to the usual rate of 1 to 2 per million people. The report concluded that it is highly likely that the thyroid cancer was detected by highly sensitive ultrasound screening.

　　　　　◇ ◇A group of researchers in Japan

　A group of researchers in Japan has voiced doubts about the contents of the report.

　At an online press conference held at the end of August, Tadashi Motoyuki, professor emeritus of radiobiology at Osaka University, criticized the report, saying that it “drastically underestimates [radiation doses] by using the minimum or lower values that can be estimated for various factors related to radiation exposure.

　Motoyuki first pointed out the problem of the “kelp effect,” which led to the lowering of radiation doses in the 2008/21 edition.

　The report cited as supporting data a study of only 15 people 55 years ago, which “is not helpful at all,” Motoyuki said. Due to changes in dietary habits, the most recent iodine intake of Japanese people cannot be said to be higher than the world standard, and the assessment is not based on facts, he said.

　As for exposure to radiation from food during the evacuation, it is clear that contaminated vegetables and other products were on the market immediately after the accident, and Motoyuki points out that this goes against the precautionary principle of adopting maximum values for uncertain items.

　The overdiagnosis theory, which was cited in the report as the cause of the high incidence of cancer, is also viewed with suspicion, as it “has not been scientifically verified at all” (Professor Toshihide Tsuda of Okayama University).

　At a press conference in early August, Dr. Yasuyuki Taneichi, a physician, explained that in Fukushima Prefecture, the size of thyroid cancer tumors is inspected based on strict standards to prevent overdiagnosis. In particular, he said that nodules smaller than 5 mm are not scrutinized closely, and that this does not constitute overdiagnosis, which he said detects small, non-life-threatening cancers.

　He also introduced a report that the use of highly sensitive equipment has reduced the number of cases that lead to surgery, as the detailed morphology of the cancer can now be determined. The report criticized the use of highly sensitive instruments, saying that they prevent overdiagnosis and that the report says the opposite.

　The Scientific Committee refrained from giving a detailed response to these points. Former Chairman Haas said during the interactive meeting that the report is a robust document and that its findings will not change in the future. (Tetsuya Kasai, Keitaro Fukuchi)

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　The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was established in 1955, and as of June of this year, 31 countries, including Europe, the United States, and Japan, are members. UNSCEAR’s role is to review papers and other information and compile scientific evidence on the effects of radiation exposure on human health. After the accident at the Fukushima Daiichi Nuclear Power Plant, the Japanese government supported the preparation of the report to “dispel excessive anxiety about the effects of radiation,” contributing 71 million yen in FY13 and 70 million yen in FY17. The government has also used the report and other documents to deny any health damage caused by exposure to radiation in Fukushima.
https://www.asahi.com/articles/ASQB57VYKQ9GUGTB005.html?fbclid=IwAR3BN6Y8JaPJNlyIUPGeOub7OwQvaW9kPy6evxYvVV2ZX58fweZpoabGVZ4

October 8, 2022 Posted by dunrenard | Fuk 2022 | Experts, Fukushima Daiichi, Nuclear Disaster, Radiation Effects, UNSCEAR | Leave a comment