DR.TSUBOKURA'S RADIATION LECTURE VOL.166

Author: Masaharu Tsubokura M.D., PhD.

Editor: Yudai Kaneda

331　 The amount of thyroid exposure to radiation is important

June 12, 2021

In March 2021, the UN Scientific Committee on the Effects of Atomic Radiation issued a report titled the “20 Year Report.” In the report, the committee commented that the large number of thyroid cancers found after the accident was probably not related to radiation exposure.

　On the other hand, there is an opinion that the number of thyroid cancer patients found in post-accident examinations is higher than the number of thyroid cancer patients generally known, and that this may be due to radiation exposure.

　However, the number of people who actually have symptoms of any disease and who are subsequently diagnosed with the disease (the commonly known number of patients found in hospitals, etc.) is completely different from the number of patients found when testing is performed on the entire population, regardless of whether they have symptoms. The number of patients who are found will increase significantly if the testing is done extensively and precisely.

　Therefore, simply comparing the number of patients and only discussing whether an increase has occurred is a mistake. When discussing the effects associated with radiation exposure, the most important question is the amount of radiation exposure.

　As the current report says, the estimated thyroid exposure is small and it has been revised to a smaller value than stated in previous reports. It is hard to imagine that the amount of radiation would increase thyroid cancer.

332　 Expanded testing coverage, increased cancer detection

June 19, 2021

In March 2021, the UN Scientific Committee on the Effects of Atomic Radiation released its report on the accident, in which it stated that the high number of thyroid cancers found after the accident is probably not related to radiation exposure.

　To summarize the reasons for view, first, many of the thyroid cancers found since the accident were found too early to be caused by radiation.

Second, the average age of those who have been found to have thyroid cancer since the accident is skewed toward older people, rather than children, who are more susceptible to the effects of radiation.

Third, the genetic abnormalities of thyroid cancer found after the accident are different in type from the genetic abnormalities of thyroid cancer found after the Chernobyl accident and after the atomic bombings in Hiroshima and Nagasaki.

　Fourth, the thyroid exposure was low.

　The Committee then points out that one of the reasons why more thyroid cancers are found after the accident is that the number of patients found when a broad and precise examination is performed on the entire population, with or without symptoms, increases compared to the number of patients found in hospitals after a medical examination.