Dr. Tsubokura's Radiation Lecture Vol.145

Author: Masaharu Tsubokura M.D., PhD.

Editors: Akihiko Ozaki M.D.,PhD., Yuki Senoo MUDr.

289. The health effects of radiation are overestimated

Although we still do not know whether there are some health risks of low-dose radiation, this does not mean that we have no idea about whether low-dose radiation can cause any future health issues. While it is difficult to completely disprove the health impacts of low-dose radiation, the results of prior studies strongly suggest they are minimal.

　On the other hand, effective radiation control measures cannot be constructed solely based on the belief that the health risks of low-dose radiation are nonzero. Therefore, it is necessary to determine some rough figures to indicate the health risks of low-dose radiation exposure.

　　　　In existing research, limited information is available regarding the risk of developing cancer among the survivors of the atomic bombings in Hiroshima and Nagasaki who received low-dose radiation exposure. On the other hand, the research showed a significant increase in cancer incidence among those who received high levels of radiation.

　　　　Therefore, radiation control measures are determined based on the hypothesis that the known health risks of high-dose radiation exposure will occur in proportion to the level of radiation when receiving low doses of 100 millisieverts or less. Thus, the health problems caused by low-dose radiation exposure are estimated using the known health risks of high-dose radiation. The basic idea is that the negative health risks of a half-dose of radiation exposure will be half, and one-tenth for one-tenth of a higher amount of radiation exposure.

　　　　There is a criticism that this hypothesis is not scientific. However, in terms of radiation protection, this method for constructing radiation safety measures is internationally accepted because it is safer to overestimate the harmful health risks of radiation exposure.

290. Health risks of low-dose radiation are hypothesized

While it is difficult to completely prove or disprove the detrimental health risks of low-dose radiation, effective radiation control measures cannot be based on vague standards. For this reason, radiation control measures are determined based on the hypothesis that the known health risks of high-dose radiation will occur in proportion to the level of radiation when receiving low doses of 100 millisieverts or less.

The basic principle is that the health risk of a half-dose of radiation exposure will be half, and it will be one-tenth for one-tenth of a corresponding high amount of exposure. In other words, what is known about the health impact of high-dose radiation exposure is applied to estimate the health risks of low-dose exposure.

　It should be noted that this estimation method is only used for determining radiation protection and safety measures. Hence, such estimates are not consistent with findings from other fields of science.

　For example, previous studies have revealed that low-dose radiation exposure does not lead to development of cancer, since a threshold level of radiation is needed to cause cancer. The examples of specific types of cancer associated with radiation exposure above the threshold level are as follows: bone cancer can be caused by ingesting fluorescent paints containing radioactive materials, liver cancer is often caused by certain contrast agents used decades ago, and some blood and ovarian cancers have been demonstrated in animal studies. To the present day, we are unable to confirm the negative health risks of low-dose radiation exposure. It is believed that this is because cells in our body can repair the damage caused by low-intensity radiation and replace damaged tissue with new cells.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 2nd and 9th, August, 2020 was reproduced for MRIC Global under the author's permission.