Dr. Tsubokura's Radiation Lecture Vol.143
Author: Masaharu Tsubokura M.D., PhD.
Editors: Akihiko Ozaki M.D.,PhD., Yuki Senoo MUDr.
285. Cancer risk from nuclear disaster compared to that associated with atomic bomb radiation exposure
July 05, 2020
The current understanding of the cancer risk associated with radiation exposure is that when someone is exposed to a higher dose of radiation, there is a higher probability of developing cancer in the future. This is because radiation exposure damages genes (mutations), leading to cancer development.
Cancer cells are often compared to an uncontrollable car with broken accelerators and brakes. Unlike normal cells in our body, since cancer cells have uncontrollable accelerators or brakes, they cannot operate in a manner harmonious with their surrounding cells and continue to grow irregularly in various parts of the body. The terms “genetic damage” and “mutation” indicate the car’s state, such as constantly pressed accelerators and broken brakes.
However, this is just a basic concept underlying the cancer risk associated with radiation exposure. The validity of this concept has been demonstrated through an investigation on radiation exposure and its real-life health effects.
One notable example is the data on cancer incidence among the atomic bomb survivors of Hiroshima and Nagasaki. The investigation results showed that those exposed to very high doses of radiation (several hundreds of millisieverts or more) had an increased incidence of developing cancer. Furthermore, the result also demonstrated that those who received radiation exposure less than 100 millisieverts had no apparent increased incidence of developing cancer. This investigation did not provide an indication of genetic effects in the survivors’ offspring.
This is the major reason why the radiation exposure caused by the Fukushima Daiichi nuclear power plant accident is not considered a factor that increases the incidence of cancer.
286. There is no indication of genetic effects in the offspring of atomic bomb survivors
In the present day, we understand that as radiation exposure increases, so does the probability of developing cancer in the future. This idea comes from the reasoning that radiation damages (mutates) the genes of cells, which will lead to the development of cancer.
On the other hand, mutations in germ cells may cause adverse genetic effects in future generations. As in the case of cancer, the genetic effects associated with radiation exposure are thought to occur in a "stochastic” manner, which means that exposure to a higher dose of radiation increases the probability that adverse genetic effects will occur.
As such, radiation exposure’s genetic effects are considered to have a “stochastic effect.” However, no genetic effects in the offspring (the second generation exposed to radiation) of atomic bomb survivors in Hiroshima and Nagasaki have been observed. Similarly, the survivors exposed to radiation less than 100 millisieverts had no apparent increased incidence of developing cancer.
The radiation air dose rate in Fukushima prefecture caused by the 2011 Fukushima Daiichi nuclear accident is much lower than the air dose rate caused by the atomic bomb in Hiroshima and Nagasaki. Therefore, it can be concluded that the living environment in Fukushima prefecture is nowhere near a concerning level when it comes to the health effects on future generations.
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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 7th June and th June, 2020 was reproduced for MRIC Global under the author's permission.