Dr. Tsubokura's Radiation Lecture Vol.39

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

77. Much higher radiation exposure could result in health effects for the affected population

The previous article’s author explained that a significantly high level of radiation exposure definitely causes various symptoms, such as hair loss, bleeding, diarrhea, and burns (erythema). These phenomena are called “deterministic effects.” On the other hand, the author stated that a sufficiently low level of exposure will never result in such adverse health effects.

Then what is the threshold radiation dose that the body can be exposed to without such adverse health effects?

The answer is several hundred millisieverts. This level of radiation exposure is equivalent to about 1 million times the hourly exposure dose in the habitable area in Fukushima Prefecture as of 2016. It is also equivalent to about 100 years of such a dose. Additionally, deterministic effects will only appear when one’s body is exposed to this level of radiation all at once.

People need not worry about developing deterministic effects when they only participate in restoration work or decontamination work in the difficult-to-return-to or restricted areas in Fukushima Prefecture because of the gap between the actual the radiation dose in these areas and that required to develop deterministic effects in humans.

78. A sufficiently low level of radiation exposure never causes health disturbances

According to the previous articles’ authors, regarding deterministic effects, repeated significantly high levels of radiation exposure cause symptoms such as hair loss, bleeding, diarrhea, and burns (erythema), but a sufficiently low level of exposure will never result in such adverse health effects.

Then why does a significantly high level of radiation exposure cause bleeding disorders, such as nosebleeds?

In the human body, components of blood are produced in bone marrow, inside the bones. When people are exposed to a significantly high level of radiation, the cells that produce blood components are damaged, and their functions are impaired. During this damaging process, platelets, which stop bleeding, decrease in number, resulting in easy bleeding.

However, this adverse health effect only occurs when one’s body is exposed to over several hundred millisieverts of radiation exposure. In our daily lives, we never experience nosebleeds due to the radiation exposure after the nuclear power plant accident in Fukushima. It is one of the deterministic effects, a set of symptoms that never appear in anyone who receives only a low level of radiation exposure.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on June 26th and July 3rd 2016 was reproduced for MRIC Global under the author's permission.