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Dr. Tsubokura's Radiation Lecture Vol.3

Author: Masaharu Tsubokura

Editors: Izumi Yoshida, Mariko Irie, Yuki Senoo

5. Potassium is not the only radioactive substance

 A little potassium contained in animals, plants, and foods is radioactive potassium, and we are exposed to radiation through ingestion in our daily diet. Foods contain not only radioactive potassium but also radioactive polonium and radioactive carbon, and we are exposed to radiation from before the nuclear accident.

The level of radioactive potassium increases when we eat lots of vegetables and the level of radioactive polonium increases when we eat seafood. Japanese people, who eat a lot of seafood, are known to have much higher radiation exposure in comparison with the world average.

However, this does not mean that we should not eat vegetables or seafood. Balance is crucial in the diet. Even if there is food contamination in Fukushima, it is a well-known fact that it is sufficiently less than radioactive substances ingested through daily eating habits.

6. Our bodies contain potentially 4000 to 5000 Bq of radioactive substances

 Radioactive substances are also present in our bodies. In my body, 4000 to 5000 Bq of radioactive potassium can be detected, for example, and in an infant, 500 to 1000 Bq can be found. The difference in this value is due to the body size and muscle mass difference.

After the nuclear disaster, many people are suffering from damage caused by misinformation about food with radioactive contamination. However, the most important thing is how much of an additional radioactive dose is in our bodies after this nuclear power disaster because we cannot distinguish between artificial or natural radioactive substances.

When we discuss if there is contamination or not, the presence of radioactive potassium is not the problem, but the effect on the body is substantial.


The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on February 8 and February 15, 2015,and was reproduced for MRIC Global under the author's permission.

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