Dr. Tsubokura's Radiation Lecture Vol.7

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

13. Cesium is the primary causes of radiation exposure in our daily life

There are various radioactive substances, such as cesium, potassium, strontium, and tritium.Although their name is different, they emit the same type of radiation rays, also known as alpha, beta, or gamma rays.

That is why we cannot tell the types of radioactive substances from radioactive rays which hit our bodies. As I have highlighted in the previous article, the amount of radioactive substance is the point of focus, when we think about their impact on our body.

Some of you might wonder whether we do not have to think about strontium and plutonium. If the levels of these radioactive substances are as high as that of cesium, we need to think about the health impact of such substances. However, in our living environment, cesium composes a predominant part of the radioactive substances among those disseminated following the 2011 nuclear power plant accident.

Therefore, food contamination test focusing on radioactive cesium can significantly prevent radiation exposure.

14. Half-life and the impact level are irrelevant

Radioactive substances gradually lose their power as they emit radiation around them. The time taken to halve their energy is called "half-life."

For example, the half-life of cesium 137, which frequently appear in the news, is about 30 years. Then, which radioactive substance is more harmful to our bodies, the one with a longer half-life, or one with a shorter half-life? If the half-life is more prolonged, would it be harmful as a body is exposed to the radiation continuously for a longer term than the one with short half-life? Would substances with a shorter half-life cause more impact with the rapid exposure in the short term? Or, can the effect be smaller because the radiation quickly disappears?

None of the above is correct.

In short, the impact of radiation is determined by the extent of exposure dose. If the hourly exposure is small, the total impact of long-term exposure can be low. And conversely, if the hourly exposure is extensive, the effect can be also higher even in the short term.

By the way, the half-life of radioactive iodine is about 8 days, and the one of radioactive potassium contained in our body is about 1.3 billion years.​

----------------------------------------------------------------------------------------------------------------------The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on April 5th and 12th 2015, and was reproduced for MRIC Global under the author's permission.