Dr. Tsubokura's Radiation Lecture Vol.18

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

35. The reference value is not the line that differentiates between safe and dangerous radiation levels

A variety of “reference values” are used under the radiation protection guidelines in Japan, including annual radiation levels of 1 millisievert and 20 millisieverts and 100 becquerels per 1 kilogram of specific food. As you encounter various values in different radiation units in your daily life, you may find it difficult to understand how a safe level of radiation is expressed in each unit.

Although they are often misunderstood, these reference values are not the borderlines that differentiate between “safe” and “dangerous” radiation levels.

For example, an annual additional radiation dose of 1 millisievert is still significantly lower than the level that would increase the risk of developing health concerns, including cancer. Radiation exposure from naturally-occurring sources varies from place to place. Because of this, there is a range of the level of air radiation dose rate even within the same country, up to approximately 1 millisievert.

Of course, this does not suggest that we should not care about our level of radiation exposure. However, a clear boundary that differentiates between safe and dangerous levels of radiation does not exist, and it is more reasonable to understand that the reference value indicates the ideal value that we should aim to achieve in the long term.

36. Artificial and natural occurring radiation are the same

I suppose many of you heard the names of radioactive substances, such as cesium and strontium, for the first time in your lives after the Fukushima Daiichi nuclear disaster. However, these artificial radioactive substances did not appear in our living environment for the first time because of the accident in Fukushima.

The Chernobyl accident and nuclear weapon tests have repeatedly spread these artificial radioactive substances all over the world.Notably, the several hundred nuclear weapon tests conducted during the 1960s spread significant amounts of cesium, strontium, and plutonium, and we can still find evidence of them in the soil and our food. However, the artificial radioactive substances spread from the events mentioned above and the natural radioactive substances that exist in our environment have the same impact on our body.

Even though their names are different, they emit the same ionizing radiation rays.Our body cannot differentiate between natural and artificial radiation. This is why the extent of the exposure dose determines the impact of radiation. ---------------------------------------------------------------------------------------------------------------------------------------

The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on September 6th ,13thth 2015, and was reproduced for MRIC Global under the author's permission.

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