Dr. Tsubokura's Radiation Lecture Vol.35

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

69. The exposure dosage determines the adverse health effects of radiation poisoning

Unstable radioactive substances emit unneeded protons, neutrons, electrons and energy in the form of radiation to stabilize their nuclei.

However, radioactive substances are not able to emit protons, neutrons, electrons randomly, and the type and the number of particles emitted are unique to each substance. For example, 2 protons and neutrons, 1 electron, or a certain amount of energy are emitted by alpha, beta, and gamma rays, respectively.

As another example, radium and radon, which are naturally-occurring radioactive substances found in hot springs, are known to emit alpha rays.

Potassium, an element found in many foods, emits beta and gamma rays. Furthermore, radioactive cesium emits beta and gamma rays, while strontium emits beta rays.

Regardless of their sources, whether it is naturally occurring or artificial, all radioactive substances emit either alpha, beta, or gamma rays. The health effects of radiation are thus influenced by the amount of radiation exposure.

70. The intensity of radiation is measured to identify radioactive substances

All elements are collections of small particles called protons, neutrons, and electrons. The numbers of these particles in radioactive substances are unbalanced, and these substances become unstable and emit unneeded protons, neutrons, and electrons to stabilize their nuclei; each emission spectrum is unique to the element.

In addition, the intensity of the emitted energy (gamma ray) is also unique to each radioactive substance. In other words, a particular radioactive substance always produces exactly the same level of energy or gamma ray.

Food radiation monitoring and safety inspections are conducted utilizing this property.

By measuring the intensity of emitted gamma rays, food radiation detectors are able to separate the gamma rays produced by cesium-137 from those of potassium-40, which is a naturally occurring radioactive substance.

Radioactivity in food is interpreted as negative when potassium-40 is detected but cesium-137 is not.


The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on May 1st and 8th 2016 was reproduced for MRIC Global under the author's permission.

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