Dr. Tsubokura's Radiation Lecture Vol.141

Author: Masaharu Tsubokura M.D., PhD.

Editors: Akihiko Ozaki M.D.,PhD., Yuki Senoo MUDr.

281. The extent of the exposure dose determines the health effects of radiation

Over the last several months, we have discussed the current circumstances surrounding COVID-19 and its related health topics. With this week's article, I would like to return to the topic regarding radiation. I would like to look back at what I have introduced regarding the effects of radiation in past articles as a quick review of the crucial points to note.


The adverse health effects of radiation exposure include hair loss, bleeding disorders, diarrhea, and burns. However, these symptoms only occur when you are exposed to a significantly high level of radiation—more than a few hundred millisieverts—which can damage many cells at once. This is called a deterministic effect of radiation because it is determined to happen to those who received a threshold dose of radiation exposure.


This also means that the deterministic effect will not occur to anyone who has received radiation exposure below the threshold dose (about several hundred millisieverts). Thus, undergoing CT or X-rays will not cause diarrhea, burns, or hair loss.


The extent of the exposure dose determines the health effects of radiation. The level of radiation exposure we have been receiving in our daily lives due to the nuclear accident since the 2011 Fukushima Nuclear Power Plant Accident is an order of magnitude lower than the threshold dose, which is hundreds of millisieverts. Therefore, the deterministic effects of radiation, such as nosebleeds, diarrhea, burns, or hair loss, will not occur. The same is true even in areas where evacuation orders have recently been lifted.


282. Radiation sensitivity... different among organs

The adverse health effects of radiation exposure include a bleeding disorder (difficulty in stopping bleeding) and diarrhea. These health effects from radiation are called deterministic effects of radiation as it is determined to happen to those who received a significantly high dose of radiation exposure.


Some of you may wonder why specific symptoms appear after being exposed to high-levels of radiation, among many other health manifestations. This is because the susceptibility to radiation is different depending on organs.


From the previous research, it is known that actively dividing and immature cells are more susceptible to radiation exposure. For example, the bone marrow, which works like a factory producing blood cells, is constantly dividing to make cells all the time. These precursor cells that later develop into blood cells are easily affected by radiation, and exposure to high doses of radiation causes insufficient blood supply.

 

As another example, the surface cells of the digestive tract, which absorb water and nutrients, are also susceptible to radiation exposure. This is because since they are metabolically active, these cells are constantly replaced by new cells at a rapid rate. On the other hand, nerve and muscular tissues, which do not undergo cell division in adulthood, are known to be resistant to radiation.


Nevertheless, the air dose rate of additional radiation exposure we may receive from the 2011 Fukushima Daiichi Nuclear Accident is an order of magnitude lower than the level of radiation exposure which can cause these adverse health effects—hundreds of millisieverts. Therefore, we will not experience the deterministic effects of radiation in our daily lives.