Dr. Tsubokura's Radiation Lecture Vol.4

Author: Masaharu Tsubokura

Editors: Izumi Yoshida, Mariko Irie, Yuki Senoo

7. The high radiation level of radon in European countries

　The air contains the radioactive substance called radon. In our daily life, we breathe in air containing radon.As the words "radon hot springs" indicate, hot spring areas also contain radon as well. Radon is a gas generated from natural uranium in the soil, and it outputs alpha radiation as well as plutonium.By inhaling the radon, our lungs are exposed to radiation.The concentration of radon in the air varies from place to place. The exposure in European countries is higher, around 2 millisieverts per year in Germany and 3 millisieverts in France, and relatively low in Japan, around 0.3 millisieverts.Merely speaking only of the level, even if the total radiation exposure in a year increased by 1 millisievert due to the nuclear accident, the exposure dose will be still lower than in Europe.

8. The radiation dose depends on the type of soil

　The soil contains radioactive substances. Because the level of radioactive substances differs depending on the type of soil, radiation dose also varies depending on the location. Granite rocks and marble contain a lot of radioactive substances; therefore, countries with stone buildings or many cobblestones have high radiation doses.There are variations in radiation dose in Japan as well: It is higher in the west than in the east in general, and the Tohoku region is originally low. Therefore, the annual radiation dose received from the soil has a difference of about 1 millisievert in Japan. Gifu was said to be the highest by prefecture. The lowest was Kanagawa, and Hiroshima is also known to be somewhat higher; however, this is not the influence of the atomic bomb in WWII. It is due to radioactive substances in the soil containing the granite mentioned above. Lastly, Nagasaki is lower than the average of Japan. ---------------------------------------------------------------------------------------------------------------------------------------The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on February 22 and March, 1st 2015,and was reproduced for MRIC Global under the author's permission.