Authors: Karim Moutchou Institution: Medical Student, Fez Faculty of Medicine and Pharmacy Editor: Akihiko Ozaki, M.D., Yuki Senoo Students around the Arabic world are taught during high school geography classes that Japan is a unique East Asian country. At my school, the lessons about Japan always started and ended with the same sentences: “Japan is a country that faced and is still facing a lot of natural challenges. However, they are always overcoming these challenges and have grown powerful in their foreign relations.” The textbooks then explain in numbers the natural disasters that Japan has experienced every year, from earthquakes to massive tsunamis. After that subject, students are t

Author: Masaharu Tsubokura Editors: Akihiko Ozaki M.D., Yuki Senoo 121. Tritium’s Radiation Level is Very Low A radioactive substance called “tritium” often appears in articles covering the issues of contaminated water released from the nuclear plant. Tritium is not only an artificial substance that was released from the accident this time but also one naturally generated in our environment. As previous articles have explained, the health effects of radiation are determined by the extent of the exposure dose, not by whether their source is a natural or artificial radioactive substance. Tritium emits a very low level of radiation (beta rays), and its energy level is so small that plastic wrap

Author: Masaharu Tsubokura Editors: Akihiko Ozaki M.D., Yuki Senoo 119. Cesium is rarely found in water Cesium is usually tightly bound to soil particles and is hardly detected in water. When radioactive cesium is detected in water, it is generally due to mud floating at the surface that had accumulated at the bottom; almost no contamination has been found in water from ponds or dams. On the other hand, soil-bound radioactive cesium is sometimes present at the bottom of a pond or dam. However, most of this cesium is not from surroundings such as forests; the majority has been present in lakes since the early phase of the post-disaster period. When the water level of the pond is 1 meter, radi

Author: Masaharu Tsubokura Editors: Akihiko Ozaki M.D., Yuki Senoo 117. Cultivation leads to reduction of contamination When radioactive cesium is present in the soil, plants absorb it instead of nutrients, and this process results in contamination. Moreover, the extent of absorption of radioactive cesium could vary depending on the types of plants and the soil. On the other hand, numerous countermeasures and efforts have been made to reduce the level of contamination in agricultural products, including soil decontamination and redesigns of the cultivating method, fertilizer types, and growing plants. Cultivation and tillage are two of the approaches taken to reduce contamination. It has bee

Author: Masaharu Tsubokura Editors: Akihiko Ozaki M.D., Yuki Senoo 115. Soil bound cesium is not absorbed by plants When radioactive cesium is present in the ground, plants absorb it instead of nutrients, and this results in contamination. However, plants do not actively absorb cesium present in the soil. Most cesium is bound to soil particles or fully captured within soil particles, so plants cannot absorb it. For plants to absorb cesium, it must be dissolved in water; however, it has been found that cesium scarcely dissolves in water. Therefore, when cesium is detected in water, it is generally because the device is measuring the soil-bound cesium present in the water. Since plants are not

Author: Masaharu Tsubokura Editors: Akihiko Ozaki M.D., Yuki Senoo 113. Cesium is absorbed differently by each plant Plants grow by absorbing minerals and water from the soil through their roots. When radioactive cesium is present in the soil, the plant will absorb it along with nutrients, and this results in contamination. Previous investigations have revealed that the extent of contamination differs by plant type. In detail, the rate of absorbed radioactive cesium compared to that in the soil could vary from approximately 1/1000 to 1/10,000 depending on the type of plant (called the transfer coefficient). For example, leafy vegetables such as Japanese mustard spinach, spinach, potato, and