Radiation Q&A
Radiation knowledge FAQ for surviving
after the Fukushima nuclear power plant disaster
In response to the first nuclear power plant disaster of Fukushima,
I consider questions many of which you have probably thought of in a Q&A form.
The actual condition of radioactive contamination
Q. What kind of radioactive substances were scattered by this accident?
A. Radioactive iodine, cesium, and strontium which the breaking down of uranium in a nuclear reactor creates are the main substances.
Q. Iodine and cesium are often heard of in the news. However, why do we seldom hear about strontium?
A. The most commonly measured type of radiation is gamma rays. But strontium is difficult to analyze because it doesn't emit gamma rays. Therefore, test results come out much later.
Q. How and when did the radioactivity spread?
A. On March 15, 2011, at the first, it flowed into a large area including Fukushima prefecture and the north Kanto region. At this time, in the areas where snow or rain fell, much radioactive cesium remained in the ground and continued emiftiny high levels of radiation in every area. This is the reason a radiation measurement value from under the drainspout of a house or the side of a road is high. Also, a plume passed along the Ibaraki coast and traveled into Miyagi and Iwate in additim to besides southem Kanto from the evening of the 20th to predawn on the 22nd. Since it was also raining at this time, the contamination spread.
Ｑ. How far did the contamination spread from influence of this accident?
A. The number of communities in which the annual dose of radioactivity exceeded national safety standords of more than a 1-mm sievert in trial calculations conducted by the Ministry of the Environment, were8 cities and prefectures (Miyagi, Fukushima, Ibaraki, Tochigi, Gamma, Saitama, Chiba, Tokyo).This amounts to 11,600 square kilometers.
Q. Are other areas OK?
A. As of November 17, 2011, although trial calculations had not been fully carried out yet, if the contamination map which the Ministry of Education, Culture, Sports, Science and Technology released on November 11 is examined the possibility that areas exceeding 1-mm sievert per year is include southern Iwate, southern Niigata, and eastern Nagano is high.
Q. What is influence on food?
A. In the area where the cumulative dosage in soil is high on the contamination map, foods exceeding safety standards exist. The standards were exceeded by several foods, such as raw milk and spinach, in Fukushima at the beginning of the accident. Even in Nagano, radioactive cesium exceeding safety standards was detected in the wild mushrooms in the border region between it and Gamma prefectures border between prefectures in October. On the other hand, contamination has been in very little vice but there is a difference between types of food.
Influence on health
Q. Why is it said that radiation is bad for the body?
A. Radiation may break the DNA’s genes of cells in the human body. But a cell is not defenseless, either, and if the damage is small, changes caused in the genes may be restorable. Restored cells continue to live. However, occasionally mistakes is made in the repair and the information of the gene deteriorates. This is called mutation. Mutation may cause future cancer in a contaminated person or hereditary diseases in childen it in the future. But this is only a possibility to the only and may not occur at all. Theory the smaller the theoretical, the amount of radiation the lower probability of this accvring, but of course probability becomes higher if much radiation is absorbed.
Q. What is the difference of contamination in a child and an adult?
A. If contaminated during the time when internal organs are being built, it will be easy to generate cancer. It is thought that the risk of cancer in a 10 year old person is two to there times higher than a 30 year old adult.
Q. In case of exposure, how much radiation is dangerous?
A. From investigation of A-bomb victims in Hiroshima and Nagasaki, in proportion to a dose of radioactivity after contamination of more than 100-mm sieverts, the risk of deadly cancer goes up and it rises by 0.5% on average across all age groups perah 100-mm sieverts. As for contamination below 100-mm sieverts, the data is strong that tisks are minimally statistically, and the precise influence on health is unknown. According to the "precautionary principle" used by the International Commission on Radiological Protection to protect people's health, the hypothesis is that below 100-mm sieverts has a risk according to a dose has been adopted.
Q. How much was the dose of radioactivity emitted by the disaster at Reactorl at the Fukushima nuclear power plant?
A. The dose of radioactivity for the rast majority of residents both in and outside of Fukushima is to have been regarded below the 100-mm sievert level.
For reducing contamination
Q. What should we do in order to protect ourselves from radiation?
A. For example, radioactive potassium is contained in food which we eat at a much higher level than cesium.Therefore, much food will be lost if we try to avoid all radioactive material. However, it is a general rule that the lowest dose possible is best. This radioactive contamination is unnatural contamination and, so to speak, is environmental pollution. It is rational to try to avoid it.
Q. What should we do to reduce contamination in everyday life?
A. In the area distant from the first nuclear power plant at Fukushima, even if one does nothing, there are many specialists who think that there is no influence on health. If you are worried, try to measure the dose around your a house with dosimeter, and decontaminate the area. Japanese Society of Radiation Safety Management has release a decontamination manual for people residence.(http://www.jrsm.jp/) Moreover, it is not necessary to throw away the clothes worn during decontamination activities, because 80 percent or more of the radioactive materials absorbed into the clothing can be removed with proper washing. Moreover, it is no problem to wear cloth hung out in an area exceeding 1-mm sievert because the dose of radioactivity is about 1/10,000 of 1 mm sievert within people's annual yearly limit. In addition, when rubbing a paved road polluted with cesium with a wire brush, 90 percent or more can be decontaminated.
Q. What are some ways for reduce the influence radioactivity in Fukushima?
A. We need to take the following precautions.
・After working outdoors, wash your hands, and a face, and gargle.
・If dirt or sand goes into your mouth, gargle well.
・In the case of infants, refrain from using a sandbox.
・It is safer to open an umbrella if it will be rainy.
・Mud on shoes should removed as much as possible when going to school and going home.
・When there are dust clouds, shut the windows.
Q. I still feel very uneasy...
A. We can't show any absolute criteria of safety because even a little radiation has some risk. So, we should decide the amount of risk we can accept deal with in our daily life. Maybe, this need to make our own decision is a major factor in our uneasiness.