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According to information as of March 22 08:52 JST.
Professor Shunichi Yamashita
Graduate School of Biomedical Sciences, Nagasaki University
President, Japan Thyroid Association
Prof Yamashita has recently been requested by the Fukushima prefectural governor to be the area's nuclear radiation health risk management advisor.
About the initial evacuation
"During the first week, it was unfortunate that the quick succession of unpredicted events had made it difficult for everyone to share information. I first became aware of the seriousness of the situation when the government issued an evacuation warning that didn’t follow the usual standards. Normally people living within 10km of the site would be evacuated in the case of an emergency. People would first be asked to stay indoors, and then be given the order to evacuate if the radiation levels wouldn’t drop. In the current case, people living within 20km were evacuated, and then people living within 30km were told to stay indoors. It doesn’t make sense that people who had been evacuated to a safer area should be asked to stay indoors.
"The series of troubles at the reactor were unprecedented. Radiation continues to come out at an on-again, off-again basis. The type of radiation coming out varies, and so do the amounts. We need to continue monitoring the area and find out whether the 30km indoor evacuation order was necessary."
The effects of radioactive material as compared to the Chernobyl disaster
"Radioactive material has spread across a number of places. In a way though, radioactive materials emit what’s called a tracer, which is very easily detected and measured. The amounts that have been recorded so far will not have an effect on people’s health. If the extent of the Chernobyl nuclear disaster could be represented by Mount Pinatubo’s eruption in the Philippines, the incident at Fukushima would be represented by the Mount Unzen or Shinmoedake volcanic eruption. In either case, there’s a risk of getting burns or something more life threatening from the volcanic ash or lava, but moving away from the area lowers these chances. The only difference between the two is that Mt Pinatubo’s effect spread across the entire world, whereas Mt Unzen or Shinmoedake only affected a small area.
"Radioactive material coming out of Fukushima Daiichi is like ash spewing out of an erupting volcano. Moving away 20km will significantly lower its effects. The amount of radioactive material that has been released up to now is getting smaller and smaller as is the area over which it is being spread. A person who gets radioactive material on their skin can easily wash it off. It’s wrong to say that even a trace of exposure would be dangerous."
Currently, the chances of getting cancer are not rising
"Human bodies already contain about 1000 to 5000Bq of radioactive potassium. Taking a radon bath will obviously result in your body absorbing radon too. As long as the amount of these radioactive materials are small (10 – 500μSv) then there shouldn’t be a problem over a relatively short period of time.
"Right now iodine-131 levels in spinach and milk have gone over the standard limits, but it’s safe to eat it once or twice. The other thing is iodine-131 has a half-life of eight days so its effects will wear off quickly.
"Being exposed to 100mSv of radiation at once could raise the chances of getting cancer, but if the levels can be kept below 50mSv it should be alright. Radiation exposures considered safe for the nuclear power plant workers has been set to a total of 50mSv per year, and this is secure.
"People seem to be worried that radiation exposure will lead to cancer later on in life. But if we exposed 100 people to a 100mSv dose of radiation, only one or two people would have a chance of getting cancer (one in three Japanese people die from cancer). Thus, it’s unlikely more people will get cancer as a result of these events."
No need to worry about radiation exposure for general public
"In the area between 10 – 20km from the nuclear plant, those who have already been evacuated might have been exposed to about 1mSv of radiation. However, there is no difference between several micro-SV and 100mSV in terms of their effect in causing cancer.
"It should also be noted that the effect of radiation of exposure, 100 times of 1mSv and 100mSv at a time, is very different. The people we should be worrying about in regards to radiation exposure are those working at the site of Fukushima Daiichi nuclear power plant. We need to think about how to secure their health. Otherwise people do not need to worry about radiation exposure.
"It is argued that the effect of low-level radiation exposure on health conditions cannot be demonstrated. However, 'no evidence of no effect', does not necessarily mean we should worry about the effect. It is understandable that people fear the radiation exposure because it is invisible, but radiation can be measured in scientific ways. That is, we have a means to prevent harm from radiation. We should not panic. I would ask you to behave in a rational manner as a member of the society."
What’s next
"Radiation has spread across a wide area so it would be a problem if food is contaminated through the food chain and then sold at markets. We need to collect data about what areas have been contaminated in what ways, and be open with sharing this data. Using this information will help us to calculate radiation levels absorbed into our body within a year, and if the total annual intake is anywhere between a few tens of mSv to 100mSv, then regulations need to be put in place. I do think this will toughen Japan’s already strict food safety standards, but we need to pay particular attention to prevent negative rumours from spreading.
"Given the scale of the impact of this earthquake and its consequent tragedies, I argue that people in this nation should be prepared to help relieve the burden the people of Fukushima now face. It is now that we need to follow the example of the Japanese way and carry on in a harmonious and calm way as our ancestors have through history."
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