How dangerous are low doses of exposure to radioactivity to humans? This question is heatedly debated within the scientific community. But it is not an easy time to convey details of that debate to the people in Japan living near the Fukushima nuclear plant who have now been exposed to the dangers of radiation.
Radiation-protection specialist Shunichi Yamashita, 59, has made significant contributions to what is known about the effects of radioactive radiation. He has studied the survivors of the World War II atomic bombing of Nagasaki as well as the consequences of the 1986 reactor accident at Chernobyl, which he has visited nearly 100 times as part of a Japanese scientific envoy. He is currently researching the effects of the Fukushima catastrophe -- though his efforts are meeting with much resistance from local residents.
SPIEGEL interviewed Yamashita about the expected effects of exposure in Fukushima and his plans to conduct one of the largest scientific studies even undertaken in the region. As part of the study, he hopes to examine the health effects of the nuclear disaster on some 2 million people.
SPIEGEL: The government of the Fukushima prefecture has invited you to inform people in the affected region about radiation risks. Right at the beginning, you said: "The effects of radiation do not come to people who are happy and laughing, they come to people who are weak-spirited." What did you mean by that?
Yamashita: That was on March 20 during the first meeting. I was really shocked. The people were so serious, nobody laughed at all.
SPIEGEL: These people's villages and home towns are contaminated. Nobody knows about the invisible dangers. What did you expect?
Yamashita: The mood of the people was really depressed. From animal experiments with rats we clearly know that animals who are very susceptible to stress will be more affected by radiation. Stress is not good at all for people who are subjected to radiation. Besides, mental-state stress also supresses the immune system and therefore may promote some cancer and non-cancer diseases. That is why I told people that they also have to relax.
SPIEGEL: And to help people relax, you also said that doses of 100 millisievert per year would be fine? This is normally the limit for nuclear power plant workers in emergency conditions.
Yamashita: I did not say that 100 millisievert is fine and no reason to worry. I just said that below that threshold we cannot prove a higher risk for cancer. That is the evidence from research in Hiroshima, Nagasaki and Chernobyl.
SPIEGEL: But you didn't understand that your reassurances would make people even more angry and frightened?
Yamashita: I think it really contributed to the confusion that the Japanese government decided to set the standard for yearly maximal dose at 20 millisievert. The International Commission on Radiological Protection suggests a limit between 20 and 100 millisievert in a situation with a nuclear emergency. Which threshold you pick is a political decision. You must weigh the risks and benefits, because any evacuation will also have risks. The Japanese government chose the most careful radiological approach. That made people more confused and insecure.
SPIEGEL: Your comments have made you a controversial figure. A Japanese journalist wants to sue you. Anti-nuclear activists ...
Yamashita: ... they are not scientists, they are not doctors, they are not radiation specialists. They do not know the international standards, which researchers worked on very hard. It makes me sad that people believe gossip, magazines and even Twitter.
SPIEGEL: Why should the people trust experts who have been telling them for decades that nuclear power plants are 100-percent safe?
Yamashita: I was surprised when I arrived in Fukushima that nobody was prepared for such a disaster. I used to advise China and states of the former Soviet Union on radiation protection. Now we have a tremendous accident in my own country and are not prepared. People in Fukushima did not even know that there are 11 reactors in their region. The medical faculty of the University of Fukushima didn't have a single specialist in radioprotection medicine.
SPIEGEL: Would you address the people affected by the accident in a different manner today?
Yamashita: In a situation where people had no understanding of radioactivity at all, I wanted to be very clear. I have now changed my communications approach from black-and-white to gray scale.
SPIEGEL: People want clear answers. Where is it safe? And where is it not?
Yamashita: We don't have those answers. When people ask me: "Are doses below 100 millisievert 100 percent safe?" Then I have to answer as a scientist: "I don't know."
SPIEGEL: From previous studies we have learned that if 100 people are exposed to levels of 100 millisievert, statistically speaking, one person will get cancer because of the radiation. Is it possible to project the level of danger of lower doses?
Yamashita: That could be. The problem is that to estimate the risk for disease we use the so-called linear-nonthreshold dose-response model, which assumes that even a small additional radiation dose would cause a small increase in cancer incidence in an exposed population. Such an increase is theoretically measurable, but with the doses below 100 millisievert it is statistically insignificant and thus cannot be considered as an argument in support of excessive risk. Also, with a tumor we do not know what caused it. Radiation does not leave a diagnosable signature. From radiation biology we also know that smaller doses can damage human DNA. But the human body can effectively repair those injuries within a short time; this is a natural intrinsic protective mechanism. That is what I am trying to tell the people.
SPIEGEL: And what should people do with this kind of information?
Yamashita: With low radiation doses the people have to decide for themselves whether to stay or to leave. Nobody can make that decision for them. They have to weigh the risks and benefits: Moving can mean a loss of jobs and having to change schools for the children. These factors cause stress. On the other hand, this family might be able to avoid the risk of cancer, even if it is only minimal.
SPIEGEL: That families affected by the nuclear accident are being forced to make any such decision is a terrible burden.
Yamashita: Yes. Therefore Tepco and the Japanese government should support people in their decisions. They should support those who want to stay as well as those who think even more than one millisievert is too high.
SPIEGEL: What kind of health risk from the radiation will the people around the plant in Fukushima have to face?
Yamashita: I do not think there will be any direct effect of the radiation for the population. The doses are too small.
SPIEGEL: So you don't think there will be any cases of cancer or cancer deaths?
Yamashita: Based on the data, we have to assume that. Of course, the situation is different for the workers in the plant.
SPIEGEL: Now you are already talking about something you actually intend to research. You plan to monitor the health condition of the residents of Fukushima for the next 30 years.
Yamashita: In the current situation, it is very difficult for us to be accepted by the local residents. We have to make the best medical care possible for these people the first priority.
SPIEGEL: Do you think adopting a more understanding tone than you have up until now would help you to gain acceptance?
Yamashita: Because of the accident, Tepco and the Japanese government have lost the trust of the people in Fukushima completely. The people are suffering, not only because of the earthquake and the tsunami, but also from severe radiation anxiety, real radiophobia. Therefore we have to lower the anxiety (and) give them some emotional support. And, later, we can open the discussion about epidemiological studies. Without the support of the local people, we cannot do anything. In this situation it doesn't even help that I am the expert from Nagasaki and Chernobyl. This is why I moved to Fukushima.
SPIEGEL: Who do you want to examine in your study?
Yamashita: There are three groups. The workers, the children and the general population. The workers are exposed to high-dose radiation. We surely need to monitor them to follow the effects concerning cancer and other diseases. The general population would be divided into two groups: One that was exposed to relatively low radiation and one that was exposed to relatively high radiation. The Fukushima government health office is just finishing a pilot study with which they have questioned 26,000 people.
SPIEGEL: But the people don't know how much radiation they were exposed to.
Yamashita: That is what we have to find out. We ask where the people were on March 11 at what time and then we ask those questions for every day in March. We also ask what people ate the first two weeks after the accident, what material their house or apartment is built out of. We want to connect these data with information of the distribution of the radioactive cloud and calculate the dose after the fact.
SPIEGEL: How many people should participate?
Yamashita: All 2 million residents of Fukushima prefecture. It is a big task and would set a science record. The government just decided about compensation payments for people affected by the nuclear accident. Through such applications we want to try to contact also those who moved outside of Fukushima.
SPIEGEL: What about the children?
Yamashita: We want to test the thyroids of all children under 18, altogeher 360,000 children, with ultrasound. After exposure to radiation it takes about five years until thyroid cancer first develops. We know that from Chernobyl.
SPIEGEL: Are you also researching the mental effects of the disaster?
Yamashita: Of course. We know from Chernobyl that the psychological consequences are enormous. Life expectancy of the evacuees dropped from 65 to 58 years -- not because of cancer, but because of depression, alcoholism and suicide. Relocation is not easy, the stress is very big. We must not only track those problems, but also treat them. Otherwise people will feel they are just guinea pigs in our research.