Fears have yet to settle over the radioactive substances scattered by the accident that started in March last year at the Fukushima No. 1 nuclear power plant.
The municipal general hospital in Minami-Soma, Fukushima Prefecture, located 23 kilometers from the crippled plant, continues to test the city’s 70,000 residents for internal exposure to radioactive substances. So far, 10,000 people have been checked.
Masaharu Tsubokura, a 30-year-old physician, has been working on the testing program since July 2011. He says radiation levels appear to be going down, but it is too early to specify a level where people are safe.
And citing the Chernobyl disaster, Tsubokura says food testing in Japan should be rigorous to prevent internal radiation exposure levels from rising.
Excerpts from the interview with The Asahi Shimbun follow:
* * *
Question: Is there anything particularly difficult about testing for internal exposure?
Tsubokura: We use a machine called a whole-body counter. We installed the latest model last fall. It takes two minutes to check a standing person, and the readings are very precise.
Minami-Soma municipal general hospital started testing last July. We had families from areas with the highest radiation levels come first. In the beginning, we took readings for four or five families a day, but now we're testing 110 people daily.
Minami-Soma's population was 70,000 at the time of the disaster. Now there are only over 40,000, but we have a plan to contact people who've left the city and test all 70,000.
Q: What are you measuring?
A: The amount of radiation in the body. There are many kinds of radioactive materials, but considering that this testing will be continuous, we are measuring cesium-137 because its half life is 30 years. Iodine, which is said to cause thyroid cancer, has a short half life of eight days. When we started taking readings, we couldn't detect levels of its presence.
We cannot rule out that people exposed to high levels of cesium were also exposed to iodine, so we are also closely monitoring the thyroid glands in our testing.
Q: What have you learned so far?
A: We have analyzed the results of around 5,000 of the 10,000 people we measured up until the end of last year with the new machine. We found that many of them have declining levels of radiation exposure.
Q: Well, the levels will decline with time, right?
A: As we have continued with the testing, we have confirmed that people's doses of cesium are decreasing because they are excreting it from their bodies. It takes an adult 100 days to reduce the amount by half and a young elementary student around 30 days. Children are quick to get rid of it.
So if we detect a certain level of cesium in a child, we can speculate that the child either took in higher levels of cesium at the time of the disaster (than an adult with the same level of cesium did) or ingested contaminated food soon before the testing.
Q: Is there a level at which a person can stop worrying?
A: There's no certain figure for that. For the moment, I'm considering a level of at least 20 becquerels per kilogram of body weight in adults and 10 becquerels in children as yardsticks for retesting. We are now retesting in the order of radiation levels detected.
For senior high schoolers and up, 3.6 percent had readings of 20 becquerels or higher. Of those, 16, or 0.3 percent of the total, measured 50 or more.
Q: How about the children?
A: Looking at around 600 junior high schoolers and younger kids, 11.92 percent had 10 becquerels or more, 0.69 percent had 20 or more, 0.17 percent had 30 or more, and none had 40 or more.
The average was 7.2 becquerels per kilogram. This figure is far lower than the levels reported after the Chernobyl accident.
We have found that the figures for internal exposure are lower with people in Minami-Soma than with people around Chernobyl living on soil with same levels of contamination as Minami-Soma.
A: Many people around Chernobyl continued to eat contaminated mushrooms they gathered in the forest or wild fruit they picked. But we have advanced goods distribution networks in Japan that will allow people to avoid foodstuffs from contaminated areas, and many parents gathered information to minimize their and their children's internal radiation exposure.
Q: Are you saying the readings so far don't warrant caution?
A: We are also seeking an answer to that question. According to International Commission on Radiological Protection (ICRP) guidelines to prevent radiation hazards, such levels would not pose risks.
However, we haven't had much experience with internal radiation exposure to begin with. We need a sufficient amount of medically reliable data to conclude, "This level is not a problem." That's why we can't explain what level is safe or dangerous.
Plus, although the readings from our scans are declining, the pace of decrease varies according to the individual. We can't come to a conclusion from just one reading. We have to measure on a continuous basis. Even if some people's radiation doses fall below the criteria for retesting, I'd still like to retest them if I have the chance.
Q: It seems we can't pin down the point where we can feel at ease.
A: So long as we don't know, the only thing we can do is take reasonable steps in our daily lives to reduce our risk to internal exposure. That's why we ask people what they were doing when the nuclear accident happened, what they ate, what sort of lifestyle they had and about their family members. Then we look at the results of their readings and discuss with them about what to do next.
Q: What are your suggestions?
A: Studies of internal exposure in Belarus, which was hit hard by Chernobyl, found that 94 percent was caused by food and the rest by air and water. In Japan, the ratios may be relatively lower for food contamination and a little higher for air and water. Still, we need to be careful about food.
Now with sufficient amount of test results, we can say to somebody, "Your exposure is at this level so you have to pay attention not to raise it." My impression is that people who are not mindful of what they eat and eat whatever they cultivate have high readings. People whose readings are slow to fall may have had contaminated food after the disaster.
Q: How do people react to their test results?
A: The majority take it calmly. At first, we often talked about things in black-and-white terms, like, "Have I been exposed or not?" And our explanations weren't very good because it was a novel experience to measure people's internal radiation exposure.
In the middle of the testing program, we decided to place priority on the testing itself. We inform people of the results through the mail and have them make an appointment to hear our explanation. Then, in the interviews, I started to notice people who say: "I'll die if radiation gets inside my body, right? What are they going to do about it?"
Perhaps their anxiety grew greater and greater while they waited before they heard our explanation. They won't listen to us. In addition, this is a municipal hospital, so many people think our testing is based on national or prefectural policy.
Some accused us of not having tested in April or May last year. Others voiced their suspicion that we didn't measure sooner because we were in cahoots with the national government. I ended up having arguments with them. The truth is that, we, too, wanted to check their radiation levels sooner, but we could not.
Q: So you started radiation checks through trial and error?
A: We didn't even have a testing machine at first, and my specialty is blood. We got the whole-body counter at the end of June, but we didn't know how to use it. I measured some hospital employees' exposure and detected radiation. I fretted about how to tell them the results. Many people at the time thought that even if only one particle of a radioactive substance enters their body, their life is in great danger. Everybody, including the hospital director, discussed how to tell the test results to people.
In the end, we found out that if we provide clear explanations as in a normal treatment, it'll work out.
Q: How did you get involved in Minami-Soma in the first place?
A: It started last April, when I visited the city after hearing that they didn't have enough doctors. Since then, I've been commuting to Minami-Soma each week, from Monday to Wednesday, and the rest I go to the Institute of Medical Science at the University of Tokyo.
Last May, when I was asked to conduct health checks and provide consultations regarding radiation exposure in the village of Iitate, I was surprised that many people had worsening chronic conditions, such as high blood pressure. There were no acute symptoms that appeared to be caused by radiation. They had a lot of stress from being unable to continue with their normal lives such as working on a farm or whatever.
Q: Doesn't being more careful about one's eating habits also cause stress?
A: Even so, they need to have their internal exposure examined over the long term. In Ukraine's case, internal exposure levels kept declining from the time of the accident in 1986 onward, but they began to rise in many areas from 1994. In some places, the level at which they peaked in 1998 was higher than in 1986. It's apparently because regulations on food were eased. The Ukrainian government once again tightened their regulations and even more than 25 years after the accident, they've maintained their inspection system.
Q: Japan also introduced tougher food standards in April.
A: What makes the standards meaningful is how rigorously the testing is conducted. No matter how strict you set the standards, contaminated food will slip through the cracks and be eaten if testing is carried out inadequately.
Test results in Minami-Soma suggest that some people, rather than eating contaminated food on a regular basis, may have eaten something that's highly contaminated by chance. In Ukraine, they test all the markets every day. We need to do that in Japan, too.
Q: In your view, food testing is crucial.
A: In addition, testing for internal radiation exposure like one in Minami-Soma, is also crucial. Radioactive substances have no color, taste or smell. I think there are many people feeling uneasy over unwittingly ingesting them in the course of their everyday lives. Taking a test is a chance to find out whether your current lifestyle is appropriate and whether there's anything you should change.
We should make arrangements to conduct internal exposure tests as well as food inspections to keep people from eating contaminated foods. I'd like internal radiation exposure tests to be part of regular health checkups.
* * *
Masaharu Tsubokura is a physician at the University of Tokyo's Institute of Medical Science. He was born in 1982 and graduated from the University of Tokyo's Faculty of Medicine. He served as an assistant at the Department of Hematology at Teikyo University and became a doctor at the University of Tokyo's Institute of Medical Science in April 2011. He also works as a part-time doctor at the Minami-Soma municipal general hospital.
- « Prev
- Next »