How Will Japan’s Nuclear Accident Effect Global Cancer Risk?

MD Anderson Cancer Center
Date: 05/20/2011

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Lisa Garvin: Welcome to Cancer Newsline, a weekly podcast series from the University of Texas and the Anderson Cancer Center. Cancer Newline helps you stay current with the news on cancer research, diagnosis, treatment and prevention providing the latest information on reducing your family's cancer risk. I'm your host Lisa Garvin. Today, our topic is the effects of the radiation situation in Japan. And here to talk about that is Professor James Cox who is in the division of Radiation Oncology here at MD Anderson. Welcome to you, Dr. Cox.

Dr. James Cox: Thank you. I'm happy to be here.

Lisa Garvin: Let's talk about radiation sickness as a whole. What happens when people are exposed to high amounts of radiation such as the plant workers at Fukushima Daiichi plant?

Dr. James Cox: The plant workers at Fukushima Daiichi plant probably are not getting sick. It's a little hard to say but they are being monitored very closely so that they get levels of exposure that would carry some risk long term arguably in terms of cancer risk but not risk of harming their health at the moment.

Lisa Garvin: And let's talk about--I think we have to talk about Chernobyl because as earlier when we were talking--Chernobyl was an explosion so the effects of the radiation were much more acute that in Japan, correct?

Dr. James Cox: Yes. They were much more devastating than in Japan. And many more people were exposed and people did die of radiation effects there. The workers who were obligated to go into those plants, into that region probably were exposed to high enough levels that they died of gastrointestinal effects, effects mostly on the bone marrow and those are the most immediate, most urgent effects of very high dose, very high dose. The only experience that we really have for that are accidents in reactor sites years ago and of course the experiences of the atomic bombs in Hiroshima and Nagasaki.

Lisa Garvin: In some of the research I have done that people even though they maybe exposed to more radiation they might not die from it as others who have been exposed to less radiation have passed on. So it's kind of hard to get a handle on really what the line for the fatal dose I guess.

Dr. James Cox: Well, the current thinking is that the risks of short-term effects as well as long term effects are closely related to the dose receive. So people who get very low doses have a low risk. People who get very high doses have a much higher risk. But most of the risk that we're talking about is risk of long-term effects, mostly theoretical risk of developing cancer, not illness to individual himself or herself.

Lisa Garvin: So let's talk about, let's talk about ground zero in Japan and the workers at the Fukushima Daiichi plant that are trying to, you know, contain the core. What theoretically could they expect down the line?

Dr. James Cox:They would be at a statistically significantly greater risk for developing cancer, that risk is not as high as many people think. Even the people who were exposed to the bombs in Hiroshima and Nagasaki have had increased risk relative to those who were not exposed. But the risk is not nearly as great as people think. Fewer than 1000 cases of cancer have occurred above what would be expected in the population in general and that's 120 or 140,000 people who were exposed to the atomic bomb.

Lisa Garvin: So as we move out from the Daiichi plant what are the effects as moved out? Obviously, they're worried about their food supply, water supply. What sort of effects would we see there?

Dr. James Cox: The major concerns are about fallout that has contaminated the food and the water. And the food of course is eaten by the animals especially cattle and so they're worried about contamination of the meat of the animals in the area. And especially milk from cattle because we know from the Chernobyl experience that the radioactive iodine I-31 that was on the grass eaten by the cattle concentrated in the milk and then drank by the children. That was the single most problematic risk for the population around Chernobyl. And a lot of those children developed cancer of the thyroid. And not--there were very few of them that died because cancer of the thyroid is a very treatable form of cancer but nonetheless there were lots that develop it.

Lisa Garvin: Now, does this linger in the body in some form? How does radiation? Does it stay in the fat cells or how does that work?

Dr. James Cox: Well, radioactive iodine is concentrated in the thyroid. Iodine normally is concentrated in the thyroid and radioactive iodine would be picked up just as any iodine would and concentrated in the thyroid. It can be prevented if people know it's happened or right after it's happened by taking potassium iodide and flooding the thyroid with normal iodine so that there's no room for the radioactive iodine to get into the thyroid. The I-131 has a half life of only 8 days and so in 80 days it's gone. It doesn't have any effect. It's just iodine. So there is very little long-term risk except for the sequence of events that I said with the grass and the cattle and the milk and the children.

Lisa Garvin: How long would it take for the radiation to disappear from the food chain?

Dr. James Cox: Well, for iodine it's gonna be gone within a couple of months. There are other isotopes though. They get picked up in cabbage, in lettuce, leafy vegetables such as caesium. And radioactive caesium, cesium-137 has a half life of 30 years. So it's a potential risk for a long period of time. All of this is diluted in the environment relatively quickly. So what was in the air has been diluted very quickly as you can imagine in any particular matter. Smoke goes into the air. What is in the sea? The same thing. You've got an enormous potential bathtub if you will and the sea for the radioactive materials to be dispersed and so it's only quite close to Fukushima where there would be any--any risk. They have measured increased levels of radioactive iodine in the water in Tokyo once. It's just one time and then it went back to normal. Now, radioactivity is around us all the time and there are radioactive elements in the water and at foods and everything that we deal with. So it's not a matter of going to zero with radioactivity, that will never happen. It cannot happen. But it's a matter of having an exposure level that is sufficiently low that it's not considered to carry any risk.

Lisa Garvin: What about the fallout? I think, you know, in the days after the issue in the tsunami and earthquake in Japan, people in California were running out and buying iodide pills. I mean, what can we truly expect from fallout? How far would it go?

Dr. James Cox: If you can imagine smoke rising from a plant in Japan it's dispersed in the vastness of the air in the sky and it really poses no risk by the time it gets to the United States or Korea or China or a reasonable distance away. It's not a risk for people living in Tokyo. So it has to be taken in context that although higher than normal levels of radioactivity can be measured, they're not of a level that poses health risk.

Lisa Garvin: And what about research that we've done? You know we have a fairly small population of people who have been exposed to very high levels of radiation, your wife being one of them, what sort of research have we done about the long-term effects of radiation exposure?

Dr. James Cox: Almost all of that research has been done under the auspices of the originally called the Atomic Bomb Casualty Commission and then in 1975 it was renamed Radiation Effects Research Foundation. And that organization and the physicians and scientists working with it are following all of the people who were exposed to the atomic bombs in Hiroshima and Nagasaki. 40 percent, roughly 40 percent of the people who were exposed are still alive and so they have a long time to follow them, and they're looking at everything. They're looking at cancer risk and they have seen--they've seen an increased in the risk of cancer. They saw an increase in the risk of leukemia in their very first years and that risk has sort of dissipated. And now they are seeing risk of other types of cancer and it's continuing to go up and will go up. It's estimated probably to peak sometime between 2015 and 2020. They've looked at genetic effects. Surprisingly, there have been none even though we've seen the genetic effects in food flies, we've seen it in mice. We have not seen it in men. They've looked at the second generation, the offspring of the people exposed to the bomb. They've looked for genetic effects. They have looked for other health effects. They haven't seen it. So it's really the people who were exposed close to the bomb. And as distance from that site occurs the people who were exposed farher away are at much less risk. So it's really a dose related phenomenon that the people closest are at highest risk, people far away are at low risk. How low does the risk become? That's a scientific question of considerable interest but we don't have a lot of data.

Lisa Garvin: Well, what about the workers at Fukushima Daiichi? What sort of screening or follow-up programs should they be going through, you know, through the rest of their lives?

Dr. James Cox: As I understand it, and this is evolving just over the course for the last week, the workers at the Fukushima Daiichi plant were not confined just to regular radiation workers. They realized that those people got too higher dose too quickly and they had to be rotated off the responsibility of trying to work in the plant. They hired people from all over. They hired people, if you will, off the street who are willing to do this work and they monitored them very closely. And once they reached a certain level that was considered the maximum permissible dose for a radiation worker, they rotated them off and a new group came in. So the number is larger because they've tried to keep the exposure rate to what is understood and considered acceptable.

Lisa Garvin: Should there be certain screenings done like certain cancer screenings be done for these people?

Dr. James Cox: I learned within just the last day that there has been a relationship established between the universities around Fukushima and other major universities in Japan and the Radiation Effects Research Foundation to follow through with these people to monitor them long term. Now, how that does gonna take place? I don't know. I will go to Hiroshima in June because I'm one of the three this dean [phonetic] American directors of the Radiation Effects Research Foundation so I'll go to the annual meeting there and I'll know a lot more after that time. But I do know that they have established a relationship so that the work that is done by the RERF will be carried forward on behalf of this people who are exposed near the reactors in Fukushima.

Lisa Garvin: So in closing as Americans we really don't have to worry too much about either fallout or you know food stuffs and other things from Japan.

Dr. James Cox: You put it in perspective, if you lived in certain parts of China or Brazil or if you flew roundtrip from Houston to Tokyo, you would get very much exposure than you'll ever get from any of the fallout from Japan.

Lisa Garvin: Simple enough. Thank you very much Dr. Cox. If you have questions about anything you heard today on Cancer Newsline, contact Ask M. D. Anderson at 1-877-MDA-6789 [background music] or online at www.mdanderson.org/s. Thank you for listening to this episode of Cancer Newsline. Tune in next week for the next podcast in our series.

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