Ask Dr. Hallberg: The risks of radiation

Japan's prime minister says the situation at the Fukushima Daiichi nuclear complex remains unpredictable and the country remains "in a state of maximum alert."

Today, the U.S. Department of Energy announced it will ship radiation robots to help deal with the disaster because of the threat of radiation on the plant's employees.

Dr. Jon Hallberg, regular medical analyst for MPR's All Things Considered, and host Tom Crann discussed radiation issues.

Tom Crann: Give us the basic definition here. What is radiation?

Dr. Jon Hallberg: At its most basic, radiation is simply energy that's coming from one source and traveling through some material or through space. So, it's important to remember that light and heat and sound are all forms radiation. But what we're really talking about is ionizing radiation. You've got atoms that are unstable that are releasing energy. They're also known as radioactive materials.

Crann: In a situation like a nuclear plant, they're controlled strictly, ideally, but what happens when they're not controlled?

Hallberg: We can take advantage of the fact that they're unstable, that these atoms are trying to become stable and we can harness that. We can create heat, which in turn heats water and gives us power. But when we're exposed to radioactive materials, that energy can damage tissue. And if the exposure is limited, the cells have a chance to repair themselves. But the higher the exposure, the more damage occurs.

Crann: We often hear that radiation has a cumulative effect in the body over one's lifetime, is that true?

Hallberg: In the acute setting, depending on how much you are exposed to, you can have things that we've all heard about -- this acute radiation sickness. But sure, the more exposure you have, it can cause long-term damage that may not appear for years.

Crann: Then there's the acute radiation sickness that would cause things like nausea or much worse?

Hallberg: That's right, and the reason it does this is that you have tissues that are rapidly dividing, so the more rapidly dividing a tissue is -- skin, for example, the lining of our intestines and stomach, bone marrow producing blood cells -- that's exquisitely sensitive to radiation, and so that's why people feel nauseous. They'll have vomiting, they may have a drop in their blood count. That's all part of that acute radiation sickness phenomenon.

Crann: And radiation can be ingested through contaminated food and water, right? That's why we're hearing concerns about the food supply in Japan, correct?

Hallberg: That's right, and there's some concern that the food supply's been contaminated, and the minute you hear that, you think, 'OK, I simply cannot eat or drink any of this stuff.' But they've done some calculations, and based on the radiation levels that they're seeing, it would take huge amounts of consumption of some of these foods to actually cause a problem. So it's one thing to hear that it's contaminated; it's another thing to have it at such a level that it actually has an impact on human health.

Crann: We are hearing a lot about potassium iodide tablets and also that they distribute vouchers for them routinely around nuclear power plants. Why do they work?

Hallberg: All that they do is they try to prevent thyroid cancer at its simplest. The reason that's important is that the thyroid gland produces two thyroid hormones. These hormones have iodine in them, and the thyroid gland takes up iodine indiscriminately, whether it's contaminated or not. So by flooding yourself, by flooding the thyroid gland, with potassium iodide, which is available in a tablet form that's approved by the Food and Drug Administration, you can block the radioactive stuff from being taken up. And that hopefully prevents thyroid cancer down the road. But it doesn't prevent radioactive material, radioactive iodide from being absorbed in the body; it just simply prevents thyroid cancer.

Crann: Is it medically necessary for people to take these tablets as a preventative?

Hallberg: Only if it's been instructed by public health officials. In Japan that's one story. I know some people here who live near nuclear power plants have vouchers to have this, though most people have blown that off and not thought much about that. For most of us, it is simply not a concern. We don't need to be stockpiling it, we don't need to be taking it. I think we just need to be attentive and if there is ever a time where we need to take it, we'll be notified that that's the case.

(Interview transcribed by MPR reporter Elizabeth Dunbar.)

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