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STEVE INSKEEP, host:

It's MORNING EDITION from NPR News. I'm Steve Inskeep.

RENEE MONTAGNE, host:

And I'm Renee Montagne.

We've heard about radiation from the damaged nuclear reactors in Japan reaching American shores. Experts say so far there is no reason to worry and point out that we encounter radiation every day.

To find out more, we reached Peter Caracappa. He's a radiation safety officer and professor of nuclear engineering at Rensselaer Polytechnic Institute in Troy, New York. Welcome to the program.

Dr. PETER CARACAPPA (Rensselaer Polytechnic Institute): Hello. Thank you.

MONTAGNE: How many things emit radiation?

Dr. CARACAPPA: Well, radiation and radioactive material is kind of a part of nature. So everything that's living has some amount of radiation coming from it, a very small amount. Plus, there's radiation in the ground and the air.

MONTAGNE: Well, in other words, so the extremes are uranium in the soil to bananas?

Dr. CARACAPPA: Yes.

MONTAGNE: By the way, where do bananas get - what's their radiation?

Dr. CARACAPPA: So it's an isotope of potassium. Bananas have a lot of potassium. And a small amount of potassium naturally is called potassium 40, which is radioactive.

MONTAGNE: So there's radiation that could be dangerous and then there's the radiation that what?

Dr. CARACAPPA: Well, the term radiation can apply to a lot of different things. When we, you know, when you think about radiation, you think about what we call ionizing radiation or radiation that has enough energy that it has the ability to make chemical changes in material.

The broader definition of radiation includes a lot of things that we call non-ionizing radiation. That includes everything like radio waves and visible light and your microwave.

MONTAGNE: Right. So the radiation we could be and should be concerned about is ionizing radiation.

Dr. CARACAPPA: Ionizing radiation. Yeah.

MONTAGNE: Commonly we might get that from, say, an x-ray.

Dr. CARACAPPA: X-rays are also ionizing radiation. Yes.

MONTAGNE: And it's the sort of radiation that causes cancer?

Dr. CARACAPPA: Yes.

MONTAGNE: So what then is the largest contributor of ionizing radiation?

Dr. CARACAPPA: For the natural sources of ionizing radiation, actually the biggest chunk of that tends to come from radon, which is a radioactive material that is present in the air. It can become a concern because of the construction of certain homes or where they're located or the ground surrounding them that would allow that gas to build up to higher levels in, you know, kind of low-lying areas of homes, like basements.

MONTAGNE: So is that worth being vigilant about in terms of trying to protect ourselves from radon?

Dr. CARACAPPA: The general principle of radiation protection is that radiation should be kept as low as reasonably achievable. So the idea behind this is that any small amount of radiation carries with it some comparably small amount of risk. So for radon in basements there's, you know, there's some easy fixes that allow you to reduce the radon exposure. If it's easy to do, then less is better.

MONTAGNE: Would it be fair to say that most people do not need to worry about the danger of being exposed to radiation?

Dr. CARACAPPA: I would say that the everyday exposure to radiation that we encounter contributes an extremely tiny risk to our life or to our health, compared to all of the other risks that we encounter in our day-to-day life.

MONTAGNE: Thank you very much for joining us.

Dr. CARACAPPA: Oh, thank you.

MONTAGNE: Peter Caracappa is a professor of nuclear engineering at Rensselaer Polytechnic Institute in Troy, New York.

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