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Radiation risks

From the "Wolf Blitzer Reports" staff
CNN

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A patient gets a full-body image X-ray.

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WASHINGTON (CNN) -- We get them at the dentist's and doctor's offices and more recently, at full-body imaging centers that have opened across the country.

Few people give X-rays much thought, but a new report from the National Academy of Sciences finds that even at the very lowest levels, X-rays and other types of ionizing radiation have the potential to cause cancer.

The study emphasizes the risk is very small, but concludes, "There is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless or beneficial."

But what is considered a low level?

Ionizing radiation is measured in millisieverts which represent energy deposited in living tissue.

The study defines a low dose as zero to 100 millisieverts.

To put it in perspective, the study says each of us is exposed to about three millisieverts of so-called background radiation from the universe each year.

One chest X-ray adds a scant one-tenth of a millisievert to that.

Even 100 chest X-rays -- one person out of 100 would be expected to develop cancer as a result of radiation exposure. By comparison, the study continues, about 42 out of 100 would be expected to develop cancer from other causes.

But exposure is measured over a lifetime -- and as it increases so does the risk.

The findings support earlier studies -- and scientists say more research is needed -- especially on the effects of CAT scans which typically result in higher doses of radiation.

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