BY H. JOSEF HEBERT
WASHINGTON -- Even low doses of radiation pose a risk of cancer over a person's lifetime, a National Academy of Sciences panel concluded. It rejected some scientists' arguments that tiny doses are harmless or might in fact be beneficial.
The findings, disclosed in a report Wednesday, could influence the maximum radiation levels that are allowed at abandoned reactors and other nuclear sites and could raise warnings about excessive exposure to radiation for medical purposes such as repeated whole-body CT scans.
"It is unlikely that there is a threshold (of radiation exposure) below which cancers are not induced," the scientists said.
While at low doses "the number of radiation-induced cancers will be small ... as the overall lifetime exposure increases, so does the risk," they said.
There is evidence that per unit of absorbed radiation, X-rays might be more dangerous than other radiation, the scientists found, and one person out of 1,000 would develop cancer from exposure to the amount of radiation from a single, average whole body CT scan.
But the report should not scare people away from nuclear medicine, said Dr. Henry Royal, a professor of radiology at Washington University in St. Louis. He said most often the benefits of such tests and treatments outweigh the risks.
But he also said procedures such as CT scans should be used for specific medical problems and not as part of annual medical screenings. "You should not be exposed to radiation for superficial reasons," Royal said in a telephone interview.
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