Fwd: [Getting Well] Study: Damage stays from low-dose X-rays

April 2, 2003

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Study: Damage stays from low-dose X-rays

WASHINGTON (Reuters) -- Low doses of X-rays such as those patients

receive in the dentist's chair may do more long-lasting damage than

higher doses, German scientists reported on Monday in a study that

turns common wisdom on its head.

Their findings, based on experiment with cell cultures, will have to

be duplicated by other labs and then repeated in living animals

before doctors can offer guidance on the effects of low-dose X-rays

on humans.

The team, led by Markus Lobrich at the Universitat des Saarlandes,

said its reasearch suggests that doses of X-rays generally

considered harmless may in fact do long-lasting damage.

But they said they had developed a test that would help doctors look

for genetic damage in people exposed to low doses of X-rays, such as

cancer patients undergoing radiotherapy, patients getting X-rays and

professionals working with X-ray equipment.

Writing in the Proceedings of the National Academy of Sciences,

Lobrich's team said they exposed human cell cultures to varying X-

ray doses in the laboratory.

To their surprise, they found that damage from low radiation levels

lingered days to weeks longer than damage caused by more powerful

levels.

Ionizing radiation like the kind produced by X-rays and some nuclear

breakdown products can cause leukemia and other cancers. The

radiation can cause breaks in DNA that go across both strands of its

double helix structure.

Scientists had assumed that the body moves to repair these breaks at

the same rate, no matter what the dose of radiation.

But Lobrich's team found this may not be true. It could be, they

propose, that the body simply does not recognize lower levels of

damage and does not move to repair it.

When these damaged cells divide and multiply, the unrepaired damage

multiplies along with them, they suggested

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