Study: Radiation Caused Mutations

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FEBRUARY 07, 14:01 ET

Study: Radiation Caused Mutations

By PAUL RECER

AP Science Writer

WASHINGTON (AP) - Radiation from Soviet atomic bomb testing caused gene

mutations in families living nearby, according to a new study, but

researchers say it is not known if the genetic changes caused adverse health

effects.

The study, appearing Friday in the journal Science, gives new evidence that

low-dose radiation from atomic bomb fallout can cause genetic mutation that

can be passed to a new generation, but the study did not find any health

consequences from these DNA changes, experts say.

A group of European researchers led by Yuri E. Dubrova of the University of

Leicester took blood samples from 40 families in an area of Kazakstan not

far from the Semipalatinsk site where the former Soviet Union conducted

atomic bomb tests.

For a control group, the researchers took blood samples from 28 families in

a geographically similar region of Kazakstan that had not been exposed to

radiation from the tests.

Members of the study group and the control group were matched by year of

birth, occupation and ethnicity.

The researchers then checked DNA of the two groups for evidence of mutations

that could have been passed from one generation to another.

For the generation exposed to radiation from bomb tests in 1949, 1951, 1953

and 1956, the study found a mutation rate that was about 80 percent higher

than in the corresponding generation in the control group.

In the children of the exposed generation, the researchers found a mutation

rate about 50 percent greater than in the group that had not been exposed to

radiation.

All the mutations were found in what is known as ``junk DNA,'' bits of

genetic material that have no known function.

``These are mutations, but not in critical genes and there is not anything

that we can correlate with a health effect,'' said Dr. F. ,

director of the Radiation Oncology Research Laboratory at the University of

land, Baltimore.

, who reviewed the study for Science, said the findings give new

understanding of how ionizing radiation, such as from an atomic bomb and its

fallout, can affect successive generations.

Most of what is known about such radiation effects comes from survivors of

the atomic bombs dropped on Japan during World War II. Those survivors were

exposed to a single, severe dose of radiation. No inherited mutations were

found in that group, said , but it was rare that both parents in the

Japanese bombings were equally exposed.

In the new study, he said, ``they are finding that if you live in an

environment that is contaminated where you are continuously exposed, then

you start to see these increases'' in mutations.

Dubrova and his colleagues found that the rate of mutations declined with

the passage of time once the bomb tests stopped. They said this suggests

that the 1963 treaty banning aboveground nuclear weapons testing ``has been

effective in reducing genetic risk to the affected population.''

said the findings are consistent with animal studies that showed

low-level, chronic exposure to radiation, such as from the fallout of bomb

tests, can cause some genetic mutations that are passed to the next

generation.

Such mutations, he said, can be traced to radiation exposure affecting sperm

at a critical phase of its development.

The mutations that pass to the next generation originate ``predominantly on

the male side'' of reproduction, said.

In an earlier study, Dubrova found similar mutations among families exposed

to fallout from the 1986 nuclear power plant accident at Chernobyl in the

Ukraine. The deaths of about 8,000 people in the Ukraine, Russia and Belarus

have been blamed on the incident, but another 200,000 are thought to live in

areas still contaminated.

Dubrova's Chernobyl study, published in Nature in 1996, found that children

of men living in the contaminated area of Belarus had about twice as many

mutations as a comparison group in Britain. Many researchers said that study

was flawed.

But said the new study in Kazakstan supports Dubrova's earlier

findings.

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On the Net:

Science: http://www.sciencemag.org