This study does show that there is an effect on genetic mutation

Maj Hulten, University of Warwick:

Their children had a five-fold increased risk.

And the study showed there was a increased risk for children born to older parents, who had had higher exposure to the radioactive fallout.

Although the genetic mutations seen by the researchers did not have any physical manifestations, the team say the study does show the ability of high-strength radioactivity to affect DNA.

The scientists, writing in the journal Science, said the Moscow treaty in 1963 banning nuclear weapons tests in the atmosphere had been "effective in reducing genetic risk to the affected population".

Test history

Maj Hulten, professor of medical genetics at the University of Warwick, who worked on the research, said: "This study does show that there is an effect on genetic mutation.

"It also would mean that in some other forms [radiation] could hit genes which have relevance for development."

She added that the genetic material which has been collected from the families provides a "biobank" which further research can be carried out on in the future.

William Morgan, director of the Radiation Oncology Research Laboratory at the University of Maryland School of Medicine in Baltimore told Science the findings could contribute to the current debate about how people can be protected from chronic low-dose radiation.