New research challenges the belief that exposure to nuclear radiation has a negligible genetic effect on human beings, indicating that it can lead to an increase in male births.
Hagen Scherb and Kristina Voigt from the Helmholtz Zentrum München say they've discovered that that radiation from atomic bomb testing before the Partial Test Ban Treaty in 1963, the Chernobyl accident and from living near nuclear facilities has had a long-term negative effect on the ratio of male to female human births.
Their research unearthed an increase in male births relative to female births in Europe and the US between 1964 and 1975 - "A likely consequence of the globally emitted and dispersed atmospheric atomic bomb test fallout, prior to the test ban in 1963, that affected large human populations overall after a certain delay," they say.
They also found a significant jump of sex odds in Europe in 1987 - the year after the Chernobyl disaster - whereas no similar effect was seen in the US, which was less exposed to radiation.
And the sex odds also increased significantly among populations living within 22 miles of functioning nuclear facilities in Germany and Switzerland.
The researchers say they can't tell whether they're observing a reduced frequency of female births or an increased number of male births. But they say that the deficit of births and the number of stillborn or impaired children after the global releases of ionizing radiation amount to several millions globally.
"Our results contribute to disproving the established and prevailing belief that radiation-induced hereditary effects have yet to be detected in human populations," they say.
"We find strong evidence of an enhanced impairment of humankind's genetic pool by artificial ionizing radiation."