There has been a slight increase in the number of girls studying physics in recent years but this has been dwarfed by a more rapid increase in boys studying the subject.
It said that schools should be set targets by the government to increase the proportion of girls studying physics from the current national average of just one in five.
"On the basis of the radiation doses people have received, there is no reason to think there would be an increase in cancer in the next 50 years, " said Wade Allison, an emeritus professor of physics at Oxford University, who was not connected to the WHO report.