The cancer mortality risk for 70-year-olds who absorbed 1 sievert of radiation in the atomic bombings of Hiroshima and Nagasaki when they were 30 is 42 percent higher than those who weren't exposed to the attacks, a Hiroshima institute survey says.
The Radiation Effects Research Foundation, a Japan-U.S. research body, unveiled the cancer mortality findings — which exclude leukemia — in Thursday's issue of the U.S. journal Radiation Research.
The foundation studied the medical records of around 87,000 hibakusha between 1950 and 2003. About 51,000 had already died, 11,000 of them from cancer.
The study also said that the cancer mortality risk for those who were 20 at the time they were exposed was 54 percent higher than for those who did not experience the nuclear attacks.
Kotaro Ozasa, head of the foundation's department of epidemiology, said the institute must further research the correlation between radiation and noncancerous ills and also on the effects of low-level and residual radiation.