How did radiation exposure affect survivors of the atomic bombings?

The survivors of the atomic bombings of Hiroshima and Nagasaki, known as hibakusha, experienced severe health consequences due to radiation exposure. These effects were categorized into immediate injuries and long-term health risks.1

Immediate Effects

Radiation injuries caused by gamma rays and neutrons at the instant of the explosions accounted for approximately 10 percent of deaths in Hiroshima and 6 percent in Nagasaki. Intensive irradiation led to acute radiation syndrome, characterized by early symptoms such as loss of appetite, nausea, and vomiting. Later phases of this illness included fever, weakness, hair loss, infection, and hemorrhage, often resulting in death from infection or uncontrollable bleeding.12

Long-term Health Consequences

• Cancer: Survivors exhibited dose-dependent increases in the incidence of various cancers, most notably leukemia and breast cancer. Other solid cancers, including those of the thyroid, stomach, colon, liver, lung, bladder, and ovary, have also been linked to radiation exposure.23
• Developmental Abnormalities: Children exposed to radiation in utero, particularly between the 8th and 15th weeks of gestation, showed a higher-than-normal frequency of intellectual disability and reduced head size.2
• Genetic Effects: Despite exhaustive studies, researchers have not yet observed heritable genetic effects in the children of survivors, likely due to the relatively small average radiation doses received by the parents.4