Atomic bombings of Hiroshima and Nagasaki
Post-attack casualties

An estimated 90,000 to 166,000 people in Hiroshima (between 26 and 49 percent of its population) and 60,000 to 80,000 people in Nagasaki (between 22 and 32 percent of its population) died in 1945, of which a majority in each case were killed on the days of the bombings, due to the force and heat of the blasts themselves. Nearly all of the remainder of victims died within two to four months, due to radiation exposure and resulting complications.

One Atomic Bomb Casualty Commission report discusses 6,882 people examined in Hiroshima and 6,621 people examined in Nagasaki, who were largely within 2,000 meters (6,600 ft) of the hypocenter, who suffered injuries from the blast and heat but died from complications frequently compounded by acute radiation syndrome (ARS), all within about 20 to 30 days. Many people not injured by the blast eventually died within that timeframe as well after suffering from ARS. At the time, the doctors had no idea what the cause was and were unable to effectively treat the condition. Midori Naka was the first death officially certified to be the result of radiation poisoning or, as it was referred to by many, the "atomic bomb disease". She was some 650 meters (2,130 ft) from the hypocenter at Hiroshima and would die on 24 August 1945 after traveling to Tokyo. It was unappreciated at the time but the average radiation dose that would kill approximately 50 percent of adults (the LD50) was approximately halved; that is, smaller doses were made more lethal when the individual experienced concurrent blast or burn polytraumatic injuries. Conventional skin injuries that cover a large area frequently result in bacterial infection; the risk of sepsis and death is increased when a usually non-lethal radiation dose moderately suppresses the white blood cell count.

In the spring of 1948, the Atomic Bomb Casualty Commission (ABCC) was established in accordance with a presidential directive from Truman to the National Academy of Sciences – National Research Council to conduct investigations of the late effects of radiation among the survivors in Hiroshima and Nagasaki. In 1956, the ABCC published The Effect of Exposure to the Atomic Bombs on Pregnancy Termination in Hiroshima and Nagasaki. The ABCC became the Radiation Effects Research Foundation (RERF) on 1 April 1975. A binational organization run by both the United States and Japan, the RERF is still in operation today.
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