text: Some estimates are that 140,000 people in Hiroshima (38.9% of the population) and 70,000 people in Nagasaki (28.0% of the population) died in 1945, but how many died immediately as a result of exposure to the blast, heat, or due to radiation, is unknown. One Atomic Bomb Casualty Commission (ABCC) report discusses 6,882 people examined in Hiroshima, and 6,621 people examined in Nagasaki, who were largely within 2000 meters from the hypocenter, who suffered injuries from the blast and heat but died from complications frequently compounded by acute radiation syndrome (ARS), all within about 20–30 days.
  In the rare cases of survival for individuals who were in utero at the time of the bombing and yet who still were close enough to be exposed to less than or equal to 0.57 Gy, no difference in their cognitive abilities was found, suggesting a threshold dose for pregnancies below which there is no danger. In 50 or so children who survived the gestational process and were exposed to more than this dose, putting them within about 1000 meters from the hypocenter, microcephaly was observed; this is the only elevated birth defect issue observed in the Hibakusha, occurring in approximately 50 in-utero individuals who were situated less than 1000 meters from the bombings.