Damage by Radiation - another quote from Hiroshima Peace Memorial Museum

Damage by the Radiation

Acute Effects

Symptoms of radiation poisoning that appeared immediately after the atomic bombing are called acute effects. The unique characteristic of the atomic bombs was the massive amount of radiation they emitted. Conventional bombs emit no such radiation. This radiation severely damaged victims' bodies. Radiation destroys cells, alters blood quality, damages blood marrow and other blood-forming organs, and causes other serious injury. Anyone directly exposed to radiation within 1,000 meters from thehypocenter received a life-threatening dose, and most died within a few days. Some who appeared completely uninjured began vomiting blood or died with purple spots all over their bodies.