"We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another."
-J. Robert Oppenheimer, in an interview recalling the 1945 Trinity Test. |
The Bombing of Hiroshima
A single atomic bomb, the first weapon of its type ever used against a target, exploded over the city of Hiroshima at 8:15 on the morning of 6 August 1945. Most of the industrial workers had already reported to work, but many workers were enroute and nearly all the school children and some industrial employees were at work in the open on the program of building removal to provide firebreaks and disperse valuables to the country. The attack came 45 minutes after the "all clear" had been sounded from a previous alert. Because of the lack of warning and the populace's indifference to small groups of planes, the explosion came as an almost complete surprise, and the people had not taken shelter. Many were caught in the open, and most of the rest in flimsily constructed homes or commercial establishments.
The bomb exploded slightly northwest of the center of the city. Because of this accuracy and the flat terrain and circular shape of the city, Hiroshima was uniformly and extensively devastated. Practically the entire densely or moderately built-up portion of the city was leveled by blast and swept by fire. A "fire-storm," a phenomenon which has occurred infrequently in other conflagrations, developed in Hiroshima: fires springing up almost simultaneously over the wide flat area around the center of the city drew in air from all directions. The inrush of air easily overcame the natural ground wind, which had a velocity of only about 5 miles per hour. The "fire-wind" attained a maximum velocity of 30 to 40 miles per hour 2 to 3 hours after the explosion. The "fire-wind" and the symmetry of the built-up center of the city gave a roughly circular shape to the 4.4 square miles which were almost completely burned out.
The surprise, the collapse of many buildings, and the conflagration contributed to an unprecedented casualty rate. Seventy to eighty thousand people were killed, or missing and presumed dead, and an equal number were injured. The magnitude of casualties is set in relief by a comparison with the Tokyo fire raid of 9-10 March 1945, in which, though nearly 16 square miles were destroyed, the number killed was no larger, and fewer people were injured.
The bomb exploded slightly northwest of the center of the city. Because of this accuracy and the flat terrain and circular shape of the city, Hiroshima was uniformly and extensively devastated. Practically the entire densely or moderately built-up portion of the city was leveled by blast and swept by fire. A "fire-storm," a phenomenon which has occurred infrequently in other conflagrations, developed in Hiroshima: fires springing up almost simultaneously over the wide flat area around the center of the city drew in air from all directions. The inrush of air easily overcame the natural ground wind, which had a velocity of only about 5 miles per hour. The "fire-wind" attained a maximum velocity of 30 to 40 miles per hour 2 to 3 hours after the explosion. The "fire-wind" and the symmetry of the built-up center of the city gave a roughly circular shape to the 4.4 square miles which were almost completely burned out.
The surprise, the collapse of many buildings, and the conflagration contributed to an unprecedented casualty rate. Seventy to eighty thousand people were killed, or missing and presumed dead, and an equal number were injured. The magnitude of casualties is set in relief by a comparison with the Tokyo fire raid of 9-10 March 1945, in which, though nearly 16 square miles were destroyed, the number killed was no larger, and fewer people were injured.
Aftermath
The impact of the atomic bomb shattered the normal fabric of community life and disrupted the organizations for handling the disaster. In the 30 percent of the population killed and the additional 30 percent seriously injured were included corresponding proportions of the civic authorities and rescue groups. A mass flight from the city took place, as persons sought safety from the conflagration and a place for shelter and food. Within 24 hours, however, people were streaming back by the thousands in search of relatives and friends and to determine the extent of their property loss. Road blocks had to be set up along all routes leading into the city, to keep curious and unauthorized people out. The bulk of the dehoused population found refuge in the surrounding countryside; within the city the food supply was short and shelter virtually nonexistent.
The status of medical facilities and personnel dramatically illustrates the difficulties facing authorities. Of more than 200 doctors in Hiroshima before the attack, over 90 percent were casualties and only about 30 physicians were able to perform their normal duties a month after the raid. Out of 1,780 nurses, 1,654 were killed or injured. Through some stocks of supplies had been dispersed, many were destroyed.
Only three out of 45 civilian hospitals could be used, and two large Army hospitals were rendered unusable. Those within 3,000 feet of ground zero were totally destroyed, and the mortality rate of the occupants was practically 100 percent. Two large hospitals of reinforced concrete construction were located 4,900 feet from ground zero. The basic structures remained erect but there was such severe interior damage that neither was able to resume operation as a hospital for some time and the casualty rate was approximately 90 percent, due primarily to falling plaster, flying glass, and fire. Hospitals and clinics beyond 7,000 feet, though often remaining standing, were badly damaged and contained many casualties from flying glass or other missiles.
The water reservoir, which was of reinforced concrete and earth-covered, was undamaged; it was nearly 2 miles from the blast center. However, 70,000 breaks of pipe connections in buildings and dwellings were caused by blast and fire effects. No subsurface pipes were crushed and no leaks resulted from blast as a direct cause, though several leaks in underground mains resulted from falling debris. Pressure in the city center dropped to zero because of the connection breaks and the damage to a 16- and a 14-inch water main where they crossed damaged bridges. Six sewer pumping stations were rendered inoperable by fire and blast within a radius of 1 mile. The remaining eight stations were only slightly damaged, but no effort was made to repair or operate them. Water tables rose at flood periods and lands behind revetments were inundated.
The electric power transmission and distribution system was wrecked; only power equipment of rugged construction, such as transformers, resisted the blast and heat within the devastated areas. Instruments were damaged beyond repair, and switches, switchyard insulators, cables, and copper bus work were rendered unusable. The telephone system was approximately 80 percent damaged, and no service was restored until 15 August 1945.
The U.S. Strategic Bombing Survey believes the dead at Hiroshima to have been between 70,000 and 80,000, with an equal number injured as the most plausible casualty estimate.
Most of the immediate casualties did not differ from those caused by incendiary or high-explosive raids. The outstanding difference was the presence of radiation effects, which became unmistakable about a week after the bombing. At the time of impact, however, the causes of death and injury were flash burns, secondary effects of blast and falling debris, and burns from blazing buildings. No records are available that give the relative importance of the various types of injury, especially for those who died immediately after the explosion. Indeed, many of these people undoubtedly died several times over, theoretically, since each was subjected to several injuries, any one of which would have been fatal. The Hiroshima prefectural health department placed the proportion of deaths from burns (flash or flame) at 60 percent, from falling debris at 30 percent, and from other injuries at 10 percent; it is generally agreed that burns caused at least 50 percent of the initial casualties. Of those who died later, an increasing proportion succumbed to radiation effects.
Source: https://www.ibiblio.org/hyperwar/AAF/USSBS/AtomicEffects/AtomicEffects-2.html
The status of medical facilities and personnel dramatically illustrates the difficulties facing authorities. Of more than 200 doctors in Hiroshima before the attack, over 90 percent were casualties and only about 30 physicians were able to perform their normal duties a month after the raid. Out of 1,780 nurses, 1,654 were killed or injured. Through some stocks of supplies had been dispersed, many were destroyed.
Only three out of 45 civilian hospitals could be used, and two large Army hospitals were rendered unusable. Those within 3,000 feet of ground zero were totally destroyed, and the mortality rate of the occupants was practically 100 percent. Two large hospitals of reinforced concrete construction were located 4,900 feet from ground zero. The basic structures remained erect but there was such severe interior damage that neither was able to resume operation as a hospital for some time and the casualty rate was approximately 90 percent, due primarily to falling plaster, flying glass, and fire. Hospitals and clinics beyond 7,000 feet, though often remaining standing, were badly damaged and contained many casualties from flying glass or other missiles.
The water reservoir, which was of reinforced concrete and earth-covered, was undamaged; it was nearly 2 miles from the blast center. However, 70,000 breaks of pipe connections in buildings and dwellings were caused by blast and fire effects. No subsurface pipes were crushed and no leaks resulted from blast as a direct cause, though several leaks in underground mains resulted from falling debris. Pressure in the city center dropped to zero because of the connection breaks and the damage to a 16- and a 14-inch water main where they crossed damaged bridges. Six sewer pumping stations were rendered inoperable by fire and blast within a radius of 1 mile. The remaining eight stations were only slightly damaged, but no effort was made to repair or operate them. Water tables rose at flood periods and lands behind revetments were inundated.
The electric power transmission and distribution system was wrecked; only power equipment of rugged construction, such as transformers, resisted the blast and heat within the devastated areas. Instruments were damaged beyond repair, and switches, switchyard insulators, cables, and copper bus work were rendered unusable. The telephone system was approximately 80 percent damaged, and no service was restored until 15 August 1945.
The U.S. Strategic Bombing Survey believes the dead at Hiroshima to have been between 70,000 and 80,000, with an equal number injured as the most plausible casualty estimate.
Most of the immediate casualties did not differ from those caused by incendiary or high-explosive raids. The outstanding difference was the presence of radiation effects, which became unmistakable about a week after the bombing. At the time of impact, however, the causes of death and injury were flash burns, secondary effects of blast and falling debris, and burns from blazing buildings. No records are available that give the relative importance of the various types of injury, especially for those who died immediately after the explosion. Indeed, many of these people undoubtedly died several times over, theoretically, since each was subjected to several injuries, any one of which would have been fatal. The Hiroshima prefectural health department placed the proportion of deaths from burns (flash or flame) at 60 percent, from falling debris at 30 percent, and from other injuries at 10 percent; it is generally agreed that burns caused at least 50 percent of the initial casualties. Of those who died later, an increasing proportion succumbed to radiation effects.
Source: https://www.ibiblio.org/hyperwar/AAF/USSBS/AtomicEffects/AtomicEffects-2.html
Effects of Radiation
At the time of the atomic bombing of Japan, the study of the effects of radiation was in its infancy. Little data was available that would have enabled war planners to realize the possible effects of radiation from the atomic bomb on population centers. However, the reality of the effects of radiation would soon be realized from studies conducted after the bombings of Hiroshima and Nagasaki.
Among the long-term effects suffered by atomic bomb survivors, the most deadly was leukemia. An increase in leukemia appeared about two years after the attacks and peaked around four to six years later. Children represent the population that was affected most severely. Attributable risk—the percent difference in the incidence rate of a condition between an exposed population and a comparable unexposed one — reveals how great of an effect radiation had on leukemia incidence. The Radiation Effects Research Foundation estimates the attributable risk of leukemia to be 46% for bomb victims.
For all other cancers, incidence increase did not appear until around ten years after the attacks. The increase was first noted in 1956 and soon after tumor registries were started in both Hiroshima and Nagasaki to collect data on the excess cancer risks caused by the radiation exposure. The most thorough study regarding the incidence of solid cancer (meaning cancer that is not leukemia) was conducted by a team led by Dale L. Preston of Hirosoft International Corporation and published in 2003. The study estimated the attributable rate of radiation exposure to solid cancer to be significantly lower than that for leukemia—10.7%. According to the RERF, the data corroborates the general rule that even if someone is exposed to a barely survivable whole-body radiation dose, the solid cancer risk will not be more than five times greater than the risk of an unexposed individual.
Among the long-term effects suffered by atomic bomb survivors, the most deadly was leukemia. An increase in leukemia appeared about two years after the attacks and peaked around four to six years later. Children represent the population that was affected most severely. Attributable risk—the percent difference in the incidence rate of a condition between an exposed population and a comparable unexposed one — reveals how great of an effect radiation had on leukemia incidence. The Radiation Effects Research Foundation estimates the attributable risk of leukemia to be 46% for bomb victims.
For all other cancers, incidence increase did not appear until around ten years after the attacks. The increase was first noted in 1956 and soon after tumor registries were started in both Hiroshima and Nagasaki to collect data on the excess cancer risks caused by the radiation exposure. The most thorough study regarding the incidence of solid cancer (meaning cancer that is not leukemia) was conducted by a team led by Dale L. Preston of Hirosoft International Corporation and published in 2003. The study estimated the attributable rate of radiation exposure to solid cancer to be significantly lower than that for leukemia—10.7%. According to the RERF, the data corroborates the general rule that even if someone is exposed to a barely survivable whole-body radiation dose, the solid cancer risk will not be more than five times greater than the risk of an unexposed individual.