How do you feel that the dropping of an atomic bomb has affected the world?

Hiroshima

An American B-29 bomber called the Enola Gay took off from the tiny island of Tinian in the Northern Marianas group in the west Pacific Island and dropped an atomic bomb on the city of Hiroshima on 6 August 1945 at 08:12 local time. 90,000-140,000 people died immediately or within the first 4 months. The bomb on Nagasaki three days later killed a further 40,000. About 100,000 who survived the bombs died slow painful deaths later from severe burns and/or radiation. Others survived but with injuries such as burns. Japan surrendered on 15 August. The rationale for the bombing is that it brought the war to an end sooner, without the necessity for an invasion of Japan, thus saving many lives. Some dispute this, saying that Japan would have surrendered before the invasion, scheduled for the December, in any case. Various figures have been suggested for how many lives would have been saved. I don't intend to debate those arguments here, only to look one side of the equation - what was the cost to the environment, particularly the people?

The Hiroshima bomb was called "Little Boy". The uranium that was used to make the bomb came from the Shinkolobwe mine in what is now the Democratic Republic of Congo. About 60 kilograms of highly enriched uranium 235 was used. The bomb exploded at a height of about 576 metres above the city with a force of about 13 kilotons. The first shock wave travelled at about 335 metres per second. The explosion generated a wave of about 4,000C (7,200F) with a radius of about 4.5km (2.8 miles). It destroyed the city. Because the bomb exploded quite high up in the air, material from the ground did not get taken up only to return to the ground as radioactive fallout. There was some local rain to the west and north-west of the city that became radioactive, however, but as only about 10% of the nuclear material in the bombs underwent fission, there was not a great deal of this. The remaining fission products were dispersed high in the air. The longest half-life of the products that were formed was the two years of caesium-134, so Hiroshima is not radioactive now as a result of the blast.

Scientists have tried to estimate how much radiation that people were exposed to by the bomb. High-energy or fast neutrons are thought to cause one in five cancers, but it was not possible to test how many the bomb released. However, when particles from the bomb hit copper, they produce a nickel isotope, and it has been possible to analyse metal lightning rods and gutters from Hiroshima for it. Individual doses varied not only on distance from the bomb, but also on whether they were sheltered by a structure such as a wall.

The Japanese call the survivors Hibakusha; you may have seen some on television remembering their experiences on this 60th anniversary. Many who were apparently untouched know that they were exposed to radiation, and they have been living with the fear that any symptom might be the first sign of cancer ever since. Their average age is 72 now, and it is expected that cancer rates will continue to rise among them. They have been intensely studied by the Radiation Effects Research Foundation, and the guidelines for safe exposure to radiation that are used world-wide are based on their experience. The foundation is also studying the children of the Hibakusha, but so far no genetic effects have been found. They are also studying those who were in utero at the time. There were many birth deformities and stillbirths over the 9 months after the bomb was dropped. There do not appear to have been any studies of animals or plants. This is perhaps not surprising, as in the early years when the effects were most measurable people will have been concentrating on recovery.

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