Perhaps most reassuring of this is the view of the cityscapes themselves. Among some there is the unfounded fear that Hiroshima and Nagasaki are still radioactive; in reality, this is not true. Following a nuclear explosion, there are two forms of residual radioactivity. The first is the fallout of the nuclear material and fission products. Most of this was dispersed in the atmosphere or blown away by the wind. Though some did fall onto the city as black rain, the level of radioactivity today is so low it can be barely distinguished from the trace amounts presents throughout the world as a result of atmospheric tests in the 1950s and 1960s. The other form of radiation is neutron activation. Neutrons can cause non-radioactive materials to become radioactive when caught by atomic nuclei. However, since the bombs were detonated so far above the ground, there was very little contamination—especially in contrast to nuclear test sites such as those in Nevada. In fact, nearly all the induced radioactivity decayed within a few days of the explosions.

Today, the liveliness of the cities of Hiroshima and Nagasaki serves as a reminder not only of the human ability to regenerate, but also of the extent to which fear and misinformation can lead to incorrect expectations. After the bombings of Hiroshima and Nagasaki, many thought that any city targeted by an atomic weapon would become a nuclear wasteland. While the immediate aftermath of the atomic bombings was horrendous and nightmarish, with innumerable casualties, the populations of Hiroshima and Nagasaki did not allow their cities to become the sort of wasteland that some thought was inevitable. This experience of can serve as lesson in the present when much of the public and even some governments have reacted radically to the accident in Fukushima--in the midst of tragedy, there remains hope for the future.

Further Reading:

The Radiation Effects Research Foundation site outlines the results of numerous studies regarding the survivors of Hiroshima and Nagasaki.

The Hiroshima Peace Memorial Museum site discusses the recovery efforts of the city of Hiroshima after the atomic bombing.

A study by Hirosoft International analyzes the incidence of solid cancer in atomic bomb survivors.

In The Children of Atomic Bomb Survivors: A Genetic Study, the authors overview a number of studies on children of parents exposed to atomic bombs.

Bibliography:

D. L. Preston, E. Ron, S. Tokuoka, S. Funamoto, N. Nishi, M. Soda, K. Mabuchi, and K. Kodama. (2007) Solid cancer incidence in atomic bomb survivors: 1958-1998. Radiation Research 168:1, 1-64

E. J. Grant, K Ozasa, D. L. Preston, A Suyama, Y Shimizu, R Sakata, H Sugiyama, T-M Pham, J Cologne, M Yamada, A. J. De Roos, K. J. Kopecky, M. P. Porter, N Seixas and S Davis. (2012) Effects of Radiation and Lifestyle Factors on Risks of Urothelial Carcinoma in the Life Span Study of Atomic Bomb Survivors. Radiation Research 178:1, 86-98

"Radiation Health Effects." - Radiation Effects Research Foundation. Radiation Effects Research Foundation, 2007. Web. 29 July 2012.

W. F. Heidenreich, H. M. Cullings, S. Funamoto and H. G. Paretzke. (2007) Promoting Action of Radiation in the Atomic Bomb Survivor Carcinogenesis Data?. Radiation Research 168:6, 750-756