The Chernobyl disaster reportedly resulted in 237 people suffering from acute radiation sickness of which 31 died. These were mostly people who formed part of fire and rescue teams and therefore experienced close direct exposure to lethal doses of radiation. Because of this disaster being so recent there is still no reliable statistics on the incidence of cancer related to the general population affected by the fallout coming from this accident.
However, the survivors of the atomic bombing of Hiroshima and Nagasaki 66 years ago have been extensively studied. The study revealed that out of an estimated 100,000 survivors of those atomic explosions [known as hibakusha among the Japanese], an estimated 500 died prematurely from cancer directly related to radiation exposure. This translates to a 0.5 percent probability of developing cancer as a result of exposure to radiation. However, in absolute numbers, that statistic is still significant. It puts 4,000 people out of the 800,000 estimated to have been exposed to radiation coming from the Chernobyl disaster as being likely to die from cancer in the coming years.
To put these figures in perspective, consider that 8,000 Americans are killed by skin cancer caused by excessive exposure to the sun's radiation every year. Particulates and other derivative pollutants coming from fossil fuel combustion could also be signficant contributors to hundreds of thousands of deaths every year.
These figures related to the risks of radiation exposure deaths in the event of a catastrophe in Japan though moderately comforting do not take into account effects of radiation on women who happen to be pregnant at the time of exposure...
We also know that many of the children of hibakusha women pregnant at the time they were exposed suffered horrible birth defects. Studies of the atomic bomb survivors have also taught us, however, that there is apparently no generational genetic impact from radiation exposure. Kids born to parents who got pregnant after the exposure, were normal.
Indeed, in the bigger scheme of planetary life, the fact that wildlife is now observed to be thriving in the immediate areas around Chernobyl (which were made off limits to humans since the accident) is a testament to the reality that direct human presence represents a far bigger hazard to nature than nuclear reactor meltdowns.