They studied the population in Hiroshima and Nagasaki for generations and found that in the first generations after the bombs there were elevated levels of hard-tissue cancers and in later generations elevated levels of soft-tissue/blood cancers. They're still dealing with the population effects of radiation 75-years later.
No one will be able to live in Chernobyl or Fukushima for hundreds of years. Or, well, they could but it would be stupid.