The initial radiation sickness, due to intense gamma radiation from the blast itself, was devastating, causing many deaths for about 6-8 weeks. Since it was an air burst there was relatively little fallout lingering around to cause cancer in the long term.
Yes,
There are two radiation effects.
Initial radiation sickness, caused by short mega doses of radiation, which is quite deadly.
Then there are long term effects, lingering from exposure to medium doses of radiation. These effects are quite overestimated, as the bodies have ability to recover, which is not taken in account by overly conservative assessments.
Good arguments are made that we actually need some low level radiation exposure. Places with high level of natural radiation are usually healthy spas, with low number of cancers, a lot better than places with very low natural radiation levels.
But the population is hysterical about radiation exposure, fed by media and the “invisible dead rays” scare.