With everyone else, I want to see some source on this. We had a ton of people die of radiation poisoning during the construction of the bomb, and even before that. There was plenty of research done ahead of time, and we knew what would happen.
I would like to point out that the American government wasn't exactly sure what would have happened, they did tests in the 50s and 60s to find out, there's a famous clip of 'five men at ground zero', five men volunteered to stand under the mushroom cloud to see what would happen to them.
I think it would also be a good point to say that they all lived over sixty and two of the blokes (including the cameraman) are still alive today.
http://www.youtube.c...bed/BlE1BdOAfVc
The thing is, a lot of detonations were conducted in Texas in the 50s and because the scientists conducting the test didn't fully grasp the consequence of radiation poisoning, they used to let locals go and stand /right under/ the mushroom clouds. They also tested very near to villages. I tried to find a primary source on it but after about 15 minutes of searching I realised I can't for the life of me remember the exact title. Basically a guy and his wife went to watch the detonation of an A-Bomb and his wife's skin went red and peeled away, she became very ill and died five years later of advanced cancer or something.
That's why you have that sudden surge of public announcements videos in the late 50s and throughout the 60s and 70s, I think the government suddenly realised that the world had created weapons that were more dangerous then they ever realised in 1945.