Ahh ha! You have failed to understand that all radiation is not equal, and also mechanisms of exposure are not equal.
If someone made a bet with me that I should swallow a pellet of plutonium in a plastic case or something bad would happen to a loved one, I would swallow the plutonium and trust to my digestion and the container. If I had to breath in the plutonium in a dust instead I would still do it (for love) but I think it would be the death of me.
So - looking at the radiation released in total : has there been a massive increase in deaths due to atmospheric testing. Of course, we can't say so because there is no control and there are many confounding factors. But I offer the following for consideration.
1. Atmospheric testing was a massive propaganda tool and an excellent way of developing weapons. It is now banned and never done even by lunatics like the North Koreans. Why?
2. Cancer rates have increased substantially in the period - this is not evidence of causality, but if they had not then we could say that it would be evidence of absence of causality.
3. There is not much mention of this ever in the media.
4. There is not much to be done about it now.