What means were used to discourage the questioning of american leaders about a-bomb effects?

The A-bomb was supposed to have horrible effects on Hiroshima and Nagasaki-that was the whole point. I think you need to look at what was decided at Yalta to understand why they did what they did. The issue of worker safety at Hanford is a different question. Certainly the compartmentalization of information played a factor in Manhatten project related accidents. We are talking about an era when workers handled asbestos with no special precautions. If anything, Hanford was probably less likely to kill off its own workers than the average shipyard at the time.