Government scientists who blew up two atomic bombs on the sands of the Nevada desert during the early Cold War were well aware that the fallout could have harmed civilians. Secret documents released by a presidential commission today quote scientists describing the health risk as a necessary "gamble." The1951 Defense Department project sought to study the effects of radioactive fallout -- despite the fact this meant using American citizens as the lab animals. The ground-level explosions were followed by above-ground blasts that continued until the early 1960s. Natural Resources Defense Council historian Stan Norris told TIME Daily that the ground-level nuclear tests "kicked up a huge amount of dirt." Norris says although "downwind" Utah and Nevada residents blame the tests for high cancer rates in their towns, the government disagrees. Despite years of legal wrangling, he notes, the dispute remains unresolved.