sentences:  Until November 1962, the vast majority of U.S. nuclear tests were aboveground.After the acceptance of the Partial Test Ban Treaty, all testing was regulated underground, in order to prevent the dispersion of nuclear fallout.As of February 2006, over $1.2 billion in compensation was paid to U.S. citizens exposed to nuclear hazards as a result of the U.S. nuclear weapons program, and by 1998, at least $759 million was paid to the Marshall Islanders in compensation for their exposure to U.S. nuclear testing.