Uploaded April 2013 | Updated September 2026, 14 hours ago
From 1945 to 1980, over 500 weapons tests were conducted in the atmosphere at a number of locations around the world. These tests resulted in the release of substantial quantities of radioactive debris to the environment. Local, intermediate, and global fallout deposition densities downwind from test sites depended on the heights of bursts, the yields, and the half-lives and volatilities of the particular fission or activation products, as well as on the meteorological conditions. After Hiroshima and Nagasaki, fear of the radiation effects of nuclear weapons grew, but it was the hydrogen bomb tests of the mid-1950s that made nuclear "fall-out" into a world-wide issue. Particularly important was the United States' "BRAVO" test of March 1, 1954. The bomb was twice as powerful as planned and radioactive dust fell on the natives of Rongelap Atoll and on the Japanese fishing vessel, theLucky Dragon No. 5. When the boat returned to Japan two weeks later, the crew was suffering from the classic effects of radiation sickness. One crew member died. The Lucky Dragon incident profoundly shocked Japan. A panic broke out about the possible radioactive pollution of tuna fish. In America, many were angered by government denials that radiation had anything to do with the fishermen's illness. The radioactive cloud usually takes the form of a mushroom, that familiar icon of the nuclear age. As the cloud reaches its stabilization height, it moves downwind, and dispersion causes vertical and lateral cloud movement. Because wind speeds and directions vary with altitude, radioactive materials spread over large areas. Large particles settle locally, whereas small particles and gases may travel around the world. Rainfall can cause localized concentrations far from the test site. On the other hand, large atmospheric explosions injected radioactive material into the stratosphere, 10 kilometers or more above the ground, where it could remain for years and sub sequently be deposited fairly homogeneously ("global" fallout). Nuclear tests usually took place at remote locations at least 100 kilometers from human populations. In terms of distance from the detonation site, "local fallout" is within 50 to 500 kilometers from ground zero, "regional fallout" 500--3,000 kilometers and global fallout more than 3,000 kilometers. Because the fallout cloud disperses with time and distance from the explosion, and radioactivity decays over time, the highest radiation exposures are generally in areas of local fallout. Following the deposition of fallout on the ground, local human populations are exposed to external and internal irradiation. For more on the issues of fallout cancer.gov/PublishedContent/Files/cancertopics/causes/i131/fallout.pdf. This is clipped from a Universal-International newsreel from May 30, 1957.
From 1945 to 1980, over 500 weapons tests were conducted in the atmosphere at a number of locations around the world. These tests resulted in the release of substantial quantities of radioactive debris to the environment. Local, intermediate, and global fallout deposition densities downwind from test sites depended on the heights of bursts, the yields, and the half-lives and volatilities of the particular fission or activation products, as well as on the meteorological conditions. After Hiroshima and Nagasaki, fear of the radiation effects of nuclear weapons grew, but it was the hydrogen bomb tests of the mid-1950s that made nuclear "fall-out" into a world-wide issue. Particularly important was the United States' "BRAVO" test of March 1, 1954. The bomb was twice as powerful as planned and radioactive dust fell on the natives of Rongelap Atoll and on the Japanese fishing vessel, theLucky Dragon No. 5. When the boat returned to Japan two weeks later, the crew was suffering from the classic effects of radiation sickness. One crew member died. The Lucky Dragon incident profoundly shocked Japan. A panic broke out about the possible radioactive pollution of tuna fish. In America, many were angered by government denials that radiation had anything to do with the fishermen's illness. The radioactive cloud usually takes the form of a mushroom, that familiar icon of the nuclear age. As the cloud reaches its stabilization height, it moves downwind, and dispersion causes vertical and lateral cloud movement. Because wind speeds and directions vary with altitude, radioactive materials spread over large areas. Large particles settle locally, whereas small particles and gases may travel around the world. Rainfall can cause localized concentrations far from the test site. On the other hand, large atmospheric explosions injected radioactive material into the stratosphere, 10 kilometers or more above the ground, where it could remain for years and sub sequently be deposited fairly homogeneously ("global" fallout). Nuclear tests usually took place at remote locations at least 100 kilometers from human populations. In terms of distance from the detonation site, "local fallout" is within 50 to 500 kilometers from ground zero, "regional fallout" 500--3,000 kilometers and global fallout more than 3,000 kilometers. Because the fallout cloud disperses with time and distance from the explosion, and radioactivity decays over time, the highest radiation exposures are generally in areas of local fallout. Following the deposition of fallout on the ground, local human populations are exposed to external and internal irradiation. For more on the issues of fallout cancer.gov/PublishedContent/Files/cancertopics/causes/i131/fallout.pdf. This is clipped from a Universal-International newsreel from May 30, 1957.
