90-foot (30-meter) underwater test at Bikini Atoll, central Pacific, 1946, eight years before the Castle Bravo test

Photo courtesy Los Alamos National Laboratory, Atomic Archive

Atmospheric and Underwater Testing

Atmospheric tests release all the radioactive fallout of a nuclear bomb exploding in mid-air or on the surface of the ground. In these tests, the nuclear   device may be fixed atop a tower, dropped from a plane or carried into the atmosphere by a balloon.

Tremendous amounts of fallout result from these tests, and the safety measures in place to prevent damage to humans, animals, crops, buildings, ecosystems and everything else within a radius of hundreds of miles involves clearing the area, pure and simple. 

Nuclear tests are normally carried out in desolate areas like the Nevada desert, where damage from the fallout can be reduced because there is so little life in the area. Still, the biggest nuclear-testing disaster in U.S. history was an atmospheric test in which engineers had taken all necessary precautions. Unfortunately, it turns out they took all the necessary precautions for a much smaller-yield bomb.

The Castle Bravo test in 1954, conducted on a man-made island in the Pacific Bikini Atoll, far exceeded expectations. The explosion was twice the size the U.S. had expected, and the radioactive fallout was far greater than predicted. When weather patterns changed, the wind carried this mass of radioactive particles into areas that had not been evacuated before the test. Island populations that were not supposed to be subject to any damage at all ended up with radiation burns, high cancer rates and next-generation birth defects that most experts attribute to Castle Bravo. In broader terms, the high number of atmospheric tests performed by France in the 1960s and '70s appears to have led to three times the rate of thyroid cancer and four times the rate of acute myeloid leukemia in French Polynesia than in other comparable populations not in the vicinity of extensive nuclear testing.

Underwater testing carries a lot of the same risks at atmospheric testing, since the explosion rises well out of the water. But the amount of radioactive fallout in the atmosphere is decreased because a good portion of it is contained in the water. This causes its own problems, of course.

While effects of underwater testing on sea life have been surprisingly absent from most literature, environmental groups document complete destruction of coral reefs and death and contamination of other marine life as resulting from these tests. By extension, fishing villages and their seafood-subsisting populations can be severely affected by underwater nuclear tests conducted hundreds miles from their shores.

Read on to learn about two more types of nuclear testing.