The term fallout refers to the radioactive debris produced by a nuclear explosion that settles to the surface of the earth. A nuclear explosion produces four types of radiation—gamma radiation, beta radiation, alpha radiation, and neutrons. Most of the radiation is spread via soil and debris carried upward in the mushroom cloud, which then falls over a wide area. These radioactive materials can severely damage people, animals, and plant life. Symptoms of radiation sickness are headaches, fever, thirst, dizziness, loss of appetite, lethargy, nausea, diarrhea, vomiting, hair loss, discoloration of fingernails, hemorrhaging, and burns. Long-term effects include various cancers, particularly leukemia. Early tests of nuclear weapons proved that radioactivity was a problem, but scientists and administrators from the Atomic Energy Commission (AEC) were able to short-circuit publicity until incidents from radioactive fallout became too common. Scientists also learned that rain intensified radioactive fallout, so they were careful to schedule tests in areas and times of clear weather. Unfortunately, sometimes rain showers several days later would produce radioactive hot spots around the country.
The magnitude of the problem of fallout surfaced during the Upshot-Knothole tests at the Nevada Testing Site in 1953. Reports reached the AEC about animals suffering side effects of radiation and dying. Veterinarians were called in, and they identified the problem as iodine-131. Iodine-131 is one of the radioactive elements produced during fission and has a half-life of eight days. In both humans and animals, iodine-131 is stored in the thyroid gland. This report was sent to AEC authorities, who had the report rewritten and then ignored it. Moreover, the authorities refused to pay damages for the loss of animals.