Project 4.1
In 1994, a 1953 "Castle Bravo" program prospectus was found which included reference to Project 4.1 apparently written before the "Bravo" shot had occurred. The U.S. government responded that someone had gone back into the project list after the "Bravo" test to insert Project 4.1; thus, according to the U.S. government, the acts were not premeditated. All other U.S. documents point to Project 4.1 having been established after the "Bravo" test—most sources point to its having been organized on March 7, 1954. The final Project 4.1 report began in its preface with the statement that "Operation CASTLE did not include a biomedical program" (it mentions this in discussing the ad hoc nature by which the project personnel were assembled). All official and mainstream historical accounts of the "Bravo" test indicate that its high level of fallout was a result of a miscalculation in relation to its design and was not deliberate (see the Castle Bravo article for more information on the alleged accident).
Nuclear testing at Bikini Atoll
On the Marshall Islands, the detonation of Castle Bravo was the cause of most of the radiation exposure to the surrounding populations. The fallout levels attributed to the Castle Bravo test are the highest in history. The exposure to fallout has been linked to increase the likelihood of several types of cancer such as leukemia and thyroid cancer. The relationship between I-131 levels and thyroid cancer is continuing to be researched. There are also correlations between fallout exposure levels and diseases such as thyroid disease like hypothyroidism. Populations of the Marshall Islands that received significant exposure to radionuclides have a much greater risk of developing cancer. The Castle Bravo test detonation produced an explosion of approximately 15 megatons, which is about three times its predicted value. Populations neighboring the test site were exposed to high levels of radiation resulting in mild radiation sickness of many (nausea, vomiting, diarrhea). Several weeks later, many people began suffering from alopecia (hair loss) and skin lesions as well. The female population of the Marshall Islands have a sixty times greater cervical cancer mortality than a comparable mainland United States population. The Islands populations also have a five time greater likelihood of breast or gastrointestinal mortality, and lung cancer mortality is three times higher than the mainland population. The male population on the Marshall Islands lung cancer mortality is four times greater than the overall United States rates, and the oral cancer rates are ten times greater.