Castle Bravo
The decision to carry out the Bravo test under the prevailing winds was made by Dr. Alvin C. Graves, the Scientific Director of Operation Castle. Graves had total authority over detonating the weapon, above that of the military commander of Operation Castle. Graves appears in the widely available film of the earlier 1952 test "Ivy Mike", which examines the last-minute fallout decisions. The narrator, the western actor Reed Hadley, is filmed aboard the control ship in that film, showing the final conference. Hadley points out that 20,000 people live in the potential area of the fallout. He asks the control panel scientist if the test can be aborted and is told "yes", but it would ruin all their preparations in setting up timed measuring instruments. In Mike, the fallout correctly landed north of the inhabited area but, in the 1954 Bravo test, there was a large amount of wind shear, and the wind that was blowing north the day before the test steadily veered towards the east.
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.