One of the most devastating tests was the so-called Operation Castle Bravo, launched on Bikini Atoll on 1st March,1954, inwhich a hydrogen bomb, with a power of 15 megatons, 1,000 times higher than that of the Hiroshima bomb, was detonated. The Bravo operation had serious consequences since the winds carried a radioactive ash shower over the atolls of Rongelap, Ailinginae and Utrik. Since the operation had been secret, the 236 inhabitants of those islands had not been evacuated and, as a result, were irradiated.
Approximately five hours after the explosion of the bomb, the radioactive rain began to fall on the inhabitants of the islands. Those people, who knew nothing of what had happened, saw a fireball on the horizon and, hours later, ash began to rain down, forming a layer a few centimetres thick. Some hours later they would begin to experience the physical signs of exposure to radiation in the form of vomiting, diarrhoea and hair loss.Bolet generat per l’explosió nuclear de l’operació Castle Bravo a l’atol de Bikini, a les Illes Marshall. Fotografia: US air force
One of the witnesses, who was 14 years old at the time of the explosion, explained to the United Nations Human Rights Council in 2012 : "I was playing when the poisonous waste of the bomb fell on me. I didn't know what it was but because it seemed like snow I started playing with it. But suddenly my eyes and mouth burned. Later, at night, I was very ill. All the people on the island were very ill, especially the children. The next day, my skin was cracked and covered with sores. I had burns on my skin and was in a lot of pain. My hair started to fall out. After two days of drinking contaminated water, eating contaminated food and breathing contaminated air, we were evacuated by the United States ... "
It was not until 50 hours after the explosion that the United States Navy transferred people to the Kwajalein Atoll to receive medical attention. The inhabitants of Utrik returned to their homes months later, but those of Rongelap could not do so for three years.
Between 1954 and 1957, the people of Rongelap lived first on the island of Ebeye, then on Kwajalein and then later on the island of Ejit, in Majuro Atoll, under circumstances of deprivation, hardship and anguish for the loss of their homes. In 1957, they were informed through the Atomic Energy Commission of the United States Government that it was safe to return to Rongelap and, in June of that year, they were returned to the island with the warning to not eat the food that grew there. In spite of everything, the inadequate and infrequent supply caused many of the inhabitants to ignore this warning.
According to other witnesses, in the subsequent years some of those exposed to the pollution died and others developed several types of cancer. The witnesses also speak of a high number of abortions and of children who were born with malformations. Some of those affected were subject, over a period of decades, to a secret medical research program whose purpose was to obtain valuable data on the delayed effects of radiation on people .
In 1982, the US Department of Energy published the results of a radiological study of the northern islands that suggested that the radioactive contamination in Rongelap was still high and that, therefore, it was not a safe place to live. In subsequent years, the inhabitants of Rongelap were relocated again, principally to the island of Mejatto in the Kwajalein Atoll. In 1999, the project to clean and rehabilitate the island began, in order make it habitable once again.
 Environment, health, and other human rights concerns associated with nuclear weapons testing (…) Submission to the United Nations Universal Periodic Review of the Republic of theMarshall Islands. Second Cycle. Twenty Second Session of the UPR Human Rights Council. April - May 2015