The Tribunal accepted evidence from several witnesses on the long-term effects of nuclear weapons in terms of low-level radiation and the human body. One, Dr. Glenn Alcalay, concentrated on long-term medical effects experienced by inhabitants of the Marshall Islands in the Pacific where a large number of American nuclear tests were conducted in the 1950s. This evidence was particularly revealing as it concerned the effects on populations who were not direct or intended victims of nuclear attack. In a written report, Dr. Alcalay revealed that on several occasions the Marshall Islanders were subjected to accidental radioactive contamination from fall-out. In one particular 15 megaton detonation, the BRAVO test of March 1954, a total of fourteen islands was affected. Three days after the explosion (at Bikini Atoll) the inhabitants of Kongelap Island were evacuated by the US Navy. They were returned to the island in 1957 but began to experience medical problems. On several occasions women gave birth to "creatures like monkeys, some like octupi, and some like bunches of grapes". A few years later other islanders were found to be suffering from thyroid problems and leukaemia . Dr. Alcalay's report notes that the long-term effects on the islanders eventually included late-occurring thyroid effects including tumours and thyroid dysfunction with concomitant growth abnormalities, as well as blood changes and chromosome aberrations, adverse birth outcomes and the effects of ecosystem contamination and the uptake of radionuclides in the food-chain. The Tribunal noted with concern that his report indicated that data from the Marshall Islands suggests that low levels of ionizing radiation may cause as much cancer as higher levels over a long period of time. A group exposed to a whole-body gamma dose of 14 rads (considered by many experts to be insignificant) appears to have experienced the same rate of thyroid cancer as a group exposed to 175 rads.