The detonation of the first thermonuclear device projected the problem of environmental contamination to the stratosphere and, literally, to every part of the earth. This explosion, Test Mike, largest on earth to that time, was set off on Elujelab Island, on the north rim of Eniwetok Atoll, on November 1, 1952. In the reef where Elujelab had been, the blast left a crater almost a mile in diameter and 200 feet deep. The towering nuclear cloud rose in 15 minutes to a height of 130,000 feet. Test Mike marked a point of change. Before, fallout from nuclear detonation had been principally local, touching the waters and reefs of an atoll or a desert landscape. After Test Mike, the implications of fallout obviously were global. A mishap in connection with a 1954 thermonuclear test at Bikini contributed in two important ways to the enlargement of environmental investigations. Fallout from the test, swept off its predicted pattern by unexpected winds at high altitudes, deposited debris on Rongelap, an inhabited atoll east of Bikini, and on fishermen aboard a Japanese vessel operating in the Bikini-Rongelap area. The accident, unfortunate in its consequences at Rongelap and in Japan, had other results of even wider impact. From it came the first international approaches to the problems of ocean contamination and, later, long-term bioenvironmental studies at Rongelap itself. [Illustration: _School of surgeonfish off Arji Island, Bikini Atoll, August 1964. Note coral growth on lagoon bottom._] Wide-ranging studies of ocean-borne radioactivity were initiated by the Japanese. The experience of the fishermen produced in Japan a fear of contamination of fisheries resources as a result of the United States tests. One result was the organization, in the summer of 1954, of a government-sponsored ocean survey expedition that cruised from Japan into and through the Bikini-Eniwetok area to determine what amounts of radioactivity were being carried, by water and by aquatic organisms, toward the shores of Japan. The expedition made significant observations of the role of plankton[10] in the biological utilization of ocean fallout. A United States scientific team, following up the Japanese effort, made a similar but far more extensive cruise through the Western Pacific early in 1955 and went on to Japan to discuss its findings with the Japanese. During and after the test series in the Pacific in 1956 and 1958, United States surveys of the ocean were made routinely. Exchanges of information between scientists of Japan and the United States continued. The Rongelap case produced results of another kind. The Rongelap people were found to have suffered exposure requiring medical attention and continued observation. Evacuated from their atoll because it was not safe, members of the community were given care at other atolls until they could be repatriated in 1957, and received continued medical supervision thereafter.