Additional follow-up checks on the Marshallese studied in Project 4.1 were conducted at regular intervals afterwards every year since 1954. Though the Marshallese experienced far milder immediate effects than the Japanese fishermen exposed to Bravo fallout on the fishing boat Daigo Fukuryū Maru, the long-term effects were more pronounced as they depended largely on subsistence living and were relocated to the site of the testing in Bikini, Ene Wetak, and Rongelap while the Japanese fisherman were returned to Japan. For the first decade after the test, the effects were ambiguous and statistically difficult to correlate to radiation exposure: miscarriages and stillbirths among exposed Rongelap women doubled in the first five years after the accident, but then returned to normal; some developmental difficulties and impaired growth appeared in children, but in no clear-cut pattern. In the decades that followed, though, the effects were undeniable. Children began to disproportionately develop thyroid cancer (due to exposure to radioiodines), and almost a third of those exposed developed neoplasms by 1974.
