to the exposure, (if they became evident). These medical activities did, in fact, uncover and document an unexpected incidence of both benign thyroid nodules and thyroid cancer. 5.4 Factors Limiting Epidemiological Studies of Exposed Marshall Islands Population The medicalactivities provided the Marshall Island population would not be expected to be of value for effectively evaluating (measuring) the dose-response relationships between exposure and disease or to test hypotheses in this regard. The problems detailed in this section preclude (prevent) effective application of the information for this purpose. Briefly these problems include: the lack of individualized exposure measurementor estimation, unknown rates of naturally occurring disease in this population, the small numberofindividuals exposed, lack of preexisting formal birth, death and other vital records, and the inability to define a comparable unexposed control population. In addition, the victims of the radiation incident did not, and are not likely to continue to appreciate being perceived as experimental subjects. Specific problems are discussed below: 5.4.1 Incomplete population identification . The total exposed population may not have been completely identified and the control population selected may have included individuals with some exposure. Rongelap, Ailingnae, Utirik and Rongerik (U.S. servicemen) were exposed atolls. In early studies these were selected as exposed because they were "nearby" and inhabited, and thought to be downwind of Bikini, the test site. However, several other islands also may have received fall-out. The following are data (severaljustifications for) that support this supposition: 32