Similar but less severe hematologic alterations were observed in the group receiving intermediate radiation doses on Ailingnae, whereas the lowexposure group on Utirik did not develop significant alterations of any blood elements except for a slight transient depression of platelets noted only on analysis of the entire population at four weeks post-exposure. Despite thrombocytopenia and neutropenia in the heavily irradiated group, bleeding tendencies and increased susceptibility to infection were not observed. Even during the nadir of neutropenia, individuals were still able to respond to an outbreak of upper respiratory infections by increasing leukocyte outputs. Clinical sequelae of these hematologic effects were not ob‘served except for one fatal case of acute myeloblastic leukemia in 1972 in a young man who was one year old at the time of exposure. This may well represent a long-term hematologic effect of radiation. D. Dosimetric Evaluation 1. Early Radiation A number of caveats should be applied to interpretation of certain data within this and previous reports. These apply principally to radiation dose estimates and dose/effect correlations, especially regarding radiation induction of thyroid neoplasms as discussed in Section IX.C.1l. Since the initial incident created an emergency of unparalleled and unanticipated proportions, data acquisition was necessarily secondary to exigencies of evacuation, decontamination, and care of those affected. Further, the task force was unprepared for gathering extensive dosimetry data or analyzing radiochemical characteristics of the fallout in the actual areas of deposition, since these were quite remote from the areas predicted. Accurate dosimetry was hindered by a large number of variables: 1. Radiation monitoring teams and equipment were concentrated at a distance in areas of predicted fallout, and no monitoring personnel were in the vicinity of the atolls actually affected. 2. The time of arrival of fallout at each point and its duration could be estimated only by visual observations of the particulate debris, by the re- corder of a single low-level gamma detector at the weather station on Rongerik, and by calculations based on meteorological data and fallout predic- tion models. 3. Actual gamma dose-rate measurements on each island were made by ANPDR/39A survey meters but not until the times of evacuation, 50 to 78 hours after the detonation. 4. Quantitative measurements of short-lived radioisotopes, especially those of iodine (13317, 1347, 1351) were not obtainable. 5. The possibility of chemical fractionation within the cloud and consequent production of localized concentrations of specific radioisotopes was also not measurable. 6. The complex radiation spectra of isotopes comprising mixed fission product fallout produced gamma energy peaks in the regions of 0.1, 0.7, and 1.5 MeV, variably affecting midline depth doses. 7. The distribution of fallout debris on the ground, roofs, trees, and body surfaces produced an exposure geometry unlike any experienced previously