16 EFFECTS OF IONIZING RADIATION of Group II (Ailinginae), 5 percent of Group III (Americans), and none of Group IV (Utirik). Three people in Group I and one in Group I complained of itching and burning of the eyes and lacrimation. These initial skin and eye symptoms were most likely due to irradiation since all individuals who experienced the initial symptoms later developed unquestioned radiation induced skin lesions (epilation and conjunctivitis). (See Chapter IIT.) Furthermore the initial symptomatology in these people was similar to that reported in instances of accidental laboratory overexposure to radiation, described in Chapter ITI. It is possible, however, that chemical irritation by the fallout material, which was predominantly highly alkaline calcium oxide, may have accentuated the initial symptoms. About two-thirds of Group I were nauseated during the first 2 days and one-tenth vomited and had diarrhea. One individual in Group II was nauseated. In Groups III and IV there were no gastrointestinal (GI) symptoms. The information concerning symptomswas obtained by questioning through an interpreter by several individuals. Despite the repeated interrogations and the inevitable suggestions of the interrogators, the stories remained consistent. All GI symptoms subsided by the third day without therapy and there was no recurrence. The presence, severity, and duration of nausea, vomiting, and diarrhea are known to bear a direct relationship to degree of exposure and probability of the recovery (1, 2, 6), and it is of note that the incidence of these symptoms was correlated with the dose received and that there were no gastrointestinal symptoms in Group IV, the largest group, which received only 14 r. GI symptomatology may have been due to direct injury of the GI tract as observed in animals after whole body irradiation (7, 8) or may have been non-specific as is observed following therapeutic radiation. Various other clinical conditions, which were encountered during the course of observation of the exposed groups were not the results of radiation exposure. The incidence and type of disease seen, discussed below, were similar in all exposure groups and in nonexposedindividuals. 2.3 Clinical Observation and Therapy With Respect to Hematological Findings 2.31 Clinical Observations and Leukocyte Counts Berween Tue 38rd and 48rd post-exposure days, 10 percent of the individuals in Group I had an absolute granulocyte level of 1000 per cubic millimeter or below. The lowest count observed during this period was 700 granulocytes/ mm.* During this interval the advisability of giving prophylactic antibiotic therapy to granulocytopenic individuals was carefully considered. However, prophylactic antibiotic therapy was not instituted for the following reasons: (1) All individuals were under continuous medical observation so that infection would be discoveredin its earliest stages. (2) Premature administration of antibiotics might have obscured medical indications for treatment, and might also havelead to the development of drug resistant organisms in individuals with a lowered resistance to infection. (3) There was no accurate knowledge of the numberof granulocytes required by manto prevent infection with this type of granulocytopenia. The observed situation was not strictly comparable to agranulocytosis with an aplastic marrow as seen following known lethal doses of radiation. In the latter instance, granulocytes fall rapidly with practically none in circulation and no evidence of granulocyte regeneration when infection occurs (6). In the present group of individuals exposed to radiation, most counts reached approximately one-fourth the normal value, but the fall to that level was gradual and the presence of immature granulocytes in the peripheral blood during the pe-