“re we oe ‘ag 4 oy CHAPTER 5 INTERNAL RADIOACTIVE CONTAMINATION 5.1 INTRODUCTION A study of the nature and extent of the internal radioactive contamination in the exposed human beings was initiated on the 16th day post-detonation, with the collection of 24-hour urine samples from the Rongelap, Ailinginae and American groups. Additional information on the extent and nature of the radioactive contamination was obtained from domestic animals, foodstuffs, water and soil collected on the contaminated atolls and sent to the U. S. Naval Radiological Defense Laboratory, the Naval Medical Research Institute, the New York Operations t5 i. i Office of the Atomic Energy Commission, and the Los Alamos Scientific Laboratory for gross activity measurements and radiochemical analyses. Data on soil, water, and plants were a necessary to determine the feasibility of utilizing the foodstuffs and living area of the contami- nated atolls, Long term studies of the domestic animals obtained are being conducted at the NRDL, in order to obtain information on the p ssible acute and delayed hazard from internal * radiation, The main findings of the internal contamination study in the human beings and their environment are presented in this report, A detailed report on the nature and extent of the inz - ternal radiation hazard in human beings and animals, as well as the contamination of the environment will be presented in an addendum report. 5.2 PHYSICAL ENVIRONMENT STUDIES A comparisonof the food, water and soil samples from Rongelap, Utirik and Rongerik indicated a much higher level of contamination on Rongelap than on the other islands. The activity appeared to be distributed in the same manner on all the islands. In general, the con- tamination was associated with very fine particulate matter and was uniformly distributed throughout samples of earth, thatch, and grass. Significant amounts of beta activity (1 uc per plant) as well as fissionable material (1 x 1074 ygm) were present on the external surfaces of plants at 42 days, but only small amounts of beta and no alpha activity were detected in the edible portions, Coconut tree sap, an important item in the native diet, was found to have beta activities of the level of 1 uc,liter on Rongelap at two months after detonation. Fish collected from the Rongelap lagoon were found to have very high levels of activity (0.3 to 3 pc per fish) as late as 120 days post-detonation. The activity found in soil was determined to be associated mainly with fallout particles of relatively large diameter. Rongelap water samples from both cisterns and a well (Figs. 5.1 and 5.2) had activities of about 1 uc,liter at 30 days. Samples of thatch roofing exhibited the highest levels of activity in the physical environment. The presence of fissionable material was detected on thatch, grass and on plant food. sw eeenge peer + oe ates betes OF ° . Boe wares ene wavere oe . 2 oo . oe onenve 89