CHAPTER 5 INTERNAL RADIOACTIVE CONTAMINATION §.1 PREVIOUS FINDINGS Following the contaminating event, high levels of activity were fourid in drinking water and on the external surface of plants on the contaminated atolis, Gross beta activity was found in. the urine of the majority of Rongelap and Ailinginae inhabitants, with an average of 12038 dis/min/24 hr for the Rongelap and 553 dis/min/24 hr for the Allinginae groups 6 weeks after exposure. The excretion rate of radioactivity was found to be three times as great in adults 18 was found in the 0 to 5 year old age group. Strontium, barium, and the rare earth group together contributed 75 per cent of the total beta activity of the urine at this time. The degree of internal radiation hazard was considered too low to have contributed significantly to the acute effects observed following exposure. , §.2 METHODS Twenty-four hour urine specimens were obtained for analysis by the U.S. Naval Padiological Defense Laboratory (NRDL), Chemical Technology Division, and by the New York Operations Office of the Atomic Energy Commission. Methods of analysis have been described previously.! §.3 RESULTS ey Of 53 urine specimens obtained from the Rongelap and Ailinginae groups and analyzed by the NRDL Chemical Technology Division, cetectable gross beta activity was found only in 3ix patients, all of whom were in the Kongelap group, and only one of whom was over 12 years of age. Counts ranged from 6 to 90 dis/min/24 hr. Barely detectable radioactivity was found in 23 urine specimens analyzed by the New York Operations Office. REFERENCE « 1, E. P. Cronkite et al., Study of Respo:se of Human Beings Accidentally Exposed to Significant Fallout Radiation, Operation Castle final report of Project 4.1. $5