ee 3 246 IRON-55 IN RONGELAP PEOPLE, FISH AND SOILS Disintegration rates of 55Fe in the samples were determined by comparison with 55Fe electro- March 1970, and Fig. 1 shows a frequency distribution of the body burdens of males and females. The Rongelapese which were included deposited from a standard solution obtained from the National Bureau of Standards. Correction was made for the self-absorption of the X-rays in the electrodeposited iron. Stable iron was determined colorimetrically, using o- in this study consisted entirely of those individuals who were subjected to external radiation in 1954. Iron-55 levels in the blood samples were sufficiently high to permit count rate measurements to +5°%at the 95% (20) confidence level. Not all donors were weighed in 26 ml). Total blood volume was estimated using body weight and average blood volumes of 82 ml blood per kg body weight for males were used to compute total blood volumes. However, weights from previous years applied mostly to younger donors. Since weight gener-~ phenanthroline as the color-forming agent.10 Body burdens were estimated byfirst measuring the 55Fe in a known volume of blood (4— 1970, therefore body weights from previous years ally increases with age, some individual estimates of 55Fe body burdens, and therefore the averages shown in Table 1, are likely to be and 74 ml blood per kg body weightfor females. The iron content of blood was assumed to be 65% of the total body iron. This method of calculating total blood volume is that used by Persson"?) in his estimate of 55Fe body burdens in Lapps of Northern Sweden. Previousestimates of body burdens from composite blood specimens"™-5) were made assuming that the conservative. The maximum body burden in the males was 0.85 wCi, while 3 females had body burdens greater than this value. The maximum ob- served female body burden was average total blood volume was 51. and that 1.0 4Ci, 60 % of thetotal iron is in the blood. Usingthis method with the Rongelap data, the average Table 1. Average Fe body burdens of Rongelapese calculated using body weights. sampled 58Fe body burdens agreed within 15% of those Date - March 1970 RESULTS AND DISCUSSION 104 MALES » (xCi) 0.43 + 0.17 32/F 0.40 + 0.27 * Standard error (1c) of the mean. J 94 28/M March 1970 Table 1 gives the average body burdens of 53Fe in the group of Rongelapese sampled in 55F . No. of subjects/sex FEMALES » , a ~ a § 5 4 Nn 44 4 $* ] 14 4 a 3 24 O- Qo 0.20 040 O60 +e O08 0 020 S5Fe body burdens (uCi) 040 9060 0.80 : >0.90 Fic. 1. Frequency distribution of °5Fe body burdens in Rongelap males and females. Body burdens have been grouped into classes, Example: 3 Rongelap males had 5*Fe body burdens between 0.10~0.20 pCi while nine females had “Fe body burdens in the same activity interval. aT