6 IRON-Sy RONGELAP PEOPLE, FISH AND SO)...’ March 1970, and Fig. 1 shows a frequency distribution of the body burdensof males and Disintegration rates of 55Fe in the samples were determined by comparison with ®5Fe electrodeposited from a standard solution obtained from the National Bureau of Standards. females. The Rongelapese which were included 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% (2c) confidence level. Not all donors were weighed in 1970, therefore body weights from previous years were used to compute total blood volumes. However, weights from previous years applied ‘mostly to younger conors. Since weight generally increases with age, some individual esti- Correction was made for the self-absorption of the X-rays in the electrodeposited iron. Stable _ iron was determined colorimetrically, using ophenanthroline as the color-forming agent.) Body burdens were estimated byfirst measuring the *5Fe in a known volume of blood (4— 26 mJ); Total blood volume was estimated using body weight and average blood volumes of 82 ml blood per kg body weight for males and 74 ml biood per kg body weightfor females. The iron content of blood was assumed to be mates of 5°Fce body burdens, and therefore the 65% of the total body iron. This method of averages shown in Table 1, are likely to be calculating total blood volume is that used by conservative. Persson”*) in his estimate of ®5Fe body burdens The maximum body burden in the males in Lapps of Northern Sweden. Previousesti- was 0.85 uCi, while 3 females had body burdens mates of body burdens from composite blood greater than this value. The maximum obspecimens"-5) were made assuming that the served female body burden was 1.0 pCi, average total blood volume -was 51. and that Table 1. Average ™¥Fe body burdens of Rongelapese 60 & ofthe totaliron is in the blood. Using this method with the Rongelap data, the average Date 55Fe 53Fe body burdens agreed within 15% of those sampled No. of subjects/sex (uCi)* calculated using body weights. . March 1970 March 1970 RESULTS AND DISCUSSION Table 1 gives the average body burdens of 55Fe in the group of Rongclapese sampled in 10+ MALES 28/M 32/F 0.43 + 0.17 0.40 + 0.27 * Standard error (lo) of the mean. 4 , FEMALES 84 wy sow a f , T7 5 2 6Q eR ‘a 2 al cs s 3 a iS > : A Bf ; 5! 5 5 = qf 2- 4 1 ot oO 0.20 EE O40 = oOs0 : = 080 | 0 ONOSAhe Pe Os aS TE eePers oh 94 a] a GB "i . Py é ca AS] x i? 020 SSFe body burdens (pCi) O40 k 060 : yk 080 >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 *Fe body burdens between 0.10-0.20 wCi while nine females had 55Fe body burdens in the sameactivity interval.