“a —'4 whe 12 7 |432 1Q\- aig L ® * 2 4 4 4 81- mo BN . aL | - + ee a | . T 2b 5 —~8 a wn o | | Lo 5 Log —72 20 . . so ol, a -! . ~ “oe . : 78 wo. . 4 | . a "+42 “ 2.5 BAIB mg CREATININE Figure 47. Urinary BAIB excretion (mg-8-amino-:so- butyric acid per mg creatinine) versus body load of Cs'** (uC), Rongelap inhabitants, 1959. 0.06; unexposed, 2.10220.04). A scatter plot of Cs*** levels and BAIB levels shows no correlation (Figure 47), and neither does a similar plot between Zn** levels and BAIB levels. The mean BAIB excretion level for 18 Micronesians, who were on Utirik at the time of the atomic explosion and therefore not exposed to significant radiation, was 2.21 0.13, which is extremely close to the mean value for the Rongelapese. Among the Uti- rik people 83% were high excretors, which is not significantly different from the Rongelap group percentage. A numberof complete families are included in the Rongelap sample (i.e., father, mother and at least onechild); of these the high- excretor by high-excretor matings-are the only ones providing significant genetic information. There were 11 such matings with a total of 31 offspring (29 high excretors and 2 low excretors). One of the low excretor offspring wasillegitimate, as determined by blood group data, but the otherre- mains as an unexplained exception to genetic hypothesis. Rubini et al.** have recently demonstrated thar # BAIB in man ***3 and excreted in urine, since no appreciable tubular reabsorption of BAIB 6ccurs.** It is unlikely that the high incidence of high BAIB excretors found in Rongelap is due to radiation. The identical average BAIB valuesin the ex- posed and unexposed groups preclude the possibility that the elevation is due to thefallout exposure in 1954, and it appears that radiation ex- - posure (at the levels received at Rongelap) has no long-term effect on BAIB excretion. Thelack of correlation with the Cs'*? and Zn*® body burdens rules against the elevation being due to the present retained internal radiation. The nearly identical values in the Utirik group who received a very small dose of radiation, and who have much lower body burdens of radionuclides, is also consistent with the thesis that a high incidence of the gene underlying $-amino-ise-butyric aciduria is responsible for the observed BAIB excretion rate. The expression of the norma! genetic differenceis probably due to differential metabolism of BAIB by high and lowexcretors.** The level of BAIB excretion among the Mar- BAIB excretion can be a sensitive indicator of shallese is the highest yet reported for any popula- nitrogen mustard on BAIB excretion.*? Such origin; if this is true, a high BAIB level can be radiation exposure. The mechanism involved is - probably the sameas that underlying the effect of agents markedly increase DNA breakdown; the thymine thus released is effectively converted to tion. Blood group*®® and other anthropological data on these people suggest a Southeast Asiatic predicted for the populations of that region. Studies of some Asiatic populations have given