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mg CREATININE
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“42
25
DOE ARCHIVES
Figure 47. Urinary BAIB excretion (mg-8-amino-iso-butyric acid per mg
creatinine) versus body load of Cs’™ (uC), Rongelap inhabitants, 1959.
0.06; unexposed, 2.10+0.04). 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 Uurik at the time of the atomic explosion
andtherefore not exposed to significant radiation,
was 2.21 £0.13, which is extremely close to the
mean value for the Rongelapese. Among the Utirik people 83% were high excretors, whichis not
significantly different from the Rongelap group
percentage. A numberof complete families are included in the Rongelap sample (i.e., father,
motherand at least one child); of these the highexcretor 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 lowexcretor offspring was illegitimate, as
determined by blood group data, but the otherremains as an unexplained exception to genetic
hypothesis.
Rubini et al.?* have recently demonstrated that
BAIB excretion can be a sensitive indicator of
radiation exposure. The mechanism involved is
probablythe same as that underlying the effect of
nitrogen mustard on BAIB excretion.**? Such
agents markedly increase DNA breakdown; the
thy mine thus released is effectively converted to
es
ae mr a er ee ee
ee |
BAIB in man **:** and excreted in urine, since no
appreciable tubular reabsorption of BAIB occurs.*4 It is unlikely that the high incidence of high
BAIB excretors found in Rongelap is dueto radiation. The identical average BAIB values in the exposed and unexposed groups preclude the possibility that the elevation ts due to the fallout ex-
posure in 1954, and it appears that radiation exposure(at the levels received at Rongelap) has no
long-term effect on BAIB excretion. The lack of
correlation with the Cs'*? and Zn* body burdens
rules against the elevation being dueto the present
retained internal radiation. The nearlyidentical
values in the Utirik group who received a very
small dose of radiation, and who have much lower
body burdensof radionuclides, 1s also consistent
with the thesis that a high incidence of the gene
underlying B-amino-tso-butyric aciduria Is responsible for the observed BAIB excretion rate.
The expression of the normalgenetic difference is
probably due to differential metabolism of BAIB
by high and lowexcretors.**
The level of BAIB excretion among the Marshallese is the highest vet reported for any populauon. Blood group* and other anthropological
data on these people suggest a Southeast Asiatic
origin; if this is true, a high BAITB level can be
predicted for the populations of that region.
Studies of some Asiatic populations have given