31
usually associated with a consistent eosinophilia,
andindeed a large group of individuals with high
eosinophil counts had stools negative for parasites.
However, the greater incidence of eosinophilia
among Marshallese with stools positive for T.
tnchiura indicates that infection with this helminth
maybe a contributingfactor, but this does not enurely explain the generally high incidence noted.
Possibly chronic infections, particularly fungus
infections of the skin, may be partly responsible.
Anotherpossibility is trichinosis infestation, which
has to be considered seriously in view ofthe large
numberof rats on the island and the presence of
swine (used to a small extent for meat) roaming
freely. On the next survey serological tests for
trichinosis antigen will be carried out.
An unexpected finding was that the level of
serum protein-boundiodine in these people was
significantly above the normal range. Butanolextractable iodines on 6 cases also showed values
at the upper limit of normal, but thyroxinebinding capacity determinations on 12 cases gave
data inadequateto define precisely whether the
slight elevations weresignificantly different from
normal. However,it could be calculated that the
level of thyroxine-binding protein was insufficient
to cause the elevation of serum thyroxine (presumably to maintain a normal level of free thyroxine)
noted in these people.
The study of genetically determined traits has
proved mostinteresting in helping to establish the
anthropological background of the Marshallese
people and the homogeneity of the population
understudy. Interesting findings in the studies of
blood groupings were the high frequency of the O
gene (78.9%), the extremely low frequency ofthe
M gene (14%), the highest incidence yet reported
of the R’ chromosome (98.5%), the presence of
10.8% of Duffy (Fy*) negatives, the absence of Kell
and Diegofactors, and a single sample of the A.B
group. These groupings most closely resemble
those of the people of Southeast Asia and Indonesia. Haptoglobin studies showed a very high
incidence of the | —1 type and the Hp’ gene exceeded only by that of the Yorubas of Nigeria. No
unusual hemoglobin types were noted. These
findings suggest a rather homogenous population.
RADIATION ECOLOGICAL STUDIES
It seems appropriate to discuss the Marshail
Island data as part of the world-wide fallout
problem. There has been much concern expressed
both in scientific journals and in populararticles
aboutthe hazard from fallout, particularly Sr°°.
The generalsituation as of mid-1957 has been
reviewed by Robertson and Cohn," with the conclusion that existinglevels of radiation from fallout
addlittle to the environmental radiation hazard.
Eisenbud and Harley®™present data indicating
that in the United States Sr®° continues (in 1958)
to be deposited at a rate of 11 to 54 mC/mi?. The
averagefor the rest of the Northern Hemisphere
is 16 mC/mi?, which is about twice the value for
the Southern Hemisphere. Kulp and Slakter*
concludethatthe diet of an average U‘S.citizen
in 1957 contained about 6.5 uuC Sr®°/g calcium,
which corresponds to an equilibrium base level of
1.6 upC/g if the discrimination factor between diet
and bone is 4. Finkel,®* in an appraisal ofthe
potential Sr®°° danger based on data from animal
experiments, concludes that the minimum effec-
tive dose in man maybe a burdenoffrom 5 to 10
uC Sr°*, in close agreement with an estimate of
6 to 15 uC based on the radium method of extra- —
polation. Hindmarshet aL.*’ have re-evaluated
the relative hazards of Sr®*° and Ra***. Their conclusion is that the currently accepted maximal
permissible dose figures for Sr*° are substanually
correct. Brues*reviews the arguments upon which
is based the fear that very low doses of Sr®° might
producea “very low (but in absolute numbers ap-
preciable) incidence of leukemia” and concludes
that the present datafail to indicate a linear relationship for dose and effect at low doses. He further emphasizes the fact that there are other
theories of the etiology of cancer, and thattheir
existence weakens the arguments of those who
would assign unrealistically high probabilities to
the role of single mutations as being the cause of
cancer.
Gilliam and Walter®* have studied the trends in
the mortality from leukemia. In most age groups
the death rate has been increasing exponentially
since 1921, with doubling times of about 15 to 20
years for most age groups. The younger age
groups, however, have recently shown a tendency
to level off, or, in the authors’ words, since 1940
there has been “a distinct tendency toward a decline in the rate of increase.”’ This tendencyis
more definite with decreasing age, and in the age
group 0 to | year there has been an actual decline
in the death rate from leukemia. If leukemia
follows from exposure to an environmental factor,