The Human Plutonium Injection Experiments

The Human Plutonium Injection Experiments

194

Los Alamos Science Number 23  1995

nary and fecal excretion rates—factors

of 1 to 5 in rodents and 1 to 2 in

dogs—cast doubt on whether or not the

use of an 0.01-per-cent daily urinary

excretion rate for humans was even ap-

propriate.  Animal data showed that

more plutonium was usually excreted in

stools than in urine.  Would stool as-

says be more sensitive than urine as-

says for humans?  The only way to ad-

dress these concerns was with further

studies.  But time was critical.  Many

of the people at Los Alamos were

working seven days a week to meet a

schedule for the first test of a plutonium

weapon in July 1945.  There was no

time to start another series of animal

experiments, and thus, the researchers

turned to human studies.

A fact important to the planning of the

human injection experiments had been

established in experiments with rats at

Los Alamos.  Five groups of rats had

been injected with plutonium doses that

ranged from 0.032 to 52 micrograms,

and the excretion rate over a 5-day pe-

riod was determined for each group.

Wright Langham, a biochemist and the

Biochemical Section Leader under

Hempelmann, reported in May 1945

that “the per cent of the total injected

dose excreted in the urine . . . is inde-

pendent of the size of the dose adminis-

tered.”  This meant two things: first, a

single injection dose, rather than a se-

ries of different doses, would be ade-

quate for the study; and second, at a

given time after the injection, the

amount of plutonium being excreted

was simply proportional to the amount

injected, and the excretion rate could be

used as a direct measure of the pluton-

im retained in the body.  The problem,

of course, was establishing accurately

the specific ratio for humans.

Hamilton’s original work with rats in

1944 had not developed complete ex-

cretion curves, but rather pooled sam-

ples for chemical analysis at broadly

separated intervals (days 4, 16, 32, and

64).  On the other hand, Langham’s

studies with rats had used a daily sam-

pling basis out to 44 days after the in-

jections.  Those data, available in July

1945, would have convinced Langham

that excretion could be accurately

“modeled” using linear plots with the

data collected daily for only a few

weeks, apparently a key factor in the

planning of the human experiments.  

Working with the Medical Corps.

On March 26, 1945, Hempelmann and

others at Los Alamos met with Lt.

Colonel Hymer Friedell from the Man-

hattan Project Medical Section under

Warren.  In a memo summarizing the

meeting for Oppenheimer, Hempelmann

stated that they had requested the Man-

hattan Project Medical Corps “to help

make arrangements for a human tracer

experiment to determine the percentage

of plutonium excreted daily in the urine

and feces.”  They further suggested that

“a hospital patient at either Rochester

or Chicago be chosen for injection of

from one to ten micrograms of material

and that the excreta be sent to this labo-

ratory [Los Alamos] for analysis.”

The memo also discussed other topics

related to the hazards of plutonium, in-

cluding improvement of protection

methods, study of ways to treat overex-

posed personnel, and development of

methods to detect plutonium in the

lungs.  One of the requests summarized

in the memo was “a more satisfactory

relationship of this project [Los Alam-

os] with the Medical Program of the

Manhattan District so that the facilities

of the Manhattan District will be avail-

able for the solution of our problems,”

and it was suggested “that channels be

established through which our problems

can be brought to the attention of those

individuals who plan the research pro-

gram of the Manhattan District.”

Oppenheimer followed up these discus-

sion with a letter to Warren in which he

said:  

We all have the feeling that at the

present time the hazards of work-

ers at Site Y are probably very

much more serious than those at

any other branch of the Project,

and that it would be appropriate

that the medical program of the

Manhattan District consider some

of our problems rather more inten-

sively than they have in the past. 

. . . Although we would have some

ideas of how to pursue all of the

topics mentioned, we have, as you

know, neither the personnel nor the

facilities which would be involved

in this. . . . It was our impression

that if other workers on the med-

ical program were better informed

about what was important from our

point of view they would probably

be glad to help us out.

He was reiterating the same point he

had made the year before.

The people at Los Alamos were thus

ready to move to the third part of the

plan that been had agreed upon in Au-

gust 1944.  Warren was also ready.  In

a December 2, 1944, memo (outlining

points for a meeting two days later), he

had stated that there was an urgent need

both for experiments to establish “the

ratios of blood level to urine and fecal

excretion following a single intravenous

injection of radium and product in rats”

and for “[similar] tracer experiments on

humans . . . so that the comparison

(factor) can be made between the rat

data and human data.”  The three peo-

ple he identified in conjunction with

this work were “Dr. [William] Bale [at

Rochester], Dr. Hempelmann, and Dr.

[Kenneth] Cole [at Chicago].”

It is easy to get the impression that the

human plutonium injections were isolat-

ed experiments.  However, a number of

other studies had been or were being

conducted.  For example, in 1941,

Hamilton’s team injected six patients

who had bone cancer with radioactive

strontium.  That metal is also a bone

seeker, and Hamilton was studying it as

a possible therapeutic agent for the

treatment of bone cancer. 

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