The Human Plutonium
Injection Experiments
Number 23 1995 Los Alamos Science
183
Stafford Warren was educated at
the University of California at
Berkeley from 1918 to 1922 and re-
ceived his M.D. from the University
of California Medical School at San
Francisco in 1922. In 1925, he
was appointed as an assistant pro-
fessor of radiology at the University
of Rochester School of Medicine
and Dentistry, eventually serving
there as the Department of Radiol-
ogy Chairman. In April 1943, War-
ren was appointed a consultant to
the Manhattan Project to establish
the Rochester site. By November,
persuaded partly by management
at Eastman Kodak, who were run-
ning the uranium processing plant
at Oak Ridge, Warren was made
the medical director of the Manhat-
tan Project with headquarters at
Oak Ridge, Tennessee, and was
commissioned as a colonel in the
Army Medical Corps.
In the mid-thirties, Robert Stone, a
radiologist, and Joseph Hamilton,
an intern with a degree in chem-
istry, were recruited by Ernest
Lawrence from the University of
California Medical School in San
Francisco (at that time, part of the
UC, Berkeley system) to develop
biomedical applications for the
Berkeley cyclotron. One applica-
tion was the direct treatment of
cancer, and Stone pioneered the
use of cyclotron radiation for exper-
imental treatment of human cancer
patients. A second application was
to use the cyclotron to produce ra-
dionuclides for the internal ra-
diotreatment of disease. By the
late thirties, Hamilton and Stone
were involved with human metabol-
ic and clinical studies using sodi-
um-24, a short-lived radioisotope.
They hoped sodium-24 could re-
place the long-lived radium iso-
topes for the internal radiotreatment
of certain illnesses. Their studies
would involve using human volun-
teers—patients with leukemia, or
other illnesses, and normal healthy
subjects—to acquire comparative
data and to test for toxic responses
and evidence of cures. The
amounts of the radioisotope admin-
istered to the patients were always
well below what were considered
toxic levels relative to the then rec-
ognized risks from external expo-
sures to x rays and internal expo-
sures to radium (from the use of
soluble radium salts to treat a wide
range of illnesses).
Louis Hempelmann’s medical train-
ing was at Washington University in
St. Louis, followed by a residency
in Boston at the Peter Bent
Brigham Hospital. A fellowship
brought him to the Radiation Labo-
ratory at Berkeley in 1941, where
he studied radiobiology with Stone
and John Lawrence (Ernest
Lawrence’s brother) and worked on
the use of cyclotron-produced neu-
trons for therapeutic treatment of
cancer. At that time, Hamilton was
doing other research with a variety
of radioisotopes, including the cy-
clotron-produced fission product io-
dine-131. Many of those studies
used both normal human subjects
who had volunteered and patients
who were then tested for evidence
of responses that could lead to
medical treatments of illnesses, in-
cluding cures. In a 1942 article,
Hempelmann said that “if the cy-
clotron finds no place in medicine
other than to provide ‘tagged
atoms’ for medical studies, the
medical profession will owe Ernest
Lawrence an everlasting debt.”
s
A Radiotracer Experiment in the 1930s.
Joseph Hamilton (left) performs a tracer experiment in which the volunteer
drinks a solution containing radioactive sodium with his hand (out of sight)
inside a shielded counter that will detect the arrival of the radioisotope in
that part of his body.
The Medical Researchers
generated in reactors at Argonne (twen-
ty miles southwest of Chicago) and
later at Clinton, Tennessee, and that
material would be processed into metal
at the Chicago Met Lab before being
sent to Los Alamos. However, in May
1943, a committee appointed by Groves
reviewed the use of plutonium pro-
duced by cyclotrons and reactors and
decided it was necessary to locate the
final production steps for weapons ma-
terial at the same site that would assem-
ble the bombs. Thus, Los Alamos was
assigned the responsibility of the final
purification and production of the pluto-
nium metal, starting with the Clinton
product in 1944 and, later, with large
quantities of the Hanford product
(which was sent to Los Alamos in the
form of a plutonium-nitrate slurry).
The Met Lab would also continue its
innovative research for Los Alamos on
the physical and chemical properties of
plutonium using, in 1944, milligram
quantities of the Clinton product.
The new assignment resulted in an in-
crease in personnel in the Chemistry
and Metallurgy Division at Los Alamos
from about twenty in June 1943 to
about four hundred by 1945. It also
created an important difference in the
type of work at the two sites—the Met
Lab research was mainly “wet chem-
istry,” whereas the Los Alamos produc-
tion effort involved a considerable
amount of “dry chemistry,” resulting in
different types of health hazards, and in
particular, exposure to the airborne dust
of plutonium and its compounds.
In January 1944, at the same time the
first milligrams of reactor-produced
plutonium were being shipped from
Clinton, Seaborg and others at the Met
Lab began thinking seriously about the
fact that more and more people would
soon be working with gram quantities
of plutonium—perhaps thousands of
people at Hanford alone. Hamilton had
probably informed Seaborg of a 1943
paper by Robley Evans about the dan-
gers of radium and the deaths of radi-
um-dial painters in the 1920s, in this
way alerting Seaborg to a potentially
similar situation with plutonium. The
Evans paper estimated that as little as 1
or 2 micrograms of radium retained in
a person’s skeleton could cause cancer,
a latent radiation effect. It also ex-
plained the reasoning behind the occu-
pational tolerance limit of 0.1 micro-
grams for radium retained in the body
(see “Radium—the Benchmark for In-
ternal Alpha Emitters” on page 224 for
a fuller discussion of the radium toler-
ance levels).
Similarities with radium. That the
health risks for the intake and retention
of plutonium might be as dangerous as
those of radium was apparent from a
comparison of their chemical and nu-
clear properties. Both elements were
heavy metals that were expected to de-
posit in bone. Both had long half-
lives—1,600 years for radium-226 and
24,000 years for plutonium-239—and
both decayed by alpha emission. A
comparison of their specific activities (1
microcurie per microgram for radium-
226 and 0.06 microcuries per micro-
gram for plutonium-239) and the ener-
gies of their alpha particles, including
those of the daughters of radium, im-
plied that plutonium might be a factor
of 50 times less effective than radium
at causing physiological damage. But
because of the tragic deaths of the radi-
um-dial painters (dating from the use of
radium in 1917 to1918), it was impera-
tive to obtain metabolic data on pluto-
nium so that a safe tolerance limit
could be established for the Manhattan
Project workers.
On January 5, 1944, Seaborg sent a
memo to Stone, expressing his con-
cerns. He offered to help set up safety
measures for handling plutonium and
suggested that “a program to trace the
course of plutonium in the body be ini-
tiated as soon as possible.” Stone
replied by explaining Hamilton’s
planned tracer studies at Berkeley,
which would determine the metabolic
distribution of plutonium in animals,
and Hamilton’s need for milligram
amounts. Hamilton had apparently
been offered microgram quantities of
plutonium-239 prior to 1944, but he
had informed Stone that “the studies
can be much more accurate and much
more quickly done” when milligram
quantities were available (see “Detec-
tion of Internal Plutonium”). He pre-
ferred to wait until then to do the pluto-
nium metabolic studies, undoubtedly
fearing that experiments with smaller
amounts would lead to questionable re-
sults that would have to be repeated.
On January 15, Seaborg sent a second
memo to Stone.
I am seriously worried about the
health of the people in my section,
for which I am responsible, since
they will soon handle such relatively
large amounts of plutonium. I won-
der whether some plutonium should
be made available to Dr. Hamilton
for his distribution studies sooner
than the couple of months or more
indicated in your memorandum. . . .
The problem of health hazards as-
sumes even greater importance for
Site Y [Los Alamos] where so much
plutonium will be handled in so
large a variety of operations. It is,
of course, also important in connec-
tion with the operations which will
go on at Site W [Hanford], particu-
larly those involved in its final
isolation there.
In response to those concerns, manage-
ment at the Met Lab initiated discus-
sions about plutonium and its potential
for toxicity, beginning with a meeting
of the Project Council at the Clinton
Laboratory in Tennessee on January 19,
1944. Compton summarized the deliv-
ery schedule for plutonium from the
Clinton reactor as 0.5 grams that
month, 3 grams in February, and 3 to 4
grams in March and indicated that the
Plutonium Project was “still in the
lead” in the race with the uranium iso-
tope separation effort.
Tolerance limits. According to the
The Human Plutonium Injection Experiments
184
Los Alamos Science Number 23 1995
continued from page 182