180
Los Alamos Science Number 23 1995
physiological effects of ionizing radia-
tion was assembled under the direction
of Robert S. Stone. The intention was
to develop health-protection methods
for workers involved in the production,
purification, and fabrication of uranium
and plutonium, including development
of ways to monitor personnel for expo-
sures to ionizing radiation by blood
tests. In September, research was start-
ed to increase information about the
toxicity of uranium compounds.
The chemical toxicity of uranium (its
radiological risk was unknown) was
identified with heavy-metal poisoning
related to deposits in the kidney and
bone. Plutonium, on the other hand,
was an unknown health-risk factor. If
plutonium metal or compounds were in-
haled or ingested, where would they de-
posit in the body? What limits should
be set on internal body burdens that
would be safe? What tests would indi-
L E G E N D
Manhattan Project Sites Involved with
Human Plutonium Injection Experiments
Animal studies
Analysis of plutonium injection experiments
Injection of patients with plutonium
.
.
Los Alamos
(Site Y)
First atomic bomb
Joseph Hamilton
Director of Berkeley
animal and human
plutonium studies
Louis Hempelmann
Director of Los
Alamos Health
Group
Wright Langham
Biochemist who
analyzed Oak
Ridge and
Rochester pluto-
nium experiments
Berkeley
Discovery of plutonium
Birth of nuclear medicine
Hanford
(Site W )
Plutonium production
reactors
The Human Plutonium Injection Experiments
The Human Plutonium Injection Experiments
Number 23 1995 Los Alamos Science
181
cate when these body-tolerance limits
were being approached? As a result of
such concerns, efforts in health protec-
tion paralleled the growth of the nu-
clear weapons research (see “The Med-
ical Researchers”).
A contract was issued in October 1942
by the Met Lab to the University of
California Radiation Laboratory at
Berkeley to study the metabolism of
the radioactive materials that would re-
sult from the fission process in natural
uranium piles. These studies, directed
by Joseph G. Hamilton, would initially
be limited to the metabolism in rats of
small quantities of cyclotron-produced
fission products (their radioactivity
would “trace” their course through the
body). As larger quantities of the
transuranics became available from the
Clinton pilot reactor in 1944, the stud-
ies would focus on the assimilation,
distribution, retention, and excretion in
.
Chicago
(Met Lab)
Plutonium Project
First nuclear chain
reaction
.
Oak Ridge
(Site X)
Pilot reactor
for plutonium
production
Rochester
Rochester Medical
Project
Robert Stone
Director of Met Lab
Health Division
Stafford
W arren
Medical Director of
the Manhattan Project
The development of atomic weapons by the Manhattan Project was
carried out during World War II at a number of universities and secret
laboratory sites across the country. The icons represent facets of the
plutonium injection studies carried out at each site, including both ani-
mal studies (no background) and human studies (red circle in back-
ground).
rats of neptunium, americium, plutoni-
um, as well as larger amounts of fission
products.
When the Manhattan Project took over
direction of the weapon programs, it set
up its own Medical Office under the di-
rectorship of Stafford L. Warren, from
the University of Rochester, and this
office started medical, health physics,
and biological research sections at other
centers. In April 1943, the University
of Rochester Project was authorized
based on the extensive experience of
the medical school there in conducting
biological studies with cyclotron-pro-
duced radioisotopes. In contrast to the
Met Lab and Los Alamos, the
Rochester Project was not directly in-
volved with the design or production of
the atomic bombs. It was responsible
for studying the biological effects of
various radioactive materials, using
animals as the host. Part of that work
included determining the comparative
toxicity of radium, polonium, and
plutonium.
At this same time, it was agreed that
the Chicago effort would continue to be
responsible for the health programs it
already had underway, including the
recommendation of health safeguards
for other Manhattan Project sites such
as Los Alamos and the plants involved
with production of weapon materials.
The Met Lab’s Health Division contin-
ued its animal research, including the
radioactive tracer studies by Hamilton
at Berkeley and, by 1944, acute plutoni-
um toxicity studies at the Chicago site.
Each of the sites within the Manhattan
Project established their own group of
people to provide on-site health protec-
tion. The Los Alamos Health Group
was created in March 1943 under the
direction of Louis H. Hempelmann and
began to plan for the health protection
of workers at Los Alamos. Oppen-
heimer’s original intent was to rely on
other project sites for the development
of the health-protection methods. How-
ever, by the summer of 1944, Hempel-
mann and Oppenheimer found they
could not always get the health-protec-
tion information they felt was needed,
and the Laboratory extended its activi-
ties, gradually taking on a role compa-
rable to other sites for health-protection
research and development on the haz-
ards of plutonium.
The heads of the various health divi-
sions—Stafford Warren for the Manhat-
tan Project at Oak Ridge, Robert Stone
at Chicago, Joseph Hamilton in Califor-
nia, and Louis Hempelmann at Los
Alamos—were destined to play a major
role in the decision to obtain plutonium
metabolic data from humans (see “The
Medical Researchers”). All four were
medical doctors with strong back-
grounds in radiology, and in 1941,
three of them—Stone, Hamilton, and
Hempelmann—were working at the Ra-
diation Laboratory at Berkeley. They
were thus knowledgeable about radia-
tion and its biological effects, including
research that involved the administra-
tion of small quantities of radioactive
materials into humans for biomedical
purposes.
By 1942, Stone had gone to the Met
Lab in Chicago as head of the Health
Division, and Hempelmann had moved
back to Washington University in St.
Louis (where he had received his med-
ical training). There he was responsible
for programmatic uses of that universi-
ty’s cyclotron. By the summer of 1942,
both Hempelmann and Hamilton, the
latter responsible for operations at
Berkeley’s cyclotron, were caught up in
demands related to the war effort. One
of their main responsibilities became
the production of plutonium by bom-
barding hundreds of pounds of uranium
nitrate to produce microgram quantities
of plutonium-239. The irradiated urani-
um from St. Louis was sent to the Plu-
tonium Project’s laboratories in Chica-
go where Seaborg’s group was learning
how to chemically isolate the plutonium
from the uranium and the highly ra-
dioactive fission products. The urani-
um irradiated at Berkeley was
processed at the Radiation Laboratory
under the direction of Art Wahl and
Joseph Kennedy, and much of that ma-
terial eventually went to Los Alamos.
The Berkeley and St. Louis groups each
produced about a milligram (a thousand
micrograms) of plutonium-239 before
January 1944, when the first gram
amounts of reactor-produced plutonium
started becoming available from the
Clinton site.
The Los Alamos Health Group. Op-
penheimer, at the recommendation of
John Lawrence at Berkeley’s Radiation
Lab, asked Hempelmann to head up the
Health Group at Los Alamos in March
1943. Before coming to Los Alamos,
Hempelmann visited the Met Lab in
Chicago and discussed plans for the or-
ganization of the new Health Group. It
was the opinion of the Chicago people
that changes in blood counts, such as
increased numbers of white blood cells,
would be the most sensitive indicator of
significant radiation exposures. If he
was to be the “hematologist-in-chief” at
Los Alamos, Hempelmann wanted to
learn as much as he could about this
subject from Stone and others.
While in Chicago, Hempelmann also
met with John Manley, who was re-
sponsible for planning for the Los
Alamos Laboratory. Manley told him
that about fifty to sixty men might be
exposed to radiation hazards at Los
Alamos and he did not anticipate the
hazards being greater than those associ-
ated with supervoltage machines, such
as cyclotrons. At that time, the Chica-
go Met Lab was responsible for pluto-
nium research, and Los Alamos was re-
sponsible for weapon design. As a
result, Manley did not envision an ex-
tensive research effort at Los Alamos
using plutonium. It would not be long
before that would change.
Worries About the Health
Hazards of Plutonium
Originally, it was intended that mil-
ligram amounts of plutonium would be
The Human Plutonium Injection Experiments
182
Los Alamos Science Number 23 1995
continued on page 184