The Human Plutonium Injection Experiments

all feces and urine are to be collected

according to a precise sampling sched-

ule and periodic blood samples are to

be taken.  These are to be carefully as-

sayed for ‘product’ by the Santa Fe

group [Los Alamos].”  In other words,

blood, urine, and fecal samples taken

both during the control period and after

the injections would be sent to Los

Alamos for determination of plutonium

content (or normal radioactivity).

The stated purpose of the experiment

was “to establish on a statistical num-

ber of subjects the relationships existing

among such factors as the amount of

product in the body, the level of prod-

uct in the blood, the amount excreted in

the urine, the amount excreted in the

feces, and the variations of the above

with time.”  Such data would provide

“a statistical basis for diagnosing body

internal contamination from the analysis

of urine or feces, the obvious purpose

of which is to retire workers before

they have received harmful amounts of

the material.”  Data would be collected

for 25 days, a time limit that focused

the study on the early excretion rate

when it was at its highest level.  The

early rate, of course, was important to

the immediate evaluation of workers

who had experienced accidental expo-

sures to plutonium.

Selection of patients. The plan left the

selection of subjects “entirely up to the

Rochester group.”  However, the partic-

ipants at the Rochester meeting “more

or less agreed that the subjects might be

The Human Plutonium Injection Experiments

202

Los Alamos Science Number 23  1995

Louis Hempelmann became interested in the use of the cyclotron in medicine and

biology in 1941, and this interest set the stage for an illustrious career in the med-

ical field of radiology, health physics, and epidemiology.  His work ranged from the

study of radiation effects among plutonium workers at Los Alamos to a monumental

follow-up study of thyroid cancer among infants given radiotherapy.

Born in St. Louis on March 5, 1914, Hempelmann followed his father, an internist,

into medicine.  His undergraduate and medical degrees were earned from Wash-

ington University in St. Louis, where he also completed an internship in pathology.

In 1941, Hempelmann spent four months as a Commonwealth Fellow with John

Lawrence at the Radiation Laboratory in Berkeley, honing skills in the use of the

cyclotron for radiotherapy.

Shortly after the war broke out, J. Robert Oppenheimer, Director of the Laboratory

at Los Alamos, petitioned John Lawrence for candidates to oversee the health as-

pects of employees at Los Alamos.  Oppenheimer envisioned an urgent need for

safety measures for the radiation work being done and had even specified blood

tests be taken before there were “any extra neutrons on the Hill.”  Lawrence sug-

gested Hempelmann, who arrived at Los Alamos in March of 1943, and assumed

responsibility for the safety of all technical operations and for directing the Health

Group.  After the war, Stafford Warren wrote a memo to the Director of the Los

Alamos Laboratory, Norris Bradbury, in which he praised Hempelmann:

He has done an exceedingly good job.  Many men owe their lives to Dr.

Hempelmann’s sound judgment and the practices which he instituted in a new

endeavor.  There are no men trained in the field nor even in industrial medi-

cine by which to replace him if he is permitted to resign.

While at Los Alamos, Hempelmann started the work for which he was best known:

he looked for radiation effects among twenty-seven workers at Los Alamos who

had received exposures of plutonium and followed them throughout his career.

George Voelz, his collaborator, continues this study.

In 1949, Hempelmann published a paper on the danger of using fluoroscopes to fit

children’s shoes.  Shoe-fitting fluoroscopes soon disappeared.  In 1950, Hempel-

mann joined the faculty at the University of Rochester as an Associate Professor of

Louis Hempelmann (right) with George

Voelz looking on.

Louis H. Hempelmann—1914-1993

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chronic arthritics or carcinoma patients

without primary involvement of bone,

liver, blood or kidneys.”  It was impor-

tant that “the subjects have relatively

normal kidney and liver function, as it

is desirable to obtain a metabolic pic-

ture comparable to that of an active

worker.”  

Thought was given to the types of clini-

cal testing that should precede and fol-

low the plutonium injection.  For exam-

ple, hematological tests were needed to

see if radiation damage from the pluto-

nium would be obvious in the blood.

Other tests might detect changes in

bone, liver, and kidney function.  Such

clinical testing was the responsibility of

the Rochester group.

The patients would each “receive a sin-

gle intravenous injection of ‘product’”

containing 5 micrograms of plutonium.

The stock solutions were to be prepared

by Langham at Los Alamos as plutoni-

um nitrate (in the +4 oxidation state),

and one of the Rochester doctors would

use aliquots of this stock solution to

prepare injection solutions of the pluto-

nium complexed with citrate.  Before

each injection, an assay would be per-

formed with an alpha counter to make

sure that there were approximately 5

micrograms of plutonium in every half

milliliter of solution.

It was also stated in the plan that:

Col. Warren proposed Lt. Valen-

tine as the one to do the injections.

Number 23  1995  Los Alamos Science  

203

Experimental Radiology and served as Chairman of the Department of Radiology

from 1960 through 1971.  During this period, Benedict Duffy published a paper on

a case-series of twenty-eight children who had developed thyroid cancer.  Surpris-

ingly, ten of the children had received thymic radiotherapy as infants.  Soon after,

Hempelmann began his now-famous study of infants who had been given radio-

therapy for thymic enlargement.  Follow-up surveys of these children, conducted

throughout his career, found an advancing excess of thyroid cancers, excessive

benign tumors, and possible immunological abnormalities.  Such research required

abilities in scientific design and the organization of large amounts of data because

the work was initiated before standard chronic-disease epidemiology techniques

had emerged.  The finished study is considered a masterpiece by health physi-

cists, and today, is being continued by Roy E. Shore of New York University.

In 1967, Hempelmann suggested to Fred Mettler, a student who wanted to study

radiation effects in humans, that he conduct a study of women who had received

x-ray treatments for acute postpartum mastitis 10 to 25 years earlier.  They found

that among 606 women, there were 13 cases of breast cancer when only about 6

were expected.  A number of important studies followed.

At Rochester, Hempelmann and his colleague’s research interests included identi-

fying blood and urine that could serve as markers to determine the degree of tis-

sue damage from exposure to ionizing radiation and to clarify the mechanisms in-

volved in the production of radiation-induced creatinuria in animals.  In the 1950s

and 1960s, Hempelmann’s laboratory did studies of cellular destruction and protein

breakdown induced by exposure to x rays, the effect of ionizing radiation on the

deoxyribonuclease activities of body fluids, the effect of x-ray exposure on the de-

oxyribonuclease activity of lymphoid tissue, and the effect of x rays on nucleic acid

catabolism and collagen metabolism.  Many significant publications on the effects

of ionizing radiation on animals were written by Hempelmann and Kurt Altman 

during this time.

Hempelmann authored or co-authored numerous scientific papers throughout his

career.  The last report, which appeared in 1986, updated his three career-long in-

terests: the plutonium workers, thyroid cancer after thymic irradiation, and breast

cancer after postpartum mastitis.  The work of this remarkable man remains as

significant today as it was critical in the past. 

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The Human Plutonium Injection Experiments

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