The Human Plutonium Injection Experiments

volved in other studies.  For example,

many of Hempelmann’s staff were

commandeered late in 1945 to study the

effects of the atomic bombings in

Japan, and on their return, many of

those were released from service.  By

1946, Langham was deeply involved in

studies of the fallout from atmospheric

testing of weapons in the Pacific.

Stone returned to Berkeley, and both

Bassett and Warren eventually went to

the University of California in Los An-

geles.  The attention of the researchers

was thus diverted away from the injec-

tion studies.  

In addition, the transfer, in January

1947, of the Manhattan Project to the

newly formed Atomic Energy Commis-

sion caused the injection studies to be

viewed in a different light—a senstive,

potentially embarrassing one.  As a re-

sult of these various forces, no one fol-

lowed up the ten remaining plutonium

injection patients, the only people with

well-characterized plutonium doses, to

determine the impact of plutonium on

their health.  Likewise, the eventual

long-term study of Los Alamos plutoni-

um workers with significant body bur-

dens was not started until 1952.  

The impact on workers. What was

the impact of the injection studies on

the people working with plutonium at

Los Alamos?  In July 1945, five Los

Alamos plutonium workers were judged

to have body burdens equal to or above

the 1-microgram tolerance limit (calcu-

lated by applying the 0.01-per-cent ex-

cretion model to their urine assays).

These workers were removed from fur-

ther work with plutonium.  When

World War II ended in August 1945,

all plutonium-related research at Los

Alamos was discontinued pending com-

pletion of a new plutonium laboratory

then under construction (see “Middle

Years—1952 to 1978 at DP Site,” page

134).  The new facility was fully occu-

pied by November 1945, and the im-

proved working conditions reduced the

probability of serious accidental expo-

sures.  After that, very few workers re-

ceived significant plutonium exposures,

especially those involving inhalation.

Meanwhile, the 0.01-per-cent excretion

model continued as a straightforward

way to estimate a worker’s accumulated

plutonium burden (firmly established by

a 1946 summary of the human injection

data by Russell and Nixon).  For exam-

ple, several editions of the General

Handbook for Radiation Monitoring

published by Los Alamos (LA-1835)

after the war stated that measuring 14

disintegrations per minute for plutoni-

um-239 in a 24-hour urine sample col-

lected about a month after exposure

would correspond approximately to a

permissible body burden.  That activity

was equivalent, for a 0.01-per-cent ex-

cretion rate, to a 1-microgram (or 63-

nanocurie) body burden.

Chronic exposures. The primary ex-

posure for workers in 1945 was not a

single acute dose, as it was for the pa-

tients injected with plutonium.  Rather,

the main concern was chronic inhala-

tion of low levels of plutonium dust,

followed by gradual absorption into the

body of a fraction of the plutonium that

had built up in the lung.  Determining

body burdens for this latter type of ex-

posure was more complicated because

the total excreted plutonium was actual-

ly a sum of excretions from many indi-

vidual exposures (or absorptions of ma-

terial from the lungs).  Using the

Langham power-function equation to

estimate an effective body burden was

highly sensitive to the selection of data

used to make the calculation.  As a re-

sult, it was important to determine if

the picture of plutonium distribution

and excretion based on the injection

studies of humans and animals was an

accurate one for plutonium workers.

On December 30, 1958, an accident oc-

curred in the plutonium processing fa-

cility at Los Alamos in which an expe-

rienced chemical operator, Cecil Kelley,

received a sudden burst of intense neu-

tron and gamma radiation.  It was later

estimated that Kelley received a total

dose to his body of 4000 to 5000 rad

(around 12,000 rem), a tremendous

amount of radiation, and he died about

35 hours later.

Kelley had been a plutonium worker

for two-and-a-half years from 1946 to

1949 and, again, for three-and-a-half

years from 1955 through 1958.  During

that time, especially the early years, he

had been exposed to plutonium dust on

a regular basis and had a record that in-

cluded 18 instances of high nose-swipe

counts and ten instances of minor expo-

sure, for example, during the cleanup of

a plutonium spill or from a slight skin

laceration.  Throughout that period, reg-

ular urine assays had been performed

that usually showed slight amounts of

plutonium.  Records were also available

on the average low-level concentrations

of airborne plutonium in the areas

where Kelley had worked.

Kelley’s tragic death, thus, became an

opportunity to compare an individual’s

extensive health and exposure records,

including urine assays, to a postmortem

analysis of tissue.  Autopsy samples

were taken from throughout Kelley’s

body so that plutonium concentrations

could be measured.  (The accident it-

self, an exposure to neutrons and

gamma rays, had no impact on the lev-

els or distribution of plutonium in his

body.)  It was found that about 50 per

cent of the plutonium was in the liver,

36 per cent in the skeleton, 10 per cent

in the lungs, and 3 per cent in the respi-

ratory lymph nodes.  Intravenous injec-

tion of plutonium in humans had shown

a somewhat different distribution: 65

per cent in the skeleton and 22 per cent

in the liver, for example.  The investi-

gators (Harry Foreman, Wright Lang-

ham, and Bill Moss) felt that such dif-

ferences might have been a result of

differences in the chemical and physical

nature of the plutonium (a soluble salt

versus dust particles).  Finally, the total

plutonium in Kelley’s body was esti-

mated to be 18 nanocuries (equivalent

to 0.29 micrograms of plutonium-239).

The Human Plutonium Injection Experiments

Number 23  1995  Los Alamos Science  

continued on page 216

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