The Human Plutonium Injection Experiments

the most frequent order of descending

plutonium concentrations, were respira-

tory lymph nodes, lungs, liver, and

bone.  In the two cases where urine as-

says definitely indicated a significant

positive exposure and analyses of both

lymph nodes and bone were possible,

the lymph nodes had plutonium concen-

trations 50 times higher per gram of tis-

sue than the bone.  Thus, inhalation ex-

posures resulted in the entry of

plutonium into the respiratory lymph

nodes, a phenomenon that should obvi-

ously not have been seen (and was not

seen) in the injection studies.  (For a

summary of what has been learned

from autopsy studies, see “A True Mea-

sure of Exposure—the Human Tissue

Analysis Program at Los Alamos.”)

Additional Data from the

Plutonium Patients

In 1969, Patricia Durbin, a biophysicist

at the University of California, Berke-

ley, was involved with metabolic work

on various radioisotopes, including

americium, that led her to the published

work on plutonium.  Wanting to learn

more, she began investigating the

records and data on the plutonium

human injections and trying to locate

further information about the patients.

In a letter, dated April 23, 1969, to Dr.

John Howard, an administrator at the

University of California Medical Center

in San Francisco, she said:

Most of the patients injected with

Pu were studied at other hospitals

around the country, and although

most were elderly and expected to

have short life expectancies at the

time of injection, some were misdi-

agnosed.  Because of this, there

was an understandably great up-

roar when the civilian A.E.C. took

over from the Manhattan Engineer

District.  As a result, the human

data thus obtained was classified

“Secret”, and so it remained for

some years.  All efforts to follow

up on those persons who had been

The Human Plutonium Injection Experiments

Number 23  1995  Los Alamos Science  

217

One of the problems in applying the Langham power-function model to urine

assays for plutonium workers was how to work backwards from the data to an

estimate of the body burden.  Urinary excretion data were usually low-level

values with considerable scatter.  Was a jump in a person’s excretion rate due

to analytical variations, physiological changes, or the result of a recent expo-

sure?  A method was needed that eliminated suspect data and then weighted

all the remaining data in the determination of the effective dose, or body bur-

den, and the effective exposure time for the Langham power-function.

In 1960, James N. P. Lawrence at Los Alamos devised a computer program

(called PUQFUA), based on the plutonium excretion power functions, that at-

tempted to account for multiple or continuous exposures occurring over a peri-

od of time.  Basically, the work period was split into intervals between urine

samplings and each interval was treated as a separate exposure incident.

Using the Langham power function, the dose for that interval was calculated

from the observed increase of plutonium in the urine over what was expected

from previous exposures.  If there was no increase, the exposure for that in-

terval was set to zero, and if there was a decrease from what was expected,

the previous data point was rejected, which helped eliminate contaminated

samples (later versions of the code rejected data more than 2 standard devia-

tions from the expected value).  The total excretion at any given moment was

then effectively the sum of many Langham power functions, one for each in-

terval, each on its own time scale.  The retained plutonium at any given time

was the sum of all the original exposures corrected for excretion losses.

One advantage of the PUQFUA method was that essentially all the urine data

were used to calculate a body burden rather than, as previously, using either

a single urine assay or an average over a time interval.  Individual assay

points could fluctuate greatly (because of analytical variations, contamination,

or physiological changes).  Lawrence’s approach weighted all but the rejected

assays equally and, thus, was more likely to arrive at a reasonable estimate.  

It should be emphasized that this approach, or any approach based on the ex-

cretion equations, was pertinent only for plutonium that had entered the blood

stream and could be excreted by the kidneys.  The program could, thus, cal-

culate an effective measure of internalized plutonium, but the result did not

give any indication of how much plutonium might be trapped in the lungs.

Only when such plutonium had worked its way into the blood stream would a

fraction of it appear as excreted plutonium.

Calculations with PUQFUA indicated that the body burdens of twenty-six Los

Alamos plutonium workers (occupationally exposed at Los Alamos between

1944 and 1946 and in the UPPU study of Langham, Hempelmann, and Voelz)

were 60 per cent higher than Langham had estimated with his approach,

which suggested that Langham’s power-function method underestimated pluto-

nium retained in the body.  However, we now know that the overestimate is

due to long-term urinary excretion that is truly higher than what is predicted by

the Langham model.  When a modified version of the PUQFUA code is used

that properly accounts for long-term data (10,000 days), the predicted body

burdens are consistent with the values obtained from tissue analysis studies.

A Computer Analysis of Plutonium Excretion

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