bution of plutonium in the body.
Urine
assays of plutonium workers, again
coupled with occasional autopsy results,
increased that knowledge.
The usual problem, however, is the in-
verse: urine data are available but the
amount of intake, and perhaps the time
of intake, is not known. In this case,
the current approach typically uses two
biokinetic components for plutonium
inhalation exposures: the first describes
how inhaled material enters the blood
system; the second relates the amount
in the blood to the amount excreted.
These two components translate urine
assays to a realistic estimate of the
amount of intake, and then the com-
plete biokinetic model is used to deter-
mine the distribution of that plutonium
throughout the body, which, in turn,
serves as the basis for calculation of ra-
diation dose to the individual.
The most uncertain step is this last
one—the calculation of a dose from a
known plutonium distribution. For ex-
ample, although it is well established
that much of the plutonium in the bone
is concentrated on the endosteal sur-
faces, there is still a great deal of con-
troversy about how to calculate the ac-
tual dose from this deposition. Pluto-
nium that is directly on top of the sur-
face will impart a much higher dose to
the osteocytes (bone cells) than plutoni-
um that is buried in the bone matrix,
even if only by a few hundred microm-
eters. The only evidence that actual
doses may be less than was originally
assumed is the fact that none of the
human plutonium patients and none of
the plutonium workers (with one possi-
ble exception) who lived many years
with plutonium in their bodies have ex-
hibited any evidence of plutonium-in-
duced tumors. This outcome is in high
contrast to radium, where many cases
of tumors were obviously present above
certain threshold levels.
What about the one possible exception?
In 1975, George Voelz, a medical doc-
tor in the Los Alamos Health Division
published a study of the Los Alamos
plutonium workers, which discussed the
fact that one of the radiation effects of
radium poisoning was the development
of osteogenic sarcoma, a rare bone can-
cer. He stated that “the age adjusted
death rate in the U.S. from all bone tu-
mors, including osteosarcoma, is only
about 1 per 100,000 persons per year.”
The appearance of 2 bone sarcomas in
15 cases of radium poisoning was evi-
dence that the sarcomas were, indeed, a
result of the radiation. In 1989, one of
the 26 Los Alamos workers, exposed to
plutonium in 1945 and 1946, had an os-
teogenic sarcoma. Bone sarcomas had
been observed in plutonium studies
with animals, including inhalation stud-
ies at plutonium levels comparable to
the maximum permissible lung dose for
workers. In a 1991 paper by Voelz and
Lawrence, it was stated that the “dose
estimate for our case . . . is similar to
the lowest range of doses for dogs that
have developed bone tumors when ex-
posed to Pu . . . but is much below the
dose for the lowest Ra-exposed person
with a bone tumor.” To insure a full
understanding of this one case, a new
dose calculation based on the two-term
power function is warranted.
However, this is the only possiblity to
date of a plutonium-induced cancer.
Most of the workers have lived longer
than average. It would seem important
to continue studying the plutonium
workers. Much could be learned for
little cost.
It is also important to remember that
occupational health protection for pluto-
nium was approached with the radium
tragedy in mind, which resulted in prac-
tices and standards being adopted that
made it much more unlikely that the
threshold for tumors would be reached
with plutonium. The almost total ab-
sence of such tumors indicates that the
practices established for plutonium
workers were, in the main, successful,
even though, from a statistical point of
view, the number of cases on which
conclusions can be based is too small to
be conclusive. But that in itself speaks
to the fact that the radium industry was
a situation in which the workers, early
on, were in an unregulated and un-
knowingly hazardous environment,
whereas even though the plutonium
workers, early on, were working under
hazardous conditions, they were never-
theless kept apprised of the dangers and
given whatever safety equipment be-
came available. As soon as it was fea-
sible, the work was moved into a high-
ly controlled environment in which the
safest procedures available were prac-
ticed and in which the equipment,
analysis techniques, and work proce-
dures were constantly upgraded as they
became available.
A great deal has been learned from the
human plutonium injection studies, but
much is left to be learned. However,
the early studies were valuable enough
to enable our country to perform its
weapons research and production at the
end of World War II and into the cold
war with confidence that the workers
doing the work were being protected
and that the estimates of their plutoni-
um doses would be accurate. The po-
tentially tragic consequences of work-
ing with a new and unknown substance
never came to be. For this, we are
greatly indebted to the radiologists con-
cerned with insuring safety during the
Mahattan Project and are even more in-
debted to the patients who were inject-
ed with plutonium (see “‘Ethical Harm’
and the Plutonium Injection Experi-
ments” on page 280).
s
Acknowledgements
Bill Moss would like to thank Darrell Fisher
for his encouragement and support, Gary Ti-
etjen for his work on the re-analysis of the
data as well as many helpful comments, and
George Voelz, Payne Harris, and especially
Julie Langham Grilley for their willing help
and valuable comments.
Further Reading
A collection of copies of the documents gathered
The Human Plutonium Injection Experiments
222
Los Alamos Science Number 23 1995