ATTACHMENT 3


April 12, 1944

TO: Mr. Joseph Kennedy
Mr. Kenneth Bainbridge

FROM: L. H. Hempelmann

SUBJECT: Effects of Toxic Agents

At the recent meeting of the health group in Chicago J. G. Hamilton 
reported on the results of his studies on the metabolism of plutonium. 
The following statements are based on experiments in which 15 micrograms 
of plutonium salt (chloride in the +3 valence state, nitrate in the +4 
and +6 states) was given to a series of rats by the usual three routes 
(orally, intra-pulmonarily, and intra-muscularly).

The studies indicated that plutonium in all three valence states is 
very poorly absorbed when taken by mouth,--less than .005%.

(1) When introduced into the lung and into the muscle, the +4 valence 
state was very poorly absorbed, resembling zirconium in this respect. 
In the case of the nitrate given intra-muscularly, only 12% was absorbed 
from the muscle in 16 days. When introduced into the lung, 93% was 
still present in this organ after four days.

(2) In the case of the +3 salt, 30% was absorbed from the muscle in 
16 days, and 55% was absorbed from the lungs.

(3) The +6 state was the most readily absorbed of all. 68% was absorbed 
from the muscle in 16 days, and 68% from the lungs.

In all these cases the organ which took up most of the absorbed 
plutonium was the bone, with more than half of the element going to 
the skeletal system in each case.

Conversation with the various members of the health groups from other 
projects indicated that very little is known about the metabolism and 
toxicity of polonium. In the literature, the only pertinent study was 
published in 1913. This indicated that the lethal dose of polonium for 
rabbits was 120 microcuries injected into a 3.9 kilogram rabbit. This 
amount will kill a rabbit within seven days and is comparable in effect 
to about 1,000 Roentgen units of x-rays. Using this figure, the lethal 
dose of polonium for a 50 kilogram man, on the basis of weight, would 
be about 1.5 millicuries. Because the tolerance of various species of 
animals differs, it seems probable that the actual lethal dose will 
probably be considerably less than this figure. Assuming the above 
figure to be correct, however, the tolerance dose would be .0001 of 
the above figure, or 1.5 microcuries.

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In view of the above information, it would seem wise to continue all 
the precautions which have been instituted in Building D. Even though 
little seems to be absorbed by mouth, the problems of ingestion and 
inhalation are so closely related that it would seem wise to me not to 
mention this fact to the men working with the material.

Discussion with the men concerned with health in other projects 
seemed to indicate that nose counts are the most reliable methods of 
determining whether or not people are being exposed to these toxic 
agents. Since any absorbed material will tend to go to bone, blood 
counts will give evidence of over-dosage,--but not until a relatively 
late stage. There are certain tests of organic components on the blood, 
such as nucleoprotein and lipoid phosphorus, which might give earlier 
evidence of local tissue damage, which might occur in the lung. It is 
hoped that we shall be able to undertake these tests on the people who 
are receiving the most exposure, as judged by the nose counts.

CC to Mr. Popham

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