The Human Plutonium Injection Experiments
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The Human Plutonium Injection Experiments William Moss and Roger Eckhardt T he human plutonium injection experiments carried out during and after the Manhattan Project have received tremendous noto- riety in the past year or so owing to the Pulitzer-prize winning journalism of Eileen Welsome in the Albuquerque Tribune in 1993. The purpose of those experiments was to develop a diagnostic tool that could determine the uptake of plutonium in the body from the amount excreted in the urine and feces. This tool was essential for the protec- tion of workers who would produce and fashion plutonium metal for use in the early atomic bombs. The idea was to remove a worker from the job if and when it was determined that the he had received an inter- nal dose that was close to or over the limit considered safe. Although some of the results of the studies were declassified and re- ported in the scientific literature in the early fifties (and further reports appeared in the seventies), the names of the subjects were not dis- closed. Investigative reporting by Welsome uncovered the identities of five of the eighteen subjects and gave details about the circumstances and lives of three of them. The secret nature of the studies and the fact that the subjects may not have been informed about what was being done to them has generated outrage and distrust in the general pubic regarding the practices of the national laboratories. Why were such experiments done? Who allowed them to happen? The Secre- tary of Energy, Hazel O’Leary, equally disturbed, pledged an era of openness in the Department, promising to make available to the public all information that could be located that was pertinent to those and
Louis Hempelmann similar radiation experi- ments with humans. This article is intended to tell the Los Alamos story of these experiments and their aftermath. The article is based on memos and other documents that were collected by one of the authors (Moss) and were released to the public as a result of Secretary O’Leary’s openness initiative. Los Alamos was not directly in- volved in choosing the subjects for the experiments nor in carry- ing out the clinical studies. Nev- ertheless, the motivation for the experiments arose at Los Alamos and scientists at Los Alamos were involved in planning the experi- mental protocols, preparing the ma- terial to be injected in the subjects, and analyzing the results. They were involved both at the time the experiments took place and years later when it became clear that re- analysis was appropriate. Our intent in reviewing this story is to give enough scientific and quantitative details to bring out two areas that are usually not adequately addressed in the press and other popular reports. The first area is the purpose of the studies. What was to be learned, and how well did the experiments succeed in accom- plishing the stated goals? The second area is the significance of the results for the protection of plutonium workers. How have those results aided our cur- rent understanding of the uptake, distri- bution, and retention of plutonium, and how have the results helped us to mini- mize the risks of internal exposure from plutonium? We will, in fact, show a new analysis of the data from the 1940s that, coupled with a recent human plu- tonium injection study using plutonium- 237, strengthens our understanding of the manner in which plutonium, once it has reached the bloodstream, distributes itself in the body. But first, we examine motivations and try to reconstruct why things were done as they were. For that we need to go back to the atmosphere of World War
II and the enormous pressures attendant on using unknown and uncharacterized materials to build the first atomic weapons. The Manhattan Project and Its Need for Plutonium In planning the development of the atomic bomb, scientists considered using two fissionable materials capable of sustaining a chain reaction—urani- um-235 and plutonium-239. Each pre- sented a different set of production and health-related problems. Uranium-235 was present in natural uranium in small amounts (0.7 per cent). Scientists faced the daunting task of separating kilogram amounts of uranium-235 from the much more plen- tiful uranium-238 isotope by taking ad- vantage of the slight difference in the mass of the two isotopes. For example, in the gaseous-diffusion method, gaseous compounds of the two isotopes diffuse through porous barriers or membranes at rates that differ by about 6 parts per thousand. Similarly, the elec- tromagnetic method passes a beam of ionized uranium through a magnetic field, and the two isotopes follow circu- lar paths that very gradually diverge.
In 1942, it was problematic whether enough uranium- such painstaking techniques to achieve the goal of hav- ing an atomic bomb by January 1945. It was deemed necessary to pur- sue plutonium-239 as an- other possible weapon ma- terial. Because plutonium is chemically different from uranium, it was thought that it could be produced in reactors through neutron absorption and then separated easily from its ura- nium parent and fission products by chemical means. Scientists had created tiny amounts of plutonium with the cyclotron at the University of California Radiation Lab- oratory in 1941 and demonstrated its favorable nuclear properties (see “The Making of Plutonium-239”). The phys- ical properties and the chemistry of plu- tonium were determined using only mi- crogram (micro = 10 -6 ) quantities. Such small amounts and the fact that plutonium emits alpha radiation, which doesn’t penetrate the skin, meant the risk of handling plutonium, compared to gamma-emitting radionuclides, was not a major concern. In fact, the alpha activity of these small quantities was the only means to track and account for the material. The discovery of plutonium led the Of- fice of Scientific Research and Devel- opment to inaugurate work on plutoni- um for a weapon design. The work The Human Plutonium Injection Experiments 178
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