Scientific Efforts

Early Scientific Studies

Several early USTR studies were initiated. These included a comparison between systemic plutonium depositions found in the first 30 autopsy cases and estimates made from urinalysis during the worker’s life. This study was vital to operational health physics programs in that it assessed the adequacy of biokinetic models used for operational assessment of plutonium depositions. The causes of death in the first 30 cases were examined, and it was concluded that “…the usual causes of death were encountered.” Also the greatest concentrations of plutonium were found in the tracheobronchial lymph nodes, lungs and liver. Researchers quickly realized that a major aspect of their work would be the study of the distribution of plutonium in the various tissues, and that whole body analyses would be needed to avoid errors associated with the limited size of tissue samples obtained at autopsy.

In 1975 a controversy erupted regarding the published results of the first 30 autopsies performed by the Registry, which were detailed in a paper in the open peer reviewed scientific literature (Norwood and Newton 1975). The causes of death of these cases were evaluated by Sidney Wolfe of the Ralph Nader Health Research Group, who concluded in an article in the September 1976 Bulletin of the Atomic Scientists that the cancer death rate among plutonium workers was twice the cancer death rate for white males generally. This conclusion was refuted by Director Norwood and others who noted that the Registry population was a biased one, and as such was not amenable to such analysis.

Epidemiologic Studies

A second major aspect of the USTR’s work involved developing an epidemiologic study. By 1974, a preliminary study design had been developed for the Registry. Broader studies of the Hanford and Los Alamos workforces were being carried out at the same time.  These studies were sponsored independently from the Registry by the AEC and its successors. The Registry director Norwood was the principal author on one of these studies, which was presented in a 1975 a workshop on the bioeffects of plutonium and radium. This study, which focused on the health of Hanford plutonium workers, and the Registry’s role with respect to epidemiologic investigation were important discussion topics at a USTR Workshop held in Denver on February 27, 1975. A carefully constructed epidemiologic study was planned, which would likely be carried out semi-autonomously by LANL under the coordination of the Registry.

The advisory committee observed at its June 1977 meeting that both the USTR and LANL appeared to have overlapping and perhaps conflicting responsibilities with respect to the conduct of epidemiologic studies of transuranium element workers. The Committee recommended that Drs. Breitenstein and Voelz pursue resolution of the epidemiologic study matter and report their findings and conclusions back to the Committee. Breitenstein and Voelz met with Walter W. Weyzen to discuss the relationships and responsibilities of the USTR and LANL, concluding that it was best to leave the matter unresolved pending better definition of the overall Department of Energy Occupational Worker Epidemiology Study. Within a matter of months, however, the USTR was out of the epidemiology research area. Its next Annual Report of the Registry reflected a major change in direction: greater emphasis was placed on biokinetics and health physics, and epidemiologic study was no longer a stated purpose of the Registry. In fact the Annual Report made no mention of epidemiology.

An Increase in Publications

When Kathren began working half-time as scientific support, he devoted his effort largely to analysis of the data accumulated by the Registries with an eye towards publication of papers in the peer reviewed scientific literature. He encouraged publication of Registries sponsored work and worked behind the scenes to expedite publication of the apparently stalled case report on USTUR 102, the first whole body donor. These efforts led to a burgeoning number of publications by Registries staff and collaborators in peer reviewed scientific journals; the record shows only 13 publications by Registries staff or based on Registries data in the peer reviewed literature prior to 1984, and 47 publications during the period 1984-92, plus a number of miscellaneous and ancillary publications. These included not only the five Case 102 papers previously mentioned, but also publications relating to the distribution of actinide in the skeleton, partitioning of plutonium and americium between liver and skeleton, comparison of whole body depositions determined at autopsy with those made during life, and an evaluation of various biokinetic models for plutonium based on postmortem findings in several whole body donations.

Validating Mathematical Models

Employers generally evaluate their radiation protection practices by monitoring workers for intakes. Since actinides continue to be excreted from the body long after intake, bioassays are a common monitoring technique. The daily urinary excretion of these metals is measured and a mathematical model is used to estimate the total body content. Since these models were historically based on animal studies and a very limited number of human cases, the USTUR autopsy data provides a valuable tool for validating them. Estimated organ burdens can be compared to the actual organ burdens, and the mathematical models can be altered to reflect observed differences.

Several studies have explored the differences between actual body burdens and the body burdens calculated from then current mathematical models. In one study, the plutonium urinalyses results from 17 cases were sent to six different radiation protection groups. These groups were asked to estimate plutonium body burdens based upon the urine contents. Their estimates were 4 to 8 times higher than the body burdens measured by radiochemical analysis. Another study used the, then current, mathematical models for plutonium in the body to estimate the plutonium body burden, skeletal contents and liver contents. Estimations of the body burdens based on urinalysis data were very close; however the estimated skeletal content was two times the measured content and the estimated liver content was one-half the measured content. Based upon studies such as these, the mathematical equations used to describe distributions of plutonium in the body have been revised.

Contributions to NCRP and ICRP Publications

Most radiation protection standards regarding actinide elements originate with the National Council on Radiation Protection and Measurements (NCRP) and the International Commission on Radiological Protection (ICRP). Committees of distinguished scientists examine all available biokinetic data and publish recommendations about methods for calculating radiation doses to organs. Health risks and effects are also examined and used to recommend dose limits that will avoid adverse health effects. These recommendations are the basis for the radiation protection regulations established by governmental agencies such as the U. S. Nuclear Regulatory Commission and the U. S. Department of Energy and their equivalents in other nations.

USTUR data has been incorporated into several NCRP and ICRP recommendations which address the biokinetics of uranium, plutonium, and americium in the human body. USTUR data were used in ICRP Publications 56, 66, and 67. These documents model the biokinetics of elements in the lungs and other body organs. USTUR data also made an important contribution to ICRP Publication 70, which dealt with the distribution of material in the skeleton. The USTUR had analyzed several skeletons from whole body donations for uranium, plutonium, and americium. Individual bones were analyzed separately such that scientists could determine which bones and bone types contained the greatest depositions of the actinide elements. This allowed them to calculate which parts of the skeleton receive the greatest radiation dose from uranium, plutonium, and americium.