DOE's worker health and mortality studies began in the early 1960s when the feasibility of using existing employee and facility records for conducting long-term follow-up studies was explored. Based on the promising findings from the feasibility study, a 5-year pilot study was initiated in 1964. The primary DOE sites selected for this pilot study were the Hanford Site in the State of Washington and the Oak Ridge Site, which consisted of three major facilities in the State of Tennessee. Other facilities operating at several smaller sites were also included. To obtain the information needed for a retrospective cohort study, considerable effort was expended on locating, copying, and abstracting data from various plant records located onsite and offsite. When it was determined that further processing and validation of these data would be necessary to ensure their proper use in epidemiologic studies, the Hanford cohort became the primary focus of the health and mortality studies.
In the 1970s, the study was expanded, and the responsibility for collecting and updating data for subsequent long-term worker studies was assigned to three epidemiologic research groups: Oak Ridge Associated Universities (ORAU), Los Alamos National Laboratory (LANL), and the Hanford Site, where staff from the Pacific Northwest Laboratory (PNL) and Hanford Environmental Health Foundation (HEHF) formed a team.
ORAU assumed responsibility for studies of worker populations at the Oak Ridge Site, which included the K-25 Facility (also known as the Gaseous Diffusion Plant), the Y-12 Facility, and the X-10 Facility (also known as the Oak Ridge National Laboratory or ORNL). In addition, ORAU was assigned the studies of workers at two gaseous diffusion plants in Paducah, Kentucky, and Portsmouth, Ohio; the Feed Materials Production Center in Fernald, Ohio; two uranium processing plants located at the Mallinckrodt Chemical Works in St. Louis and Weldon Springs, Missouri; and the nuclear fuel production plant, called the Savannah River Site (SRS), in South Carolina.
ORAU prepared a master roster of all contractor employees at each of these facilities and retrieved many of the death certificates used by the three epidemiologic research groups. Each research group then extracted and coded the cause-of-death information from the death certificates for use in their respective studies. Each worker was assigned a unique identifier number, which allowed information pertaining to that worker to be linked together, regardless of the research center that collected the data or the file in which it appeared.
The epidemiologic research group at LANL assumed responsibility for studies of all workers monitored for exposure to plutonium by contractors conducting operations at the following sites: the LANL/Zia Company in New Mexico; the Rocky Flats Plant in Colorado; the Mound Laboratory in Ohio; and the Pantex Plant in Texas. The LANL study population also included ORNL and SRS workers having potential exposures to plutonium. LANL also performed an additional, long-term clinical follow-up study of a small group of workers exposed to plutonium at Los Alamos during the early days of the Manhattan Project.
The epidemiologic research team in Richland, Washington, with staff at HEHF and PNL, took primary responsibility for studying the operations workers who were employed by the major contractors at the Hanford Site in Washington. This research team also performed several related studies. One of the larger studies was a combined mortality study that included workers at ORNL, Rocky Flats, and Hanford. The HEHF/PNL team, along with several researchers from the other centers, also participated in an international, combined mortality study, which was performed by the International Agency for Research on Cancer and included workers from these three sites. Smaller studies conducted by the Hanford team included congenital malformations that occurred in offspring of individuals who lived in communities near the Hanford Site and lung cancers among monitored Hanford workers.
During the performance of the various studies, efforts were made to determine the vital status of each worker included in cohort mortality studies at the selected sites. Mortality was ascertained from employee rosters through searches conducted by the Social Security Administration, the National Death Index, and other sources, as appropriate. Death certificates, requested from State vital records offices, provided cause-of-death information, which was coded according to the International Classification of Diseases. Personal radiation-monitoring information available at the sites was examined or collected for most studies.
Data were regularly collected by the three epidemiologic research centers. Each center used slightly different procedures and methodologies to merge, document, validate, and analyze the data. The work performed by the three epidemiologic research centers, as well as by a number of other researchers, during two decades resulted in the collection of valuable information on a large number of workers at DOE sites and in the publication of numerous scientific papers and articles.
The electronic data files generated in the course of worker studies are located in CEDR either as working data file sets or analytic data file sets.