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The Paducah Gaseous Diffusion Plant occupational cohort study: analysis of mortality patterns associated with grouped job titles.
Chan-C; Muldoon-S; Hughes-T; Aldrich-T; Tollerud-D
Research Louisville, October 20-24, 2008, Louisville, Kentucky. Louisville, KY: University of Louisville, 2008 Oct; :1657
The Paducah Gaseous Diffusion Plant (PGDP) is currently the only operating uranium enrichment facility in the U.S. It was commissioned in 1952 as part of a U.S. government program to produce enriched uranium to fuel military reactors and produce nuclear weapons. PGDP is the only DOE gaseous diffusion plant in the United States that has not undergone an assessment of worker mortality. Workers, government officials, and the surrounding community have raised concerns about potential health effects from current and past exposures at the plant. The DOE requested NIOSH to conduct an epidemiology study to address these concerns. This phase of the study focuses on mortality associated with particular job titles within the plant. Standardized Mortality Ratios (SMRs) using external referents from the U.S. adult population and Standardized Risk Ratios (SRRs) were calculated analyzing the cohort, stratified by race, gender, job exposure, and 5-year age and calendar years for 92 causes of death, including over 40 cancers. The Life Table Analysis System (LTAS) was used to analyze outcomes based on job title. Previous work had condensed all job titles at the plant into 44 grouped job titles based on similarity of task and exposures. Because many employees worked several jobs during their tenure at the plant, an analysis plan was devised that accounted for each grouped job title by setting up a binary variable indicating if the employee ever or never held a particular grouped job title. The plan was further refined by limiting analyses to grouped job titles that represented a minimum of 5% of the person years of the whole cohort. This narrowed the number of individual grouped job titles from 44 to 11. Examination of the raw data indicated that employees that worked Job 0004, Chemical Operator, also frequently moved to either Job 0002, Cascade, or Job 0016, Maintenance. Two additional categories were created in order to discriminate between differences in outcome based on these job titles. The additional categories were defined as: ever worked Job 0002 not Job 0004; and ever worked Job 0016 not Job 0004. Relative exposures for each grouped job title were estimated by building on the work of Hahn and Moser. Their studies assigned relative exposure levels for five metals and TCE exposure. Rankings of 0 to 5 were assigned based on long-term employee interview and plant records. Assigned levels frequently changed over time for a given exposure. An additive exposure level was calculated by adding the levels of the five metals and TCE. Where levels changed over time for a given exposure, the levels were averaged. The additive exposure level information was then used to condense the 17 maintenance job title categories into three variables: high, medium, and low exposure maintenance groups. Preliminary results indicate a strong healthy worker effect for all grouped job title categories, as well as the high, medium and low exposure maintenance groups and the restricted Cascade and Maintenance job titles. The range of SMRs for all causes of death was 0.55 to 0.92, achieving significance for all but two job categories. The lowest SMR was associated with the Job 0002 not Job 0004 category, and the highest with Job 0040, Security. SRRs for all causes of death ranged from 0.78 to 1.35, with no significance in any job category. Early examination of individual causes of death indicates significant elevations in SMRs for "other nervous system diseases" in Job 0004, Non-Hodgkin's lymphoma in Job 0040, and malignancies of the intestine for Job 0034.
Uranium-compounds; Exposure-levels; Exposure-limits; Nuclear-reactors; Workers; Mortality-rates; Morbidity-rates; Epidemiology; Statistical-analysis; Age-groups; Sociological-factors; Humans; Men; Women; Cancer; Metal-compounds; Metallic-compounds; Metallic-poisoning; Metallic-poisons; Author Keywords: occupational cohort; standardized mortality ratio; person years at risk
Research Louisville, October 20-24, 2008, Louisville, Kentucky
University of Louisville