A Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard
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Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard A Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Institute for Occupational Safety and Health i Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard A Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard October 2004 i Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard Disclaimer Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health (NIOSH). In addition, citations to Web sites do not constitute NIOSH endorsement of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not responsible for the content of these Web sites. Ordering Information To receive documents or other information about occupational safety and health topics, contact NIOSH at NIOSH—Publications Dissemination 4676 Columbia Parkway Cincinnati, Ohio 45226–1998 Telephone: 1–800–35–NIOSH (1–800–356–4675) Fax: 513–533–8573 E-mail: [email protected] or visit the NIOSH Web site at www.cdc.gov/niosh HHS (NIOSH) Publication No. 2005-104 ii Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard Preface Ionizing radiation and its sources are used every day in medical, industrial and governmental facilities around the world. Although some health risks from ionizing radiation exposures are widely recognized, the association of these exposures to specific diseases, especially various types of cancer, remains uncertain. Workers at U.S. Department of Energy (DOE) facilities have produced nuclear weapons, provided nuclear fuel materials for power reactors, and conducted a wide spectrum of research related to nuclear safety and other scientific issues. While completing this work, many of the employees have been exposed to ionizing radiation and other potentially hazardous materials. Since 1991, the National Institute for Occupational Safety and Health (NIOSH) has conducted analytical epidemiologic studies of workers at DOE nuclear facilities, through a Memorandum of Understanding between the DOE and the U.S. Department of Health and Human Services (DHHS). The agreement occurred in response to recommendations to the Secretary of Energy in 1989 by the independent Secretarial Panel for the Evaluation of Epidemiologic Research Activities (SPEERA). This technical report, entitled A Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard, is one several products of the NIOSH Occupational Energy Research Program that are being published as a series. Most of these studies include detailed historical exposure assessments for radiation and other potentially hazardous agents so the health risks at different levels of exposure can be accurately estimated. Each of these studies contributes to the knowledge required to ensure that workers are adequately protected from chronic disease over their working lifetimes. Distribution of this final report addresses the recommendation of the SPEERA panel to make reports of study results more readily available to workers and the interested public. Additional information about the NIOSH epidemiologic research program of occupational health studies involving the DOE nuclear weapons workforce may be obtained by contacting NIOSH toll free at 1-800-35-NIOSH (1-800-356-4674) or by visiting the NIOSH website for the Occupational Energy Research Program at http://www.cdc.gov/niosh/2001-133.html iii Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard Authors Kubale TL1, Daniels RD1, Yiin, JH1, Kinnes GM1, Couch J2, Schubauer-Berigan MK1, Silver SR1, Nowlin SJ1, Chen PH1 1Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health 2Westat Inc. Acknowledgments Funding for this study was provided through an agreement between the U.S. DOE and the U.S. DHHS. This technical report resulted from the cooperation and support of the U.S. Navy, DOE, and their employees and contractors. Employees from the Portsmouth Naval Shipyard (PNS) provided numerous sources of information that were required to complete this complex study. The PNS professional staff answered many telephone calls and e-mails as source information was interpreted. This study particularly benefited from the assistance of the Jeff Brann, Jim Braun, and the shipyard Human Resources staff. Ms. Barbara Bauman and Ms. Sondra Wisdom of the National Public Record Center facility provided invaluable assistance locating critical medical record files, enabling an analysis of work-related medical X-ray exposure. Current and former staff at DOE headquarters, including Marsha Lawn, Gerry Petersen, and Heather Stockwell, provided ongoing encouragement for completion of the study. Former NIOSH scientists Robert Rinsky, William Murray, and Tim Jiggins carried out initial epidemiological, health physics, and industrial hygiene work on the study. We are grateful to the many current and former government and contract staff working with NIOSH who have provided essential services for the collection, compilation, and validation of records and data used in this study. These include Dennis Zaebst, David Back, Kevin Hubbard, Dianne Reeder, Melissa Tolson, Kim Collins, Susan Freking, and Donna Pfirman, who was instrumental in the preparation of this report. The quality of this report was substantially improved as a result of technical reviews that were provided by colleagues within NIOSH, including David Utterback, James Deadens, Dennis Zaebst, and Erin Wickliff, as well as scientific peers outside of NIOSH, Rick Hornung and Robert Rinsky. Finally, Drs. Buncher, Lockey, Rice, Rinsky, and Spitz from the Department of Environmental Health at the University of Cincinnati provided invaluable review, advice, and guidance to the study team. iv Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard Abstract Objective To determine if there is an association between occupational exposure to external ionizing radiation and leukemia mortality among civilian Portsmouth Naval Shipyard workers after potential confounders and effect modifiers such as solvent exposure, and time since exposure are considered. Methods This study employs a nested case-control design and includes 115 leukemia cases and 460 controls. Among the cases and controls, 201 (35%) were monitored for radiation exposure. Badge doses and exposures to work-required medical x-rays were included in the analysis. Benzene and carbon tetrachloride exposure was assessed using workers’ job information and industrial hygiene records. Conditional logistic regression was used to analyze the exposure-response relationship between external ionizing radiation exposure and leukemia mortality. Results A significant positive association was found between leukemia mortality and external ionizing whole-body radiation exposure (OR= 1.08 at 10 mSv; 95% CI=1.01, 1.16) adjusting for gender, radiation worker status and solvent exposure duration. The latter factor (OR= 1.03 at one year of exposure; 95% CI=1.01, 1.06) was also significantly associated with leukemia mortality. The incorporation of estimated doses from work- related medical x-ray exposures did not change the leukemia risk estimate. Significantly different exposure-response trends were observed in the 2.5 – 5 years since last exposure category compared to the > 10 years since last exposure category. The choice of categories for time since last (radiation) exposure (TSLE) classification did not greatly alter these findings. In this study the results using a linear ERR model estimate an excess relative risk of 23% (95% CI = 3%, 88%) per 10 mSv of external radiation exposure from occupational sources after potential confounders were considered in the analysis. The excess relative risk has previously been estimated at between -4.1% and 19.0% at 10 mSv in other epidemiologic studies of workers exposed to penetrating ionizing radiation (Fraser et al., 1993) and approximately 4% for individuals in the Japanese Life Span Study who were simultaneously exposed at various ages and developed diseases at different times after exposure (BEIR V,1990; Schubauer-Berigan and Wenzl, 2001). v Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard Conclusion We observed a positive association between leukemia mortality and increasing external whole-body ionizing radiation exposure, adjusting for radiation worker status and solvent exposure duration. A significant exposure response between leukemia mortality and the duration of time workers were employed in job categories where solvent exposures were probable was also observed. However, solvent exposure was not a confounder of the association between radiation exposure and leukemia risk. vi Nested Case-Control Study of Leukemia and Ionizing Radiation at the Portsmouth Naval Shipyard Table of Contents Disclaimer........................................................................................................................... ii Preface................................................................................................................................iii Authors..............................................................................................................................