Mortality from leukemia, cancer and heart disease among U.S. nuclear power plant workers, 1957–2011

Abstract

Background

The aim of the Million Person Study of Low-Dose Health Effects (MPS) is to examine the level of radiation risk for chronic exposures received gradually over time and not acutely as was the case for the Japanese atomic bomb survivors. Nuclear power plant (NPP) workers comprise nearly 15 percent of the MPS. Leukemia, selected cancers, Parkinson’s disease, ischemic heart disease (IHD) and other causes of death are evaluated.

Methods and material

The U.S. Nuclear Regulatory Commission’s Radiation Exposure Information and Reporting System (REIRS) and the Landauer, Inc. dosimetry databases identified 135,193 NPP workers first monitored 1957–1984. Annual personal dose equivalents [Hp(10)] were available for each worker. Radiation records from all places of employment were sought. Vital status was determined through 2011. Mean absorbed doses to red bone marrow (RBM), esophagus, lung, colon, brain and heart were estimated by adjusting the recorded Hp(10) for each worker by scaling factors, accounting for exposure geometry and energy of the incident gamma radiation. Standardized mortality ratios (SMR) were calculated. Radiation risks were estimated using Cox proportional hazards models.

Results

Nearly 50% of workers were employed for more than 20 years. The mean duration of follow-up was 30.2 y. Overall, 29,124 total deaths occurred, 296 from leukemia other than chronic lymphocytic leukemia (CLL), 3382 from lung cancer, 140 from Parkinson’s disease and 5410 from IHD. The mean dose to RBM was 37.9 mGy (maximum 1.0 Gy; percent >100 mGy was 9.2%), 43.2 mGy to lung, 43.7 mGy to colon, 33.2 mGy to brain, and 43.9 mGy to heart. The SMRs (95% CI) were 1.06 (0.94; 1.19) for leukemia other than CLL, 1.10 (1.07; 1.14) for lung cancer, 0.90 (0.76; 1.06) for Parkinson’s disease, and 0.80 (0.78; 0.82) for IHD. The excess relative risk (ERR) per 100 mGy for leukemia other than CLL was 0.15 (90% CI −0.001; 0.31). For all solid cancers the ERR per 100 mGy (95% CI) was 0.01 (–0.03; 0.05), for lung cancer −0.04 (–0.11; 0.02), for Parkinson’s disease 0.24 (–0.02; 0.50), and for IHD −0.01 (–0.06; 0.04).

Conclusion

Prolonged exposure to radiation increased the risk of leukemia other than CLL among NPP workers. There was little evidence for a radiation association for all solid cancers, lung cancer or ischemic heart disease. Increased precision will be forthcoming as the different cohorts within the MPS are combined, such as industrial radiographers and medical radiation workers who were assembled and evaluated in like manner.

Keywords:

• Epidemiology
• Million Person (Worker) Study
• nuclear power plant workers
• leukemia and cancer
• heart disease

Acknowledgments

We are indebted to the DOE (Nimi Rao), the NRC (Doris Lewis), the U.S. Army Dosimetry Center (William S. Harris, Jr., CHP), the U.S. Air Force Radiation Dosimetry Laboratory (Gerald M. Achenbach), and the Naval Dosimetry Center (CAPT Thad Sharp and LCDR Nakima McCormack) for facilitating linkages with their respective military dosimetry files. Special thanks to Dale Preston who provided leukemia analysis with the atomic bomb data consistent with our parameters (adult males, age range, follow-up time), and who provided insights into the power of Epicure in conducting a wide range of analyses. We are most grateful to Sara C. Howard at ORAU who provided Epicure analyses and created the graphics for Figures 2–7 in this article. The results presented herein represent the conclusions and opinions solely of the authors. Its publication does not imply endorsement by the National Council on Radiation Protection and Measurements, Vanderbilt University or any of the acknowledged agencies.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The study of U.S. nuclear power plant workers, a component of the Million Person Study, was supported in part by a research grant from the U.S. Department of Energy [Grant No. DE-SC0008944] awarded to the National Council on Radiation Protection and Measurements, which included interagency support from the U.S. Nuclear Regulatory Commission (NRC), the U.S. Environmental Protection Agency and the National Aeronautics and Space Administration (NASA)); and more recent Grants from the Department of Energy [No. DE-AU0000042 and DE-AU0000046]. Additional support included grants from the NRC [NRC-HQ‐60‐14‐G‐0011]; the Centers for Disease Control and Prevention [5UE1EH000989, 5NUE1EH001315]; NASA [NNX15AU88G, 80NSSC17M0016], and a Discovery Grant from the Vanderbilt-lngram Cancer Center. [Center no. 404-357-9682]. Contract support also was received from the Naval Sea Systems Command [N00024-17-C-4322] for dosimetry linkage.

Notes on contributors

John D. Boice

John D. Boice is past President of the National Council on Radiation Protection and Measurements and Professor of Medicine at Vanderbilt University. He is an international authority on radiation effects and served on the Main Commission of the International Commission on Radiological Protection and the United Nations Scientific Committee on the Effects of Atomic Radiation. He directs the Million Person Study of Low-Dose Health Effects.

Sarah S. Cohen

Sarah S. Cohen is a Senior Managing Epidemiologist at EpidStrategies, a Division of ToxStrategies, where she directs observational research studies in the areas of pharmacoepidemiology, nutritional epidemiology, and occupational epidemiology as well as leads large data management projects and statistical analyses. She is also an Adjunct Assistant Research Professor of Medicine in the Department of Medicine at Vanderbilt University School of Medicine. She has been a collaborator on the Million Person Study of Low-Dose Health Effects for nearly twenty years, providing analytic support as well as coauthoring numerous publications.

Michael T. Mumma

Michael T. Mumma is the Director of Information Technology at the International Epidemiology Institute and the International Epidemiology Field Station for Vanderbilt University Medical Center. He has over 20 years of experience in data analysis and conducting epidemiologic investigations. He has published on methodological topics, including geocoding and comprehensive radiation exposure assessment, and is currently developing methods to determining socioeconomic status based on residential history.

Derek A. Hagemeyer

Derek Hagemeyer, is the Associate Director for Human Health & Environment at Oak Ridge Associated Universities. He is responsible for program operations associated with human subject health and protection surveillance as well as the independent environmental assessment and verification under the DOE Oak Ridge Institute for Science and Education (ORISE). He serves as the principal investigator for the DOE Radiation Exposure Monitoring System (REMS) and the U.S. Nuclear Regulatory Commission (USNRC) Radiation Exposure Information and Reporting System (REIRS) projects.

Heidi Chen

Heidi Chen is a Research Assistant Professor of Biostatistics in the Vanderbilt Center for Quantitative Sciences. Her Ph.D. is in biomathematics from North Carolina State University and her research focuses on applying mathematical, statistical and computational methods to fit models for biological systems. Since joining the Department of Biostatistics, Vanderbilt University Medical Center in 2003, her research has involved identifying biomarkers and building models to predict disease progression and clinical outcomes for cancer patients. Heidi has been a statistical collaborator on the Million Person Study since 2013.

Ashley P. Golden

Ashley P. Golden is a biostatistician and Director of ORISE Health Studies at Oak Ridge Associated Universities where she conducts multidisciplinary projects in occupational epidemiology, radiation exposure and dosimetry, medical surveillance, and environmental assessments. She has been a collaborator on the Million Person Study of Low-Dose Health Effects for eight years.

R. Craig Yoder

R. Craig Yoder directed the technical activities and programs at Landauer, Inc. from 1983 through his retirement in 2015. In this capacity, he influenced the technologies and measurement protocols used by the Company as it delivered dosimetry services around the world. He currently is using his historical knowledge to advise the MPS epidemiologists regarding the methods to translate personal monitoring information into mean absorbed doses to various organs. He is a Council member of the National Council on Radiation Protection.

Lawrence T. Dauer

Lawrence T. Dauer is an Attending Physicist specializing in radiation protection at Memorial Sloan Kettering Cancer Center in the Departments of Medical Physics and Radiology. He is a Council and former Board member of the NCRP and served as a member of the ICRP Committee 3, Protection in Medicine. Previously, he was a Radiological Engineering Supervisor in the nuclear power industry. He is Scientific Director of the Million Person Study of Low-Dose Health Effects.