Low-dose ionizing radiation and cancer mortality among enlisted men stationed on nuclear-powered submarines in the United States Navy

Abstract

Background

Men stationed on nuclear-powered submarines are occupationally exposed to external ionizing radiation at very low levels and radiation dose for each individual is closely monitored. Little is known about ionizing radiation (IR) risks of cancer mortality for populations with levels of cumulative ionizing radiation exposure this low.

Materials and methods

This historical cohort study followed 85,033 enlisted men who had served on a nuclear-powered submarine in the U.S. Navy between 1969 and 1982 to determine patterns of cancer mortality. Occupational radiation doses were measured by badge dosimeters for each individual for all periods of Navy service potentially involving radiation exposure. Deaths were ascertained through 1995 by searches of multiple national mortality databases. Within-cohort dose-response relationships for cancer mortality were estimated using linear Poisson regression models. Individual-level smoking status was not available so cancer risks were estimated separately for cancers with and without previously published evidence of consistently moderate or strong associations with smoking.

Results

A total of 584 cancer deaths occurred during a follow-up period of up to 27 years. The mean and median cumulative occupational radiation doses received while in the Navy were 5.7 and 1.1 milliSieverts (mSv), respectively, range 0–242 mSv. Mortality Excess Relative Risks (ERRs) per 10 mSv and 95% confidence intervals (CI) were 0.053 (CI −0.03, 0.17) for all cancers, 0.052 (CI −0.03, 0.18) for all solid cancers, and 0.003 (CI −0.29, 0.30) for leukemias excluding chronic lymphocytic leukemia. The ERRs per 10 mSv were 0.052 (CI −0.07, 0.17) for cancers previously associated with smoking and 0.012 (CI −0.10, 0.12) for cancers that were not.

Conclusions

The ERR point estimates for solid cancers and leukemia were statistically compatible with those reported in previously published studies of other ionizing radiation-exposed and monitored cohorts, albeit with wide confidence intervals. This study, with high-quality measurements of in-Navy occupational external IR doses, high follow-up proportion, and detailed IR dose-response analyses, is consistent with the premise of small excess cancer risks from low-dose IR.

Keywords:

• Occupational
• external ionizing radiation risk
• cohort follow-up
• solid cancer risks
• confounding by smoking

Acknowledgments

The authors gratefully acknowledge the programming support of Yelena Afanasyeva, MS, and Jianping Huang, BS.

Disclosure statement

This work was based largely on data and exposure information provided by the sponsoring agency and all results rely on the completeness and accuracy of those data. Comments from the sponsoring agency were solicited and considered, however, data analyses and interpretation, and study conclusions are entirely the independent work of the authors. All authors declare there were no additional conflicts of interest.

Additional information

Funding

Funding was from the US Navy Contract N66604-96-C-0260.

Notes on contributors

George Friedman-Jimenez

George Friedman-Jimenez, MD, DrPH, is an occupational medicine physician, epidemiologist, Director of the Bellevue/NYU Occupational Environmental Medicine Clinic and Assistant Professor of Population Health, Medicine and Environmental Medicine at NYU Grossman School of Medicine. His research interests include occupational and clinical epidemiology and their application to prevention of work-related diseases.

Ikuko Kato

Ikuko Kato, MD, PhD, is a Professor of Oncology and Pathology, Wayne State University School of Medicine in Detroit, Michigan. She was previously at New York University, working with Dr. Roy Shore and Dr. George Friedman-Jimenez, after her postdoctoral fellowship in radiation epidemiology at International Agency for Research on Cancer.

Pam Factor-Litvak

Pam Factor-Litvak, PhD, is a Professor of Epidemiology and Vice Chair for Research in the Department of Epidemiology and Associate Dean for Research Resources at Mailman School of Public Health of Columbia University. Her research interests include the biological relationships between in-utero/early childhood exposures to heavy metals or endocrine disrupting compounds, and subsequent developmental and reproductive outcomes in late childhood, adolescence and adulthood.

Roy Shore

Roy Shore, PhD, DrPH, is a Professor Emeritus at NYU Grossman School of Medicine and formerly served as Chief of Research at the Radiation Effects Research Foundation in Hiroshima, Japan. His research interests focus on the human epidemiological effects of low dose/dose rate radiation on both cancer and noncancer outcomes. He has served as a member of the International Commission on Radiological Protection (ICRP), the U.S. National Council on Radiation Protection and Measurements (NCRP) and various task groups for UNSCEAR and the U.S. National Academy of Sciences.