| The Effects of Internal Radiation Exposure on Cancer Mortality in Nuclear Workers at Rocketdyne/Atomics International Beate Ritz,1,2 Hal Morgenstern,1,2 Douglas Crawford-Brown,3 and Bambi Young1 1Department of Epidemiology, School of Public Health, University of California-Los Angeles, Los Angeles, California, USA
2Center for Occupational and Environmental Health, School of Public Health, University of California-Los Angeles, Los Angeles, California, USA
3Institute for Environmental Studies and Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Abstract
We examined the effects of chronic exposure to radionuclides, primarily uranium and mixed-fission products, on cancer mortality in a retrospective cohort study of workers enrolled in the radiation-monitoring program of a nuclear research and development facility. Between 1950 and 1994, 2,297 workers were monitored for internal radiation exposures, and 441 workers died, 134 (30.4%) of them from cancer as the underlying cause. We calculated internal lung-dose estimates based on urinalysis and whole-body and lung counts reported for individual workers. We examined cancer mortality of workers exposed at different cumulative lung-dose levels using complete risk-set analysis for cohort data, adjusting for age, pay type, time since first radiation monitored, and external radiation. In addition, we examined the potential for confounding due to chemical exposures and smoking, explored whether external radiation exposure modifies the effects of internal exposure, and estimated effects after excluding exposures likely to have been unrelated to disease onset. Dose-response relations were observed for death from hemato- and lymphopoietic cancers and from upper aerodigestive tract cancers, adjusting for age, time since first monitored, pay type, and external (gamma) radiation dose. No association was found for other cancers, including cancers of the lung. Despite the small number of exposed deaths from specific cancer types and possible bias due to measurement error and confounding, the positive findings and strong dose-response gradients observed suggest carcinogenic effects of internal radiation to the upper aerodigestive tract and the blood and lymph system in this occupational cohort. However, causal inferences require replication of our results in other populations or confirmation with an extended follow-up of this cohort. Key words: cancer mortality, hematopoietic cancers, internal (alpha) radiation, lymphopoietic cancers, occupational cohort study, upperaerodigestive tract cancers. Environ Health Perspect 108:743-751 (2000) . [Online 28 June 2000] http://ehpnet1.niehs.nih.gov/docs/2000/108p743-751ritz/ abstract.html Address correspondence to B. Ritz, Department of Epidemiology, School of Public Health, UCLA, Box 951772, Los Angeles, CA 90095-1772 USA. Telephone: (310) 206-7458. Fax: (310) 206-7371. E-mail: britz@ucla.edu We gratefully acknowledge the contributions of G. Wilkinson, F. Yu, Y. Wang, J. Moncau, and T. Riggs. We especially thank R. Harrison, L. Bilick, and members of the study's advisory panel. This study was supported by a grant from the Department of Energy (subcontract 324A-8701-SO163) , which was administered by the Public Health Institute in association with the California Department of Health Services. B. Ritz was supported in part by a fellowship of the German Academic Exchange Program. Received 24 January 2000 ; accepted 11 April 2000.
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