A nested case control study of leukaemia and ionising radiation at the Portsmouth Naval Shipyard.
Kubale T; Daniels R; Yiin J; Kinnes G; Couch J; Schubauer-Berigan M; Silver S; Nowlin S; Chen P
Occup Environ Med 2005 Nov; 62(11):e25
Introduction: Previous studies of workers at the Portsmouth Naval Shipyard (PNS) produced differing results for the relation between external ionising radiation exposure and leukaemia mortality. This case control study analysed this relation using novel exposure assessment methods for external radiation, including work related medical x rays. The study also included more thorough evaluation of benzene and carbon tetrachloride exposures. Methods: This study employed a nested case control design, with 115 leukaemia cases and 460 age matched controls. Radiation exposures from all occupational sources including work related medical x rays were assessed for the analysis. The potential for benzene and carbon tetrachloride exposure was assessed using workers' job information and industrial hygiene records. Conditional logistic regression was used to analyse the exposure-response relation between external ionising radiation exposure and leukaemia mortality. Results: A significant positive association was found between leukaemia mortality and external ionising whole-body radiation exposure (OR = 1.08 at 10 mSv; 95% CI 1.01 to 1.16) adjusting for sex, radiation worker status, and benzene or carbon tetrachloride exposure duration. Benzene or carbon tetrachloride exposure duration was also found to be significantly associated with leukemia mortality (OR = 1.03 at one year of exposure; 95% CI 1.01 to 1.06). The incorporation of estimated doses from work related medical x-ray exposures did not change the leukaemia risk estimate per unit of exposure. Conclusions: This study found that workplace exposure to external ionising radiation was associated with increased risk of death from leukaemia among PNS workers. Although confidence intervals are wide, the estimates of risk per unit of exposure found in this study are greater than those observed in the extensive risk analyses of A-bomb survivor and medical therapy studies.
Radiation; Shipyard-workers; Shipyards; Ionizing-radiation; Benzenes; X-ray-absorption; Medical-examinations; Mortality-data; Exposure-assessment; Statistical-analysis; Risk-analysis; Leukemogenesis; Blood-disorders; Chlorinated-hydrocarbons
National Institute for Occupational Safety and Health, Division of Surveillance, Hazard Evaluations, and Field Studies, 4676 Columbia Parkway, Cincinnati, OH 45226
Occupational and Environmental Medicine