| Incidence of Leukemia, Lymphoma, and Multiple Myeloma in Czech Uranium Miners: A Case-Cohort Study Vladimír Rericha,1 Michal Kulich,2 Robert Rericha,3 David L. Shore,4 and Dale P. Sandler5 1Health Institute of the Uranium Industry, Príbram, Czech Republic; 2Department of Statistics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic; 3Center of Epidemiological Studies, Príbram, Czech Republic; 4Westat, Inc., Durham, North Carolina, USA; 5Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA Abstract
Objective: Uranium miners are chronically exposed to low levels of radon and its progeny. We investigated whether radon exposure is associated with increased incidence of leukemia, lymphoma, or multiple myeloma in this population.
Design: We conducted a retrospective case-cohort study in 23,043 uranium miners and identified a total of 177 incident cases of leukemia, lymphoma, and myeloma. Detailed information on occupational radon exposure was obtained for the cases and a randomly selected subcohort of 2,393 subjects. We used the proportional hazards model with power relative risk (RR) function to estimate and test the effects of cumulative radon exposures on incidence rates.
Results: Incidence of all leukemia combined and chronic lymphocytic leukemia (CLL) alone was positively associated with cumulative radon exposure. The RR comparing high radon exposure [110 working level months (WLM) ; 80th percentile] to low radon exposure (3 WLM ; 20th percentile) was 1.75 [95% confidence interval (CI) , 1.10-2.78 ; p = 0.014] for all leukemia combined and 1.98 (95% CI, 1.10-3.59 ; p = 0.016) for CLL. Myeloid leukemia and Hodgkin lymphoma were also associated with radon, but RRs were not statistically significant. There was no apparent association of radon with either non-Hodgkin lymphoma or multiple myeloma. Exposure to radon and its progeny was associated with an increased risk of developing leukemia in underground uranium miners. CLL, not previously believed to be radiogenic, was linked to radon exposure.
Key words: chronic lymphocytic leukemia, ionizing radiation, leukemogenesis, occupational exposure, radon. Environ Health Perspect 114:818-822 (2006) . doi:10.1289/ehp.8476 available via http://dx.doi.org/ [Online 26 January 2006]
Address correspondence to M. Kulich, Department of Probability and Statistics, Faculty of Mathematics and Physics, Charles University, Sokolovská 83, CZ-186 75 Praha 8, Czech Republic. Telephone: 420 221 913 229. Fax: 420 222 323 316. E-mail: kulich@karlin.mff.cuni.cz We thank the Health Institute of the Uranium Industry and the Uranium Industry Concern for providing exposure data and facilitating access to records maintained by government agencies. This work was supported through the Intramural Research Program of the NIEHS and by a contract from the NIEHS awarded to the Center of Epidemiological Studies. The authors declare they have no competing financial interests. Received 7 July 2005 ; accepted 26 January 2006.
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