Effects of factors other than Chornobyl radiation on the risk of leukemia among accidental emergency and recovery operation workers from Ukraine

*Nataliya Gudzenko, Research Center for Radiation Medicine 

Keywords: leukemia, occupational exposures, smoking, alcohol, radiation, Chornobyl

Gudzenko N.A.,a Zablotska L.B.,b Romanenko A.Ye.,a Hatch M.,c Bazyka D.A.,a Trotsyuk N. K.,a Babkina N.G.,a Mabuchi K.c

a Research Center for Radiation Medicine, Kyiv, Ukraine b Department of Epidemiology and Biostatistics, School of Medicine, University of California San Francisco, U.S.A. c Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, U.S.A.

More than 25 years have passed since the accident at the Chornobyl nuclear power plant in Ukraine. Large numbers of the general population were exposed to low doses of radiation, particularly in Belarus, the Russian Federation and Ukraine. Among them, a group of approximately 600,000 cleanup workers (about half of them from Ukraine) was exposed to potentially damaging amounts of ionizing radiation. We conducted a case-control study of leukemia occurring between 1986 and 2006 in a cohort of 110,645 Chornobyl cleanup workers from Ukraine. 137 cases of leukemia (including 79 chronic lymphocytic leukemia) were confirmed by the international panel of hematologists and pathologists and were matched to 863 controls on age at the time of interview and place of residence at the time of registration in the State Chornobyl Registry. We used a specially-designed questionnaire to collect information on lifestyle and demographic characteristics as well as information necessary for retrospective radiation dose reconstruction with the RADRUE method (detailed description of the period, type of cleanup activities and location in the Chornobyl exclusion zone). Cases and controls did not differ by education, marital and urban/ rural status, but cases were more likely to have proxy interviews compared to controls (50.4% and 5.0%, respectively, p<0.001). After adjustment for radiation dose, cases and controls did not differ on the period of the first cleanup mission in the Chornobyl exclusion zone, type of work performed in the zone or a total number of missions to the zone (all p-values>0.50). There was an indication, however, that among participants with similar radiation doses cases were more likely to have spent 4-5 weeks in the zone (OR=2.24, 95% CI: 1.12-4.47, compared to less than 2 weeks in the zone, p=0.06). Relatively few subjects worked in hazardous industries, and there was no evidence of a measurable association between occupational exposures to chemicals and/or radiation due to employment in hazardous industries before or after the cleanup work at Chornobyl and risk of leukemia, after adjusting for radiation dose received during cleanup work. Smoking and alcohol consumption also were not independently associated with the risk of leukemia. Overall, in this study leukemia was not associated with any non-Chornobyl occupational exposures or lifestyle factors.