The Ukrainian-American study of leukemia and related disorders among Chornobyl cleanup workers from Ukraine: I. Study methods.

There are relatively few data on the risk of leukemia among those exposed to external radiation during cleanup operations after the Chornobyl nuclear accident, and results have not been consistent. To investigate this further, we assembled a cohort of 110,645 male cleanup workers from Ukraine and identified cases of leukemia occurring during the period 1986 to 2000. Detailed interviews were conducted and individual bone marrow doses estimated using a new time-and-motion method known as RADRUE described in companion paper II. For the initial analyses we used a nested case-control approach with a minimum of five controls per case, matched for year of birth, oblast (region) of registration, and residence. All identified cases were reviewed by an international panel of experts; 87 of 111 were confirmed. The dose-response analysis and results are given in companion paper III. As background, we describe herein the design, procedures, outcome of case finding and confirmation, control selection, dose estimation and interviewing of subjects.