Nested case-control study of leukemia among a cohort of persons exposed to ionizing radiation from nuclear weapon tests in kazakhstan (1949-1963).
PURPOSE: A unique opportunity for epidemiological studies of cancer and other health effects of radiation exposures exists around the Semipalatinsk Nuclear Test Site in Kazakhstan. The present study is the first analysis of leukemia risk among the residents of downwind settlements exposed to radioactive fallout from atmospheric nuclear weapon tests (1949-1963) and followed up from 1960 to 1998.METHODS: Within the cohort of 10,000 exposed subjects a case-control study was nested, including 22 leukaemia cases (except chronic lymphoid leukemia) and 132 controls individually (1:6 ratio) matched by birth year and sex. Leukemia deaths were identified by death certificates and diagnoses were verified by hospital records. The individual dose including internal and external exposure assessment was estimated according to the residency and age at exposure. All odds ratios were adjusted for ethnicity (Russian or Kazakh) as an independent variable.RESULTS: The median dose of exposure for all subjects was 0.89 Sv ranging from 0.01 to 5.71 Sv. A nearly two-fold increased risk of leukemia was found (OR = 1.91; 95% CI = 0.38 to 9.67) for persons exposed to doses of >2.0 Sv as compared to those exposed to <0.5 Sv, but no increase in risk with the dose was found for those exposed to doses lower than 2 Sv. Detailed evaluation of dose-response showed an excess relative risk for leukemia of 10% per 1 Sv of additional exposure.CONCLUSIONS: Our findings suggest that there is an increased risk of leukemia among those exposed to >2 SV as compared to those exposed to <0.5 Sv, but this could have been a chance finding due to the small number of cases and low statistical power.
Abylkassimova
Z
Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD, Institute for Radiation Medicine and Ecology, Semipalatinsk, Kazakhstan, and BfS Institute for Radiation Hygiene, Munich, Germany
Gusev
B
Grosche
B
Bauer
S
Kreuzer
M
Trott
K