Chronic low-dose exposure in the Techa River Cohort: risk of mortality from circulatory diseases
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ORIGINAL PAPER
Chronic low-dose exposure in the Techa River Cohort: risk of mortality from circulatory diseases Lyudmila Yurievna Krestinina • Svetlana Epifanova • Stanislav Silkin • Lyudmila Mikryukova • Marina Degteva • Natalia Shagina • Alexander Akleyev
Received: 7 January 2012 / Accepted: 21 October 2012 / Published online: 4 November 2012 Ó Springer-Verlag Berlin Heidelberg 2012
Abstract The aim of the present study was to analyze the mortality from circulatory diseases for about 30,000 members of the Techa River cohort over the period 1950–2003, and to investigate how these rates depend on radiation doses. This population received both external and internal exposures from 90Sr, 89Sr, 137Cs, and other uranium fission products as a result of waterborne releases from the Mayak nuclear facility in the Southern Urals region of the Russian Federation. The analysis included individualized estimates of the total (external plus internal) absorbed dose in muscle calculated based on the Techa River Dosimetry System 2009. The cohort-average dose to muscle tissue was 35 mGy, and the maximum dose was 510 mGy. Between 1950 and 2003, 7,595 deaths from circulatory diseases were registered among cohort members with 901,563 person years at risk. Mortality rates in the cohort were analyzed using a simple parametric excess relative risk (ERR) model. For all circulatory diseases, the estimated excess relative risk per 100 mGy with a 15-year lag period was 3.6 % with a 95 % confidence interval of 0.2–7.5 %, and for ischemic heart disease it was 5.6 % with a 95 % confidence interval of 0.1–11.9 %. A linear ERR model provided the best fit. Analyses with a lag period shorter than 15 years from the beginning of exposure did not reveal any significant risk of mortality from either all circulatory diseases or ischemic heart disease. There was no evidence of an increased mortality risk from cerebrovascular disease (p [ 0.5). These results should be
L. Y. Krestinina (&) S. Epifanova S. Silkin L. Mikryukova M. Degteva N. Shagina A. Akleyev Urals Research Center for Radiation Medicine, 68-a, Vorovsky St., Chelyabinsk 454076, Russia e-mail: [email protected]
regarded as preliminary, since they will be updated after adjustment for smoking and alcohol consumption. Keywords Techa River Cohort Mortality Circulatory diseases Excess relative risk
Introduction Influence of low to moderate doses of exposure to ionizing radiation on the development of non-cancer effects, and in particular on diseases of the circulatory system (DCS), has remained controversial. A detailed study of non-cancer mortality and mortality from DCS among atomic bomb survivors was presented in 2003 (Preston et al. 2003) and later (Shimizu et al. 2010). These works provide clear-cut evidence for a linear dependence of death rates on weighted absorbed dose (where the neutron absorbed dose was given a weight of 10) suggesting an excess risk even at low dose within the range 0–4 Sv. However, it is noted in both papers that there is no direct evidence of radiat
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