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An Assessment of Radiation-Associated Risks of Mortality from Circulatory Disease in the Cohorts of Mayak and Sellafield Nuclear Workers

Research output: Contribution to journalArticle

Original languageEnglish
Article numberRR4468R2
Pages (from-to)371-388
Number of pages18
JournalRadiation Research
Volume189
Issue number4
Early online date1 Mar 2018
DOIs
DateAccepted/In press - 2 Jan 2018
DateE-pub ahead of print - 1 Mar 2018
DatePublished (current) - 1 Apr 2018

Abstract

Mortality from all circulatory disease (CD), ischaemic heart disease (IHD) and
cerebrovascular disease (CeVD) was investigated in relation to cumulative doses of external gamma radiation and of internal alpha radiation to the liver from deposited plutonium over long follow-up periods in two large cohorts of nuclear workers – the Russian Mayak Worker Cohort (MWC) and the UK Sellafield Worker Cohort (SWC). The MWC comprised 22,374 workers (74.6% males) with 5,123 CD deaths registered during 842,538 person-years of follow-up, while the SWC comprised 23,443 workers (87.8% males) with 2,322 CD deaths registered during 602,311 person-years of follow-up.
Dose estimates for external gamma radiation and internal alpha radiation to the liver were calculated via a common methodology in accordance with an agreed protocol. The mean cumulative external Hp(10) dose was 0.52 Sv for the MWC and 0.07 Sv for the SWC, while the mean cumulative internal dose was 0.19 Gy for the MWC and 0.01 Gy for the SWC. Categorical relative risks (RR) and excess relative risks (ERR) per unit dose were estimated for each cohort and for the pooled cohort when appropriate. The dose responses for CD, IHD and CeVD in relation to internal alpha-particle dose did not differ significantly from the null for either the MWC, the SWC or the pooled plutonium worker cohort. The ERR/Sv estmates in relation to external exposure were significantly raised for both cohorts (marginally so for the MWC) for CD and IHD (but not for CeVD), but
differed significantly between the two cohorts, the estimate for the SWC being around ten 3 times greater than that for the MWC. Examination of the ERR/Sv estimates for two periods of first employment at the two facilities revealed that the significant heterogeneity was confined to the earlier sub-cohorts, and that the estimates for the later sub-cohorts were compatible. The two sub-cohorts for the later first-employment periods were pooled, producing risk estimates that were raised, but not significantly so: ERR/Sv for CD, IHD and CeVD of 0.22 (95% CI: -0.01, 0.49), 0.22 (95% CI: -0.06, 0.57) and 0.24 (95% CI: -0.17, 0.80), respectively. The reasons for the complex pattern of results found in this study
are unclear. Among potential explanations are the influence of differences in background CD mortality rates, an effect of other occupational factors, substantial uncertainties in doses particularly during earlier periods of operations, as well as confounding and/or modifying factors that were not taken into account in the present analysis.

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