Solid Cancer Incidence in the Techa River Incidence Cohort: 1956–2007

The aim of this work is to assess the radiogenic risk of solid cancers incidence in the members of the Urals Childhood Exposure Cohort. The cohort includes people exposed under 20 years of age as a result of two radiation accidents at the Mayak Production Association in the Southern Urals (discharges of radioactive waste into the Techa River and the formation of the East Ural radioactive trace). The number of the cohort for solid cancer incidence analysis is 31,578 individuals. All the members were postnatally exposed and some of them – in-utero. Some of their parents were exposed before conception. 2,018 solid cancers were registered on the incidence catchment area during the period 1956-2018, the total amount of person years was 818,083. The analysis was carried out by the Poisson regression method with a simple parametric excess relative risk model. 95% confidence intervals were estimated with maximum likelihood approach. Only a postnatal dose was used in the first solid cancer incidence analysis of this cohort members with due account for preconception exposure of parents. TRDS-2016 mean postnatal dose accumulated over the entire follow-up period in the stomach of cohort members was 0.047 Gy. The analysis showed linear dependence of solid cancer incidence excess relative risk on postnatal dose. Excess relative risk was 0.66/Gy, р=0.006 with a five-year latency period. While estimating excess relative risk in different age groups at the beginning of exposure, a significant risk was present only in the age group under 1 year and amounted to 2.16/Gy; р<0.02 at the onset of exposure. The present results are in agreement with the results of the solid cancer incidence risk analysis both in the Techa River Cohort of exposed In-Utero where a statistically significant excess relative risk from a postnatal dose was revealed, and with the results of risk analysis in the Japanese cohort of people exposed in-utero and in early childhood.

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Solid Cancer Incidence Risk among the Population Exposed in the East Urals Radioactive Trace over 1957–2014

Medical Radiology and radiation safety ◽

10.12737/1024-6177-2020-65-4-58-64 ◽

2020 ◽

Vol 65 (4) ◽

pp. 58-64

Author(s):

S. Silkin ◽

L. Krestinina ◽

A. Akleev

Keyword(s):

Cancer Incidence ◽

Liquid Radioactive Waste ◽

Internal Exposure ◽

Likelihood Method ◽

Solid Cancer ◽

Techa River ◽

Exposed Population ◽

Incidence Risk ◽

Radioactive Trace

Purpose: Assessment of solid cancer incidence risk in the cohort of exposed population on the territory of the East Urals radioactive trace over the period of follow-up from 1957 to 2014 with the use of the individual doses provided by the latest TRDS dosimetry system. Material and methods: The explosion of the liquid radioactive waste storage tank at the «Mayak» Production Association on 29 September 1957 led to the pollution of the territories of the Chelyabinsk and Sverdlovsk Regions and the formation of the EURT, and the population residing on its territory was subjected to protracted chronic external and internal exposure. The analyzed cohort includes 21,384 people, 2,055 of whom received additional radiation before the 1957 accident due to residing in one of the Techa River settlements. The mean dose to the stomach for the members of the EURT cohort was 36 mGy, the maximum — 1.13 Gy. The analysis was performed using the DATAB and AMFIT programs (statistical software package EPICURE). A simple parametric model of excess relative risk (ERR) was used. Statistical significance and confidence intervals were obtained using the maximum likelihood method. Results: As a result of the analysis of the solid cancer incidence risk in the EURT cohort during the 57-year follow-up period using the linear model and the 5-year latent period, a statistically significant ERR was obtained which equals to 0.052 / 100 mGy (95 % CI 0.01–0.10, p = 0.02) in the entire EURT cohort. When the group of people additionally exposed on the Techa River before the 1957 accident was excluded from the cohort, the risk became insignificant. No significant modification of the dose dependence by non-radiation factors was revealed. The obtained results are compared well with the previous studies of the exposed population in the Southern Urals which were conducted in the Urals Research Center for Radiation Medicine, as well as in the world, devoted to the study of the effects of radiation exposure on population.

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