Medical Radiology and Radiation Safety. 2025. Vol. 70. № 5

DOI:10.33266/1024-6177-2025-70-5-70-74

A.M. Korelo, M.A. Maksioutov, S.Yu. Chekin, K.A. Tumanov,
N.V. Shchukina, E.V. Kochergina, O.E. Lashkova, N.S. Zelenskaya, V.K. Ivanov

Influence of Exposure Duration on Radiation-Induced Morbidity Among Liquidators of the Consequences of the Accident at the Chernobyl Nuclear Power Plant

А.F. Tsyb Medical Radiological Research Centre, Obninsk, Kaluga region, Russia

Contact person: A.M. Korelo, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

ABSTRACT

Purpose: To assess the effect of exposure duration on radiation-induced morbidity.

Material and methods: Retrospective cohort study of the influence of the duration of exposure on radiation-induced morbidity of the participants of the liquidation of the Chernobyl accident consequences according to the data of the National Radiation Epidemiologic Register. The SOLID cohort consisted of 67616 persons who had no diagnoses of “solid malignant neoplasms other than skin cancer” before January 1, 1992. The HEART cohort consisted of 69456 persons who had no cardiovascular diseases before January 1, 1988: ischemic heart disease, heart failure, conduction and heart rhythm disorders, heart valve disease and lesions. The end of follow-up is 2023. Observed cohort morbi-
dity was modeled by assuming that the number of disease cases had a Poisson distribution. Three models were tested: non-radiation risk, li-
near relative radiation risk, and exposure time-adjusted linear relative radiation risk. Non-radiation incidence was modeled as an exponential dependence on the region of residence, age at the time of exposure, and calendar year of observation. Adjustment for the time of radiation exposure was modeled as an exponential function. Estimates of coefficients of morbidity models were obtained by the maximum likelihood method using the programming language for statistical calculations R and the packages for R gnm and data.table.

Results: The linear relative radiation risk model was preferred over the non-radiation risk model for both the SOLID cohort (p<0.001) and the HEART cohort (p<0.001). The excess relative radiation risk per 1 Gy was 0,67 (95 % confident interval (CI): 0.37; 1.00) for the SOLID cohort and 0,66 (95 % CI: 0.51; 0.81) for the HEART cohort. Adjustment for exposure time was not statistically significant for the SOLID cohort (–0.10; 95 % ДИ: –0.46; 0.26; p=0.38) but statistically significantly less than 0 for the HEART cohort (–1.19; 95 % ДИ: –1.63; –0.76; p<0.001) – the longer the duration of exposure, the smaller the excess relative radiation risk per 1 Gy.

Conclusion: In the studied cohort of Russian participants of the Chernobyl accident consequences liquidation, a sixfold decrease of the relative radiation risk coefficient per unit dose with increasing duration of exposure from 1 to 100 days was revealed for the incidence of cardiovascular diseases (ischemic heart disease, heart failure, conduction and heart rhythm disorders, heart valve diseases and lesions). For the incidence of solid malignant neoplasms (excluding non-melanoma skin cancer) no statistically significant dependence of the relative radiation risk coefficient on the duration of exposure was revealed. The obtained results indicate significant differences in radiation-epidemiologic peculiarities of malignant neoplasms and tissue reactions (heart diseases).

Keywords: Chernobyl accident liquidators, National Radiation Epidemiological Register, morbidity, dose, dose rate, external gamma radiation, exposure duration, cohort study, radiation risk

For citation: Korelo AM, Maksioutov MA, Chekin SYu, Tumanov KA, Shchukina NV, Kochergina EV, Lashkova OE, Zelenskaya NS, Ivanov VK. Influence of Exposure Duration on Radiation-Induced Morbidity Among Liquidators of the Consequences of the Accident at the Chernobyl Nuclear Power Plant. Medical Radiology and Radiation Safety. 2025;70(5):70–74. (In Russian). DOI:10.33266/1024-6177-2025-70-5-70-74

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Conflict of interest. The authors declare no conflict of interest.

Financing. The study had no sponsorship.

Contribution. Article was prepared with equal participation of the authors.

Article received: 20.05.2025. Accepted for publication: 25.06.2025.