Study of the impact of noncancer diseases on assessments of radiation risks of the cancer incidence among the Chernobyl Accident liquidators

The investigation is aimed at the analysis of the statistical dose-effect relationship between malignant neoplasms incidence rate in Russian clean-up workers (liquidators) participated in mitigation of the Chernobyl nuclear power plant accident (the Chernobyl NPP accident) consequences and radiation doses. The impact of radiation on the non-cancer diseases development in the Chernobyl liquidators was estimated as well. Radiation risks of different cancer cases were estimated considering the impact of the multimorbidity factor. The monitoring data accumulated in the National Radiation Epidemiological Register from 1986 over 2022 were used for analysis. During that period 9,755 cancer cases were detected among 69,520 male liquidators. The average personal external gamma radiation dose to liquidators, accumulated during the work period was 0.13 Gy, the maximum exposure dose was 1.4 Gy. The study used general data mining approaches that did not use hypotheses of the probabilistic laws of random variable distributions that determine the dependence of cancer diseases on radiation dose. A group of liquidators with personal doses of less than 0.15 Gy was selected as a control group. It was found that the non-cancer diseases in liquidators could both increase and decrease the radiation risk of malignant neoplasms morbidity, however, the relative changes in radiation risk do not exceed 2%. The results obtained demonstrate the stability of radiation risks estimates of cancer incidence obtained earlier in the Russian cohort of liquidators without taking into account the factor of multimorbidity.