Gudzenko N.A. Analytical epidemiological studies of stochastic radiation
exposure effects in Chernobyl clean-up workers in Ukraine. Scientific report.
Collection of scientific manuscripts.
Thesis for a scientific degree of Doctor of Science in Medicine, speciality.
03.00.01 – Radiobiology. National reseaech centre for Radiation medicine of
National Academy of Medical Sciences of Ukraine, Kyiv, 2021
The dissertation is devoted to the development of the complex methodology
of carrying out an analytical epidemiological study of stochastic medical and
biological effects of ionizing radiation in Ukraine and definition the risks of longterm
oncological and genetic effects due to irradiation during the liquidation of the
Chernobyl catastrophe. .
The necessity of analytical researches in Ukraine was substantiated, the most
important components which provide provability of such projects are defined.
Proposed methods for ensuring acceptable study power, completeness and
quality of case identification and verification of the studied diseases diagnoses,
selection of adequate dosimetry methods.
Using the proposed methodology, the studies were completed and the risks
of various forms of leukemia were analyzed, taking into account the influence of
possible modifying factors
A significant positive linear association was determined between the
cumulative dose to the red bone marrow, taking into account the 2-year lag period
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with an excess of relative risk of leukemia during 1986-2006 per 1 Gray of
exposure.
Leukemia excess relative risk per 1 Gy of expodure in 1986 – 2000 was
estimated to be 3.44 0.47 – 9.78, р<0.01, including for CLL - (ERR/Gy = 4.09;
95% CI: not estimated– 14.41) and for non-CLL leukemias (ERR/Gy = 2.73; 95%
CI: not estimated – 13.50). At the same time the ERR/Gy of leukemia for the
period 1986-2006 accounting for two years LAG-period was assessed to be 2,38
(95 % CI: 0,49 – 5,87, р = 0,004) including those for CLL cases (ERR/Gy = 2,58,
95% confidence interval 0,02 – 8,43, р = 0,047) and for non-CLL cases
(ERR/Gy = 2,21, 95% confidence interval 0,05 – 7,61, р = 0,039).
Altogether, 16% of leukemia cases (18% of CLL, 15% of non-CLL) were
attributed to radiation exposure.
After adjusting for radiation,we found no clear association of leukemia risk
with smoking or alcohol consumption but identified a two-fold elevated risk for
non-CLL leukemia with occupational exposure to petroleum (OR = 2.28; 95%
Confidence Interval 1.13; 6.79). Risks were particularly high for myeloid
leukemias. No associations with risk factors other than radiation were found for
chronic lymphocytic leukemia. The first conclusions about the excessive risk of
thyroid cancer in clean-up workers were obtained although with borderline
significance.
According to the results of studies of genetic damage that could be passed on
to the next generation, it was established that there were no excess mutations
associated with the radiation dose in the family groups involved (parents and
children / child).
The study of possible dose-dependent genetic features of CLL identified
increases in telomere length in tumor cells and mutations in telomere maintenance
genes that may play a role in the genesis of radiation-associated CLL disease.
Key words: Chernobyl accident, clean-up workers, stochastic effects, excess
relative risk, leukemia, thyroid cancer, genetic damage
