Vol 63, No 4 (2023)

Radiation disturbances in the lens are considered as the third most important effects of radiation, after mortality from cancer and diseases of the circulatory system (ICRP-118). In terms of the problem of the effects of low doses radiation with low LET (up to 100 mGy), interest in the dose relationship for the induction of disturbances in the lens after irradiation increases in a linear progression, as evidenced, among other things, by the chrono-dynamics of the increase in the number of relevant reviews by years shown here (since 2007; r = 0.650; p = 0.006). However, there is still no clarification of the question of the evidence of the effect of low doses on the lens. This study, consisting of two reports, attempts to fill this gap. Since epidemiological associations to confirm causality should, if possible, meet the criterion of “Biological plausibility”, this Report 1 reviewed the work considered in thematic publications on the cataractogenic effects of the lowest doses of radiation with low LET in experiments in vitro and in animals. The extreme radiosensitivity of the lens cells, exceeding even the parameters of lymphocytes in terms of induction of DNA double-strand breaks, is confirmed in a number of works (an increase in the level of breaks is shown even for a dose of 20 mGy). However, when the dose regularities are transferred to the irradiation of mice and rats in vivo, the conclusions about the effects of low doses are not confirmed. A sample of works over more than 70 years did not reveal such effects. The three exceptions (not included in PubMed paper cited in a single source, a workshop presentation, and an arbitrary textbook mention without citation) do not serve as valid scientific sources. The singularity of these data does not fall under the criterion “Consistency of association”. The smallest threshold doses of radiation for the induction of cataractogenic effects in mice are, according to studies as early as the 1950s, ~114 mGy and ~140 mGy for X-rays. The value of 150 mGy is also called (Shafirkin A.V., Grigoriev Yu.G., 2009). However, one should adhere to the results of more recent studies, according to which, when exposed to radiation in mice, a tendency to opacity in the lens can be observed for a dose of 0.2 Gy, with a statistically significant fixation of the effect for a dose of only 0.4 Gy. Most sources in experiments on rodents report threshold doses in units of gray, with a minimum of 0.5 Gy. Thus, the effects of low doses on the lens opacity were not found in the experiment.

Radiation damage to the lens is considered to be the third most important effect of radiation, after mortality from cancer and diseases of the circulatory system (ICRP-118). In terms of the effects of low dose radiation with low LET (up to 100 mGy), interest in the problem of cataractogenic disorders is growing, although there is no clarification of the issue. In the present study, two reports attempt to fill this gap. Report 1 reviewed the work on cataractogenic effects of the lowest doses of radiation with low LET in experiments in vitro and in vivo and concluded that there was no significant confirmation of them in animal experiments; Report 2 presents the results of epidemiological studies relevant to the problem. Data are presented on the uncertainties associated with such epidemiological studies: the ambiguity of the relationship between disorders in the lens and the formation of cataracts, their dependence on age, as well as the dependence of the estimation on the accepted system for classifying opacities. These uncertainties have had the consequence that since 1977 the ICRP has proposed five successively decreasing threshold doses (limits) for lens disorders. The dose patterns for radiogenic damage to the lens in the nine exposed groups mentioned in the reviews are considered: victims of atomic bombings (LSS), liquidators of the Chernobyl accident, medical radiologists (rentgenologists, technologists), patients after computed tomography and radiotherapy, industrial radiographers, nuclear industry workers, residents living with an increased radiation background (natural and man-made), for cosmonauts/astronauts and pilots. For some groups, there were statements about the effects of low doses of radiation, however, the presence of a number of epidemiological uncertainties (reverse causality in diagnostic exposure, the contribution of radiation with high LET, UV and solar radiation in cosmonauts/astronauts and pilots, doses above 100 mGy for the upper limit of the studied range in residents, etc.) do not allow us to consider these statements as proven. Therefore, for most exposed groups, a threshold of 300 mGy should be adhered to, regardless of acute or chronic exposure, according to ICRP-118, although due to the precautionary principle, based on the data discussed in Reports 1 and 2, the limit can be reduce to 200 mGy. Exceptions are medical radiologists (rentgenologists, technologists) and industrial radiographers, for whom the cataractogenic effects of low doses (several tens of milligray; working minimum – 20 mGy) can be real. This is probably due to the direct involvement of the organ of vision in professional manipulations with radiation. It is concluded that it is expedient to limit ourselves to these two groups in the future when studying radiogenic disorders in the lens after exposure to low doses of low-LET radiation, while the other groups are unpromising in this regard.

This study was caused by accumulation of the data concerning: 1) relationship between the general reactivity of the body and radioresistance; 2) essential role of mast cells in the formation of radiobiological effects; 3) significant individual features of body radioresistance. Purpose of the study was to identify the relationship of radioresistance indicators with the state of body reactivity, manifested by constitutionally determined features of connective tissue mast cells. Natural radioresistance and modifying effect of hypoxia, hyperoxia and indralin radioprotector were considered. The study was performed on 369 white male rats weighing 215–240 g. To determine the individual characteristics of radioresistance, total and cranio-caudal irradiation of animals was performed. As a hypoxic test, hypoxic gas mixture with 8% oxygen content was used. The criteria of radioresistance were 5- and 30-day survival, weight loss, early transient disability. Index of reactivity of skin mast cells was considered as the diagnostic sign. Relationship features between the level of mast cell reactivity and radioresistance indicators were revealed. It has been shown that the minimum level of natural radioresistance is typical for animals with a high index of mast cell response to hypoxia. The modifying effect of hypoxia during irradiation was manifested in all animals. Also, the highest level of modified radioresistance was observed in rats with average values of the mast cell reactivity index. At the same time, When indralin was used, its radioprotective effect was most pronounced in the group of animals with the maximum reaction of mast cells. The radiomodifying effect of oxygen is mostly expressed in rats with the maximum values of the mast cell reactivity index and is characterized by a decrease in 5-day survival and average life expectancy. The relationship between the characteristics of mast cells and radioresistance can serve as a basis for the development of methods for predicting individual natural and modified radioresistance.

This study presents original data on the content of radionuclides of natural (cosmogenic and terrorogenic) and man-made origin in the assimilation apparatus of Scots pine (Pinus sylvestris L), which grows in the Western Caucasus (within the Karachay-Cherkessia Republic). The content of radioisotopes of beryllium (⁷ Be), potassium (⁴⁰K), thorium (²³²Th), uranium (²³⁸U) and cesium (¹³⁷Cs) was revealed in pine needles. Close correlation of radionuclide content in pine needles samples ⁷Be, ²³⁸U, ¹³⁷Cs with the height of growing places was revealed.

We studied the state of seed progeny in Scots pine populations from the Polessky State Radiation-Ecological Reserve (PGRZ), Belarus. The seed progeny of the studied populations is characterized by an increased frequency of cytogenetic disorders and abortive seeds, as well as reduced germination. At the same time, Scots pine seeds from populations that have developed for a long time under chronic irradiation are characterized by increased resistance to additional γ-irradiation. Thus, the current levels of radiation exposure at the territory of the PGRZ can inhibit the reproductive capacity of Scots pine and serve as a selection factor for increased resistance to radiation.

From the moment of its creation in 1962 to the present, the Scientific Council of the Russian Academy of Sciences for Radiobiology (originally the Scientific Council at the USSR Academy of Sciences on the complex problem “Radiobiology”) has paid great attention to the damaging effects of radiation and medical radiation protection. Already the first composition of the Council included scientists who received significant experience in the field of radiobiology during active military service in educational, scientific and clinical institutions of the USSR Ministry of Defense – T.K. Dzharakyan, P.G. Zherebchenko, G.A. Zedgenidze, A.S. Mozzhukhin, V.P. Paribok. The first chairman of the Bureau of the Council was the outstanding Soviet radiobiologist A.V. Lebedinsky, who previously led radiobiological research at the Kirov Military Medical Academy. Over the years, the Council included current and retired military doctors – I.G. Akoev, E.A. Zherbin, V.I. Legeza, A.N. Grebenyuk. The Deputy Chairman of the Council, President of the Radiobiological Society of the Russian Academy of Sciences is currently I.B. Ushakov, who for a long time headed scientific institutions specialized for military radiobiology – the State Research Test Institute of Aviation and Space Medicine of the Ministry of Defense of the Russian Federation and the State Research Test Institute of Mi-litary Medicine of the Ministry of Defense of the Russian Federation. Throughout the existence of the Council, military doctors took an active part in its work, formed and supervised relevant research in the field of military radiobiology and medical radiation protection.