Introduction
The occurrence of leukemia and malignant tumors are the most often remote effects of radiation. It has also been shown that the health effects of radiation might depend on the duration of the exposure [1, 2]. Damage by ionizing radiation is known to be mainly due to lipid peroxidation caused by active oxygen forms. The higher the level of the active oxygen form, the greater the oxidative damage [3, 4]. In the long term, even a small dose of radiation could cause genetic changes, oncogenesis, and physiological changes, associated with a compromised immune system and increased cellular stress [5, 6]. In contrast, it is also believed that a low dose of radiation could induce both positive and negative bioeffects, thereby reducing carcinogenesis, increasing longevity, and increasing fertility [7, 8, 9].
Absorption of energy from ionizing radiation by genetic material in the cell is known to lead to DNA damage, which in turn leads to chromosome aberrations and gene mutations. Both early and late effects of radiation has been reported to lead to organ and tissue damage caused by cell death, which in turn leads to the development of cancer. Epidemiological studies have demonstrated a dose-response relationship for the induction of cancer [10]. For instance, aberrations of the chromosomal complex of peripheral blood lymphocytes were revealed in the long term following the incidence of the leaked ionizing radiation at the Chernobyl nuclear power plant (ChNPP) [11].
The results of this study revealed a high prevalence of chronic diseases among the population living in the vicinity of radioactive waste storage facilities. The population was reported to also receive chronic irradiation as a consequence of the long term exposure to radiation, with the results of the study pointing to an almost complete absence of healthy people living in the area. Diseases of the cardiovascular, hematopoietic, respiratory, and musculoskeletal systems occupied the top places in the prevalence of diseases among the population exposed to radiation [12, 13, 14]. According to the results obtained from field and laboratory analytical studies, the authors identified the negative impact of the tailings dump (radioactive waste storage) of the Stepnogorsk mining and chemical plant (uranium mining enterprise, Republic of Kazakhstan) on the environment of adjacent areas, expressed as radionuclides contaminating the soil, water and vegetation. The population living in local radioactive areas was estimated to receive an annual effective dose of about 6.5 mSv/y, whereas the normal level from natural sources should be 1 mSv/y [15].
Recently, much has been said about the ”untargeted effects” of ionizing radiation in a remote period. Briefly, ”targetless effects” is considered the ability to transfer changes from irradiated cells (target cells for radiation exposure) to unirradiated cells. This could be considered as one of the directions of the distant effects of ionizing radiation. The authors also received new data related to the radiation ”witness effect” and adaptive response. It was found that there are 2 mechanisms - intercellular interactions and secret factors that could be transmitted at a distance. The importance of studying ”non-targeted effects” is related to the use of research results in theoretical radiobiology, as well as in radiation ecology, when studying the long-term consequences of human-made disasters [16, 17]. It has been shown that ”in radiation disasters, mankind for the first time has encountered the complex, multifactorial stress,” which includes not only the biological effects of radiation but also the psychological stress of a complex structure. Psychological manifestations and consequences of this stress have been associated with the expectation of a health catastrophe [18].
One of the most radiosensitive functions of human and animal organisms is immunological reactivity. A characteristic feature of exposure to radiation is known to be the long preservation of damages in separate parts of the immune system and its associated remote consequences and complications manifested by the development of malignant tumors [19]. Ionizing irradiation in different doses in remote periods might lead to the suppression of the innate and acquired humoral and cellular immunity. Whole-body radiation exposure at doses > 2 Gy (Gray) could cause different clinical symptoms; higher doses could be so acute that they would become life-threatening [20].
Studies on the health effects of remote exposure to ionizing radiation are relevant worldwide, including Kazakhstan; some areas have been exposed to local fallout from nuclear tests at the Semipalatinsk nuclear test site; the populations living in these areas have been exposed to internal and external exposure. People who received a specific dose of radiation while living in these areas, might also face many other daily difficulties, causing further emotional distress. Given the importance of the immune system in the formation of pathological processes, its high sensitivity, as well as the significant consequences following its compromise, we were interested in its role in the formation of pathological processes in combination with the action of emotional stress and remote period exposure to ionizing radiation.