Department of Pathology, People’s Friendship University of Russia, Russian Federation

*Address for Correspondence:Jargin SV, Department of Pathology, People’s Friendship University of Russia, Russian Federation Email Id: sjargin@mail.ru

Submission:22-August-2024 Accepted:10-September-2024 Published:13-September-2024

Copyright: © 2024 Jargin SV. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Keywords:East Urals Radioactive trace; ionizing radiation; cerebro-vascular diseases; cardiovascular diseases; cataracts; lens opacity

This review is focused on the radioactive contamination in the Urals, where the consequences have been more serious in the long run than those after the Chernobyl accident. Mayak Production Association, constructed in 1948, has been the first plutonium manufacturing site in the Soviet Union. The difference between contaminations in the Urals and Chernobyl is that the latter was an accident, but the former - a radioactive contamination tolerated since 70 years with several accidents in between. The tendency to overestimate health-related risks from low-dose low-rate exposures has been noticed in Chernobylrelated studies since approximately 1990 and in the research from the Urals since 2005. Cancer-related research has been commented previously. Selected cardio-, cerebro-vascular and ophthalmological conditions are discussed here. The rate of self-reporting correlates with dose estimates and awareness about radiation-related risks, the latter being associated with the work experience at the nuclear industry or residence in contaminated areas, and hence with the accumulated dose. Individuals informed of their higher doses would more often seek medical advice and on average more thoroughly examined. As a result, lens opacities and other pathological conditions are diagnosed in exposed people earlier than in the general population. This explains the dose-effect correlations reported for the incidence of cataracts but not for the frequency of cataract surgeries. Analogously, different pathological conditions are more often detected in exposed people. Results of bioassays are generally not supportive of harmful effects of low doses with possible exception of genetically modified animals. Mechanisms of damage at low doses remain speculative and the evidence inconclusive. The harm caused by anthropogenic radiation would tend to zero with a dose rate decreasing down to the level of natural background. Admittedly, irradiation may act synergistically with other noxious factors. Therefore, the optimal approach to the radiation protection is “as low as reasonably practicable”. Excessively strict regulations would cause some industries and modern technologies relocating to countries with less legalistic traditions. The environmental movement was founded on economic prosperity and complacency. When the global peace is threatened, the attitude should change.

Since many years we have tried to demonstrate that certain scientific writers and environmental campaigners act in accordance with the interests of governments selling petroleum and natural gas [1,2]. Most evident is this tendency in regard to ionizing radiation; while the overestimation of medical and environmental side effects of nuclear energy contributes to its strangulation [3], supporting appeals to dismantle nuclear power plants (NPPs). The dismantling of nuclear facilities is a complex affair; the work may span decades exceeding the building time [4]. The cost of dismantling each NPP may reach into billions of dollars [5]. The use of atomic energy for the electricity production is on the agenda today due to increasing needs of the growing humankind. The environmental damage is maximal for coal and oil, lower for gas and much lower for atomic energy - the cleanest and practically inexhaustible energy resource [3,6].

This review is focused on the radioactive contamination in the Urals, where the consequences have been more severe in the long run than those after the Chernobyl accident [1,2]. Mayak Production Association (MPA), constructed in 1948, has been the first plutonium manufacturing site in the former Soviet Union (SU). The dumping of radioactive materials into the Techa river, 1957 Kyshtym accident and dispersion by winds from the open repository lake Karachai (1967) led to exposures of the local population and some personnel. The East Urals Radioactive Trace (EURT) cohort includes people exposed after the Kyshtym accident. The difference between contaminations in the Urals and Chernobyl is that the latter was an accident, but the former - a radioactive contamination tolerated since 70 years with several accidents in between.

The Chernobyl catastrophe contributed to the dissolution of SU with subsequent privatization of the state property. At least, disregard for written instructions and safety rules were among the causes of the Chernobyl accident [7-10]. The number of control rods in the reactor was only half the minimum required for safe operation [11]. An emergency power system had been shut off, which is forbidden during on-line operation [4]. Purportedly, this was done to carry out an experiment [10,11], which might have been a pretext used to cover sabotage. It is known that sabotage and stupidity often go hand in hand. When some wreckers are caught, they pretend not realizing possible consequences. The crew kept violating regulations until they had run the reactor into unstable state that caused loss of control [4].

The weightiest argument against NPPs is that they are potential war targets. Therefore, military threats are reasons against the use of nuclear power for electricity production. Escalation of military conflicts contributes to the maintenance of high fossil fuel prices. This might have been one of the motives of unleashing the Ukraine war. The Chernobyl accident was exploited for the same purpose [3], followed by antinuclear protests in many countries [12,13]. In the aftermath of Chernobyl, some citizens decided that it was time for nuclear moratorium [4,14].

The tendency to overestimate health-related risks from lowdose exposures has been noticed in Chernobyl-related studies since approximately 1990 [15-17] and in the research from the Urals since 2005; commented previously [1,2,18,19]. In earlier Russian publications no cancer incidence elevation was reported in populations with mean total exposures ≤0.5 Sv or among MPA employees in general [20-25]. The absolute risk of leukemia per 1 Gy and 10000 man-years was found to be 3.5-fold smaller in the Techa river cohort compared to the Life Span Study (LSS) of atomic bomb survivors in Hiroshima and Nagasaki. This was reasonably explained by a higher impact of the acute exposure compared to protracted or fractionated ones. Later on, the same scientists started claiming similar risks for cancer and other diseases in the exposed cohorts of the Urals and the LSS [26-28]. Along the same lines, an earlier study found a reduction of cancer mortality in the EURT cohort compared with the general population [23]. A review dated 2004 found the same level of both cancer-related and all-cause mortality in the EURT cohort and the control [21].

In a later report about the same population, the authors avoided direct comparisons but fitted the data into a linear model. Configurations of dose-response curves shown in this paper are inconclusive but the authors claimed an elevated cancer risk in the EURT population [29]. An unofficial directive was apparently behind this ideological shift noticed around the year 2005. Manipulations with statistics have been not unusual in the former SU [30]. Exaggeration of risks from low-dose low-rate exposures contributed to anti-nuclear resentments in other countries and strangulation of nuclear energy for the boosting of fossil fuel prices [1,2,18].

In earlier reports, an incidence elevation of cardio- and cerebrovascular conditions, if even found in MPA, Techa river and EURT populations, was not accompanied by a mortality increase [31-33]. This can be explained by a greater diagnostic effectiveness in people with higher doses, leading to a recording of mild and questionable cases. However, in a recent paper based on the MPA cohort, an increased excess relative risk (ERR) of death from ischemic heart disease was claimed for the dose range 5-50 mGy/year [34]. It seems that our preceding comments [1,2], though not cited, have been taken into account by some writers. The recent review by Koterov et al. [35] has apparently been influenced by our comments cited in [36] and commented [37]; trying, however, to shift the responsibility for biased information onto foreign experts. This can be illustrated by the following citation from the abstract: “In most sources, 2005- 2021 (publications by M.P. Little with co-workers, and others) reveals an ideological bias towards the effects of low doses of radiation … In selected M.P. Little and co-authors sources for reviews and metaanalyses observed both absurd ERR values per 1 Gy and incorrect recalculations of the risk estimated in the originals at 0.1 Gy” [35]. Of note, Koterov [36] used mistranslations with a change of meaning in his Russian-language writings, commented in [37]. It must be stressed that relevant research with participation of Dr. Little [38-40] processed the data originating from Russian co-authors. In this connection, it should be agreed that the “Russian national mortality data is likely to be particularly unreliable, with major variations in disease coding practices across the country [41,42], and should therefore probably not be used for epidemiologic analysis, in particular for the Russian worker studies considered here [43-46]” [47].

Enhanced risks of cardiovascular diseases were claimed for Chernobyl, MPA, Techa river and EURT populations, where mean dose rates have been comparable with those from the natural radiation background. There are many populated areas in the world where dose rates from the natural background are ≥10-fold higher than the global average (2.4 mSv/year) with no health risks reliably proven [48]. The mean individual annual dose to residents of the Russian Federation (RF) in 2020 ranged from 2.47 mSv (Kamchatka) to 9.06 (Altai) with an average of 4.18 mSv [49]. In the above-mentioned cohorts from the Urals the doses have been protracted over decades: the MPA workers were first employed in the years 1948-1982. For example, the mean dose of gamma-radiation was 0.54 Gy in men and 0.44 Gy among women in an MPA cohort study, where the incidence of arteriosclerosis in lower limbs correlated with the radiation dose [50]. The average doses in the Techa river cohort were 34-35 mGy while the follow-up was since the 1950s [51], so that the dose rates were compatible with those from the natural background. Apparently, the data from the Techa river cohort have not enough statistical power for a precise evaluation of dose-effect relationships. The authors themselves acknowledged that the risks for the doses ≤0.1 Gy may be lower than those calculated on the basis of a linear model [52].

In particular, the risk estimates by Azizova et al. [53] were significantly higher than those by other researchers [54]. Among members of the MPA cohort who received gamma-ray doses ≥0.1 Gy, the incidence of circulatory diseases was found to be higher than in people exposed to lower doses [55,56]. Cause-effect relationships are improbable at this level of exposure, considering the dose comparisons provided here. The UNSCEAR could not reach a final conclusion in regard to causality between exposures ≥1-2 Gy and cardiovascular diseases [57]. Apparently, the level 1-2 Gy is an underestimation as a result of the screening effect, selection, self-selection, other bias and confounding factors in the epidemiological research [1,2].

Dose levels associated with cardiac derangements in animal experiments and in humans after radiotherapy are much higher than averages in the cohorts discussed above [58-62]. Results of bioassays are generally not supportive of harmful effects of low doses, with possible exception of genetically modified animals [62,63]. In certain experimental and epidemiological studies, low doses were protective against cardiovascular and other adverse effects [61,64- 69]. In humans after radiotherapy, myocardial fibrosis developed after exposures ≥30 Gy. An increased risk of coronary disease has been noticed after radiotherapy with doses 7.6-18.4 Gy [59], which is higher than averages in the cohorts discussed above.

It has been noted in the recent review that a “diagnosis (by a physician knowing the patient’s history) could vary with dose” [39]. The same has been noticed in [1,2,18]. Mild and borderline abnormalities are more often diagnosed in individuals with higher doses due to more thorough examinations and the people’s attention to their own health. The high incidence and mortality of cardiovascular diseases in studied populations [38] can be explained by the screening effect with recording of mild cases and unsubstantiated diagnoses post mortem. At least in the former SU, there is a tendency to use cardiovascular diseases as post mortem diagnoses in unclear cases [70].

The unreliability of data on mild conditions can be confirmed by the greater risks of cerebro-vascular diseases at higher radiation doses in females than in males [71]. This agrees with the known tendency that women in RF care more than men about their health. Middleaged and elderly men are visibly underrepresented among visitors of healthcare institutions; hence the worldwide greatest sex gaps in the life expectancy: countries of the former SU are at the top of the list [72]. Accordingly, the diagnostics in women is on average more efficient. Therefore, the screening effect must be more pronounced in females than in males.

Similar tendencies have been noticed in regard to cataracts. Results of the studies reporting correlations between the cumulative radiation dose and cataract incidence among MPA workers [73-75] have been questioned [76,77]. The risk in higher dose groups starting from 0.25-0.50 Sv was found to be significantly higher than that in the control group having ≤0.25 Sv. The average doses were 0.54±0.061 Gy in males and 0.46±0.01 Gy in females [74]. Dose-effect relationships were claimed for cataracts; but the well-known association of the latter with diabetes mellitus was not confirmed [74-76]. This called into question the biological relevance of other results by the same researchers. Presumably after the critical comments [76], the data on diabetes did not reappear in a subsequent article by the same researchers [78]. Of note, there were no significant associations of the radiation dose with cataract surgeries [79]. The cataracts including mild cases not requiring surgery must have been diagnosed more frequently in individuals with higher doses due to an increased attention to their own health and/or attention on the part of medics. Earlier publications with participation of the same researchers reported that radiation-induced cataracts developed among MPA workers only after exposures ≥4 Gy [80]. A review of data from RF indicated that chronic exposures ≤ 2 Gy were not associated with cataracts [81].

In animal experiments, the doses were higher than the averages in Chernobyl, MPA and Techa river populations. Some experiments in rodents investigated low doses and suggested that genetic factors have an influence on the susceptibility to radiation-induced lens opacities [61,82,83]. According to the UNSCEAR, a minimum of 3-5 Gy is needed to produce significant opacities in animals which are, similar to humans, not prone to the cataract development. Higher doses are required if protracted or fractionated. The threshold for chronic exposures was supposed to be in the range 6-14 Gy [84]. Later on, lower thresholds and the no-threshold model have been suggested. Based predominantly on epidemiological studies, ICRP revised preceding recommendations and proposed a threshold of 0.5 Gy for low linear energy transfer radiation. However, some epidemiological studies have not supported this lower threshold for cataracts [61]. “A threshold for highly fractionated or protracted exposure was judged as <0.5 Gy mainly from one paper [85] on cataracts at 12-14 years after exposure in Chernobyl clean-up workers” [86], whereas a possibility of “underestimation of uncertainties” in dosimetry was acknowledged [85]. A threshold for chronic exposures is uncertain for lack of reliable evidence [86].

In a study of radiologic technologists, the cumulative occupational exposure was associated with self-reported cataracts, but not with the cataract surgery. “The population of radiologic technologists… is medically literate” [87]. The self-reporting might have been related to a professional awareness associated with a longer work experience and hence with a cumulative dose. A similar pattern of significant ERR for cataract morbidity but not surgery has been found in MPA workers [78,79]. This agrees with the concept of a dose-dependent diagnostic efficiency with a registration in persons with higher doses of mild cases not requiring surgery. A significantly increased risk of the cataract surgery as a function of radiation dose has been reported only in LSS [88], where the effect of acute exposure could have been indeed significant. Of note, the reports by Azizova [78,79] on “a clear and significant increased ERR/Sv in females compared to males” among MPA workers were designated as “the most striking study observing sex effects relating to radiation-induced cataract incidence” [89]. The sex differences can be attributed to a gender-related attitude in the Russian healthcare. As mentioned above, middle-aged and elderly men visit health care centers (polyclinics) on the average less frequently than women. A higher frequency of cataracts in females than in males was found also in a study of the Techa river cohort [90].

Undoubtedly, ionizing radiation is a proven cataractogen; but doses and dose rates associated with risks, i.e. potential thresholds, should be further investigated. The number of studies that provide explicit biological and mechanistic evidence at doses ≤2 Gy is small [88,91]. Some recent research used genetically manipulated or mutant animals. Such data cannot be directly extrapolated to humans. Reliable information can be obtained in large-scale bioassays.

Mechanisms of damage at low doses remain speculative and the evidence inconclusive [92,93]. Summarizing the above and previously published arguments [1,2], the harm caused by anthropogenic radiation would tend to zero with a dose rate decreasing down to a wide range level of the natural background. The damage and repair are normally in a dynamic balance. Accordingly, there must be an optimal exposure level, as it is for many environmental agents: visible and ultraviolet light, various chemical elements and compounds including products of water radiolysis [94]. Moreover, the evolutionary adaptation to a changing environmental factor would lag behind its current value. Natural background radiation has been decreasing during the life existence on the Earth [95]; so that there may be some adaptation to a higher background. There are many substances and physical factors in the environment that are toxic at some dose level. The lower anthropogenic radiation, the less would be its share compared to the natural radioactive background and other environmental factors [1,2]. There is considerable evidence in favor of hormesis [61,64-69,96-99]. Admittedly, irradiation may act synergistically with other noxa. Therefore, the petition to remove the phrase “As low as reasonably achievable” (ALARA) from the radiation safety regulations [100] is hardly justified, as exposures are unpredictable during a human life, while their effects may accumulate. However, the principle ALARP (as low as reasonably practicable) is more realistic and workable than the ALARA [101].

Nuclear power has returned to the agenda because of increasing global energy demands and declining fossil fuel reserves. NPPs emit virtually no greenhouse gases compared to fossil fuels [6]. Hopefully, nuclear fission will be replaced in the future by fusion, which is intrinsically safer. The fusion offers a potential source of clean power generation with a plentiful supply of raw materials [5,102]. Durable peace and international cooperation are needed for construction of NPPs in optimally suitable places, notwithstanding national borders, considering all sociopolitical, geographic, geologic factors, attitude of workers and engineers to their duties (exemplified by the Chernobyl accident in the Introduction above). Considering potential vulnerability of large NPPs during armed conflicts, attention should be directed to small reactors, which are generally safer and have some economic advantages [103-107]. Small mobile reactors can be used also by the military. Nuclear power is the road to a carbon free future.

The optimal approach to the radiation protection is to determine thresholds and establish regulations to ensure that doses are kept well below the thresholds [108], as low as reasonably practicable considering economical realities. Otherwise, some industries and modern technologies will flee to countries with less legalistic traditions i.e. disregard for laws and regulations [109]. The environmental movement was founded on economic prosperity and complacency. When prosperity and the global peace are threatened, the attitude must change [110].

According to a recent review, epidemiological data provide essentially no evidence of harmful effects at doses <100 mSv [111]. The value 200 mSv has been mentioned in some reviews as a level, below which a cancer risk elevation is unproven [112,113]. In the author’s opinion, the current safety regulations are exceedingly restrictive. Elevation of the limits must be accompanied by measures guaranteeing their observance. Strictly observed realistic safety norms would bring more benefit for the public health and economy than excessive restrictions that would be violated by some nations disregarding laws and regulations.

Fossil fuels are used as a political weapon today [114]. Oil and natural gas will become increasingly expensive in the long run, contributing to excessive population growth in the producing regions and poverty elsewhere. Probably not all writers and green activists exaggerating medical and ecological risks from nuclear energy do realize that they serve the interests of fossil fuel producers. Many of them have good intentions; some are ideologically biased, serve certain companies or governments. Citizens should be aware that their best intentions are exploited to disadvantage their own countries. The weightiest consideration against NPPs is that they are potential targets during armed conflicts. By analogy with the Chernobyl accident, the war damage and shutdown of the Zaporozhie NPP (the largest NPP in Europe) enhances demands for oil and gas. Apparently, one of the motives to unleash the war in Ukraine, of the militarist rhetoric and threats to use nuclear weapons [115,116], has been the strangulation of nuclear energy and boosting fossil fuel prises.

Studies of human populations exposed to low-dose low-rate ionizing radiation, though important, will hardly add much reliable information on dose-effect relationships. Some reviews analyzed together papers of different quality and reliability. The inter-study heterogeneity makes assessment of risks problematic [92,117]. Finally, political and economical interests sometimes overweighed scientific objectivity [1,2]. Screening effect, selection and ideological biases will contribute to appearance of new reports on enhanced risks from a moderate anthropogenic increase of the radiation background, which would not prove causality. Reliable results can be obtained in lifelong animal experiments. The life duration is a sensitive endpoint attributable to radiation exposures [118], which can measure net harm, if any, from low-dose exposures.

Certain writers and environmental campaigners, exaggerating medical and ecological consequences of the anthropogenic increase in the radiation background, serve the interests of fossil fuel producers. Some of them may have good intentions; others are ideologically biased or have a conflict of interest. Tendentiousness is recognizable in reports aimed at the strangulation of nuclear energy and boosting fossil fuel prices. A safe implementation of nuclear power should be managed by an authority based in developed countries. The economy must become independent from politically unpredictable nations [119], including those producing fossil fuels.

The author declares that he has no conflicts of interest.