Molecular and cellular consequences of the Chernobyl accident

In this paper the results of the Chernobyl accident investigation 5-10 and 24 years after are summarized. The genomic instability, adaptive response formation, genome damage and oxidative status have been investigated. The studies were performed on cells in culture, mice, children and adults living in contaminated areas and liquidators. On cells in culture after exposition in the accident zone and culturing thereafter in laboratory conditions the cell proliferative activity decrease; the late cell death, the frequency of cells with micronuclei and giant cells increasing have been observed. In the progeny of exposed cells the enhancement of radiosensitivity has been noticed. So we can suppose that in cultured cells exposition in the zone of the accident the genomic instability is induced which results in many disturbances. At the organism level in mice exposed in the Chernobyl zone the radiosensitivity increase and the decrease of endotheliocytes density in brain tissue has been observed. On the stimulated by PHA blood lymphocytes of children the increase of the frequency of cells with micronuclei more than 2 time have been noticed. In all groups investigated, the decrease of individuals with significant adaptive response was observed. In children and adults inhabitants the increase of radiosensitivity after low dose of irradiation has been noticed. 24-year after the accident it was discovered that in liquidators lymphocytes the frequency of cells with micronuclei, with chromosome type aberrations, with DNA double strand breaks have been increased; the reactive oxygen species (ROS) were decreased in comparison with the control population. We can suppose that genomic instability induced in residents of contaminated regions and liquidators long after the accident results in the genetic apparatus damage, radiosensitivity enhancement, hypoxia that represent risk factors and increase the probability of tumour and non-tumour diseases. The development of these pathological processes may happen in much more remote periods.     

Autoimmune disorders in liqvidators 11 years after the Chernobyl accident

We studied long-lasting consequences of the low-doses irradiation on the immune system of 71 clean-up workers who participated in the emergency work after the Chernobyl Plant accident in 1986 and 25 healthy donors from Belarus. In sera of the workers the level of autoantibodies to thyroid gland antigens (thyroglobulin and microsomal fraction of thyroid gland) was increased in 48% of cases, the level of autoantibodies to lens oculis antigen was increased in 44% of cases; the level of circulating immune complexes was elevated in 55%, and the serum level of thyroglobulin in 60% of people. Immunological disorders were found without any definite clinical evidences of diseases and this allows us to consider the examined contingent as a group of risk for the development of autoimmune pathology in the future.     

Biological consequences of Chernobyl: 20 years on

The disaster at the Chernobyl nuclear power plant in 1986 released 80 petabecquerel of radioactive caesium, strontium, plutonium and other radioactive isotopes into the atmosphere, polluting 200 000 km(2) of land in Europe. As we discuss here, several studies have since shown associations between high and low levels of radiation and the abundance, distribution, life history and mutation rates of plants and animals. However, this research is the consequence of investment by a few individuals rather than a concerted research effort by the international community, despite the fact that the effects of the disaster are continent-wide. A coordinated international research effort is therefore needed to further investigate the effects of the disaster, knowledge that could be beneficial if there are further nuclear accidents, including the threat of a "dirty bomb".     

15 years after the accident at the Chernobyl Nuclear Power Plant

Health effects as a result of the accident at the Chernobyl nuclear power plant occurred in 1986 are considered in the paper. Wrong prognosis of the health effects with respect to mortality and morbidity among the population exposed to low radiation doses is shown. Proven increase in thyroid cancer cases among people who were children aged from 0 to 18 at the time of the accident is shown. Linear relationship between thyroid cancer cases and dose to thyroid ranged from 0.2 to 4.0 Gy is considered. An additional absolute risk of thyroid cancer in children varies in the range 1.9-2.6 cases per 10(4) person-year Gy. During the fifteen years following the accident no cases of acute and chronic radiation sickness have been revealed because the population living in contaminated areas received low radiation doses. Also, exposures to low radiation doses did not result in excess of malignant tumors among population. In some cases the outcomes of acute radiation sickness were as follows: radiation damages to the skin, cancer cataracts, development of oncopathology.     

Chromosome alterations in cleanup workers sampled years after the Chernobyl accident

Cytogenetic analysis performed 4-13 years after the Chernobyl accident showed an elevated frequency of acentrics, chromatid exchanges, dicentrics and rings in Chernobyl cleanup workers compared to the control group. Cytogenetic data were analyzed according to the information on exposure to radiation (the year when the cleanup workers worked at the Chernobyl station, doses rates, time elapsed since exposure to radiation, and cytogenetic examination) and some lifestyle factors. The data obtained suggested that some types of chromosome aberrations could be influenced by the action of different environmental factors or lifestyle factors. The frequency of acentrics was correlated with the age of the cleanup workers, and the increased chromatid exchange frequency was attributed to smoking. The numbers of dicentrics and rings suggested a genotoxic effect of ionizing radiation that is still present over 13 years after the exposure.     

The outcome of local radiation injuries: 14 years of follow-up after the Chernobyl accident

The Chernobyl nuclear power plant accident on April 26, 1986 was the largest in the history of the peaceful use of nuclear energy. Of the 237 individuals initially suspected to have been significantly exposed to radiation during or in the immediate aftermath of the accident, the diagnosis of acute radiation sickness (ARS) could be confirmed in 134 cases on the basis of clinical symptoms. Of these, 54 patients suffered from cutaneous radiation syndrome (CRS) to varying degrees. Among the 28 patients who died from the immediate consequences of accidental radiation exposure, acute hemopoietic syndrome due to bone marrow failure was the primary cause of death only in a minority. In 16 of these 28 deaths, the primary cause was attributed to CRS. This report describes the characteristic cutaneous sequelae as well as associated clinical symptoms and diseases of 15 survivors of the Chernobyl accident with severe localized exposure who were systematically followed up by our groups between 1991 and 2000. All patients presented with CRS of varying severity, showing xerosis, cutaneous telangiectasias and subungual splinter hemorrhages, hemangiomas and lymphangiomas, epidermal atrophy, disseminated keratoses, extensive dermal and subcutaneous fibrosis with partial ulcerations, and pigmentary changes including radiation lentigo. Surprisingly, no cutaneous malignancies have been detected so far in those areas that received large radiation exposures and that developed keratoses; however, two patients first presented in 1999 with basal cell carcinomas on the nape of the neck and the right lower eyelid, areas that received lower exposures. During the follow-up period, two patients were lost due to death from myelodysplastic syndrome in 1995 and acute myelogenous leukemia in 1998, respectively. Other radiation-induced diseases such as dry eye syndrome (3/15), radiation cataract (5/15), xerostomia (4/15) and increased FSH levels (7/15) indicating impaired fertility were also documented. This study, which analyzes 14 years in the clinical course of a cohort of patients with a unique exposure pattern, corroborates the requirement for long-term, if not life-long, follow-up not only in atomic bomb survivors, but also after predominantly local radiation exposure.     

Delayed medical consequences of the Chernobyl accident in Armenia. Assessment of life quality and accelerated biological aging of accident liquidators

In this paper, some final results of 25-year investigations carried out in Scientific Centre for Radiation Medicine and Burns MH RA (SCRMB) on the Armenian cohort of the Chernobyl accident consequences liquidators are shown. These results show that health conditions of the liquidators became worse during the whole observation period. A considerable development of both pathological states atypical of radiation damages and diseases, which may be considered as radiation-induced ones, was determined. Rise of the sickness rate of almost all organism systems, first of all, nervous, cardiovascular, respiratory and digestive ones, was observed. In 70% of liquidators the main disease was primarily detected after working on CNPP. In the intervening years, the average number of diagnoses per 1 liquidator increased from 1.5 in 1987 to 7-8 in the recent time. In addition to the detected diseases, particular functional shifts in neuropsychological and vegetative status of the liquidators were observed. The overwhelming majority of them have increased tonicity of the sympathetic vegetative nervous system, asthenic and depressive syndromes occurring in the form of weakness, somnolence, mood instability, mental capacity decrease, and memory defects. In the paper, the results of investigations aimed at clarification of changes in biological aging processes of the liquidators and assessment of their "life quality" features in terms of physical, psychical and social welfare are considered. Biological aged-related passportization in a definite part of liquidators elucidated an accelerated aging rate. The studies were performed with the help of SF-36 inquirer and indicated that health status aggravation of the liquidators also affected their life satisfaction. The "life quality" indices of the liquidators significantly concede the overall average standards by both physical health and psychical and social welfare scales.     

Results of cytogenetic studies of the consequences of the Chernobyl accident

The selected results of the cytogenetic studies of the Chernobyl accident consequences were summarised. The chromosomal aberrations were used as a method of biodosimetry for a dose assessment for victims during the initial period after the Chernobyl accident. A good correlation between doses calculated based on chromosomal aberrations (dicentrics) and severity of acute radiation syndrome observed in clinic was found. The biodosimetry based on conventional cytogenetic technique (dicentrics) has been unsuccessful for various groups (rehabilitation workers, evacuees, inhabitants of contaminated areas) sampled long time after the Chernobyl accident. The possible reasons of the failure are analysed. The original results of multiaberration cell yield observed in different cohorts of the Chernobyl victims are presented. The problems related to the phenomena are discussed.     

The effect of Chernobyl accident on the development of malignant diseases--situation after 20 years

The accident that occurred at the Chernobyl Nuclear Power Plant in 1986, released large quantities of radionuclides--among them radioiodine--into the atmosphere, thereby raising public concerns about its influence on thyroid structure and function, especially the development of malignancy. There were even reports about 700 deaths due to thyroid carcinoma in Russian Federation, Ukraine and Belarus, resulting from the accident. In this review we discussed the incidence of thyroid cancer in different parts of the world, especially in heavily contaminated countries, as Ukraine and Belarus, and the possible link between radioisotope activity in the thyroid and the development of malignancy. The study carried out in Minsk showed 40-fold increase of the incidence of thyroid cancer in the years 1986-1994, in comparison to the period 1977-1985. An increase of the incidence of thyroid cancer has generally been observed in many countries after the Chernobyl accident. We focused on the factors that may have an influence on this phenomenon, especially diagnostic tests, health care, social and environmental factors, like iodine level in water and soil. The results of molecular biology studies, e.g. RET translocation in carcinoma type RET/PTC1 in elderly and RET/PTC3 in children, and expression Ax1 and Gas6 in children were reviewed as well. We also mentioned other thyroid diseases, like nodular goitre, cysts, the disturbance of thyroid function and autoimmunity, possibly linked to the radiation after Chernobyl accident. Data obtained from the regions near Chernobyl showed no increased risk of other types of malignancy (leukaemia, Hodgkin's and non Hodgkin's lymphoma) in 1986-1996. In this article the epidemiology of thyroid diseases in Poland was also reviewed.     

On the occasion of the 20th anniversary of the accident on the Chernobyl NPP: medical consequences in Armenia

The aim of this work is the analysis of the indices of the health and of the structure of the sicknesses of the inhabitants of Armenia who took part in the liquidation of the consequences of the Chernobyl accident. Also it is the determination of possible dependence of the frequency of diseases for the most widespread classes of sicknesses on the received dose of the irradiation, according to the data of the clinical examination and dispensarysation; and also it is the revelation of the role of other factors influenced on the health indexes.     

The agroecosystems flora status in restricted zone 20 years after the Chernobyl NPP accident

The article presents the results of studying on agroecosystems flora status in restricted zone 20 years after the Chernobyl accident. There were preliminary identified 8 agroecosystems associations by Broaun-Blanquet ecologo-floristic classification: Phalacrolometum septentrionale, Agrostio tenuis Calamagrostietum epigeii, Agrostio tenuis--Elytrigietum repentis, Poo pratensis--Bromopsietum inermis, Poo pratensis--Dactylidetum glomeratae, Poo pratensis--Agrostietum tenuis, Elytrigio repentis--Poetum pratensis, Caricetum hirtae. First three associations were attributed to Agropyretea repentis class, to Agropyretalia repentis order, Convolvulo--Agropyrion union. We consider the association Phalacrolometum septentrionale as the initial stage of agroscosystems overgrowing which is continued with increase of its demonstration in association Agrostio tenuis--Calamagrostietum epigeii and Agrostio tenuis--Elytrigietum repentis. The associations Poo pratensis--Bromopsietum inermis, Poo pratensis--Dactylidetum glomeratae, Poo pratensis--Agrostietum tenuis and Elytrigio repentis--Poetum pratensis we attributed to class Molinio--Arrhenatheretea, to order Arrhenatheretalia and Festuncion pratensis union. The association Caricetum hirtae was attributed to class Plantaginetea majoris, to order Plantaginetalia majoris and to union Agrapyro--Rumicion crispi. For each of the allocated associations and rye sowing there was provided brief characteristic, including 137Cs and 90Sr radionuclids content in soil and air-dry herbage mass. During the period of studies there was marked stable soil and air-dry herbage mass contamination by radionuclides at absence of grass stabilization of studied agroecosystems. The limiting factor on using of meadow agroecosystems herbages is their high level of contamination by 90Sr. The herbage can be used only for obtaining of milk-raw material for processing.     

Twenty years after the Chernobyl accident: solid cancer incidence in various groups of the Ukrainian population

Several major international studies such as those performed on the A-bomb survivors, have shown a clear linkage between the exposure to ionizing radiation and the occurrence of various cancer types including leukemia. While these studies are mostly characterized by high dose rates, studies on populations exposed after the Chernobyl accident are in most cases characterized by low dose rates which are typical for occupational radiation protection. Here, data on more than 60,000 Ukrainian workers who participated in recovery operation works in Chernobyl in 1986–1987, more than 50,000 evacuees from the city of Prypyat and the 30 km zone, and about 360,000 residents of most contaminated territories are presented, which cover a period of observation from 1980 to 2004. For all cancers combined, statistically significant higher incidence rates than the national rates were found only for the recovery workers (standardized incidence ratio (SIR) 117.2%, 95% confidence interval: 114.1–120.3), while those for the other investigated groups were lower. In all groups under study a significant increase of thyroid cancer incidence rates has been registered. This increase appears to be associated, at least partly, with the fallout of radioiodine, and it was found not only in children, but also in adolescents and adults. For example, the most significant excess was found for male recovery workers corresponding to a factor of 8.0. It is important to keep in mind, however, that the contribution of confounding factors such as an intensified thyroid screening after the Chernobyl accident could not be quantified, in the present study. For female recovery workers there was also an excess of breast cancer over the national rates (SIR 190.6%; 95% confidence interval: 163.6–217.7%). An analysis of the two other groups (evacuees and residents of contaminated territories) gave controversial results: relative to the local standard there was a statistically significant excess, while comparison with the national level did not substantiate this conclusion.     

Reduced abundance of insects and spiders linked to radiation at Chernobyl 20 years after the accident

Effects of low-level radiation on abundance of animals are poorly known. We conducted standardized point counts and line transects of bumble-bees, butterflies, grasshoppers, dragonflies and spider webs at forest sites around Chernobyl differing in background radiation by over four orders of magnitude. Abundance of invertebrates decreased with increasing radiation, even after controlling for factors such as soil type, habitat and height of vegetation. These effects were stronger when comparing plots differing in radiation within rather than among sites, implying that the ecological effects of radiation from Chernobyl on animals are greater than previously assumed.     

The significance of cytogenetic investigation for the estimation of Chernobyl accident consequences

The results of the cytogenetic investigation of people, which were exposed to radiation in the result of the Chernobyl NPP accident, were presented. Also the possibilities of the application of cytogenetic findings for dose estimations and for the prediction of the radiation influence consequences were examined. During the period of time since 1986 till 2004 the cytogenetic investigations of 1724 liquidators participating in the liquidation works after the Chernobyl accident were carried out. The radiation dose estimated by the frequency of dicentrics in 1986 was about 0.16 Gy. The doses for liquidators were determined by the frequency of translocations (FISH method) during the period from 1992 till 1995. For liquidators who worked in Chernobyl only in 1986 the average dose of radiation was about 0.19 Gy and for liquidators who worked repeatedly during the period from 1986 till 1995 - 0.39 Gy. There was shown that during the whole period of investigation (1986-2004) the frequency of dicentrics in peripheral blood lymphocytes was significantly higher than the control level. The cytogenetic investigation of Bryansk region inhabitants which was carried out in 1992-1994 discovered heightened value in 5 times than the control one. Findings are of great importance for the prediction of ill effects of radiation and for the development of sensitive criterions for early exposure disturbances in state of health.     

Cancer risks in the Kaluga oblast of the Russian Federation 10 years after the Chernobyl accident

Cancer morbidity and mortality were studied in areas of the Kaluga oblast contaminated with radionuclides. The main objective of the study was to assess the influence of radiation exposure on existing levels of cancer morbidity and mortality. Time trends and relative population risks were analysed. Based on this analysis, it was concluded that the current levels of morbidity from cancers among the populations residing in the studied areas were primarily a result of a complex of factors which predated the exposure from the Chernobyl accident. However, there seems to be an unfavourable trend concerning malignant neoplasms of the respiratory organs for women residing in the contaminated areas. To date, no statistically significant effect of radiation on cancer morbidity (except for thyroid cancer in women) has been noted. The levels of cancer morbidity and mortality in the contaminated areas generally reflect the changes in cancer incidence in the oblast as a whole. The findings are consistent with international data on latent periods for the induction of radiogenic cancers and the biological effects for similar levels of exposure to populations residing in contaminated territories. Further studies are necessary in order to monitor possible effects that are related to the accident.