Methodological approach to countermeasure options in rural settlements in the long terms after the accident at the Chernobyl NPP

A methodological approach for the justification of rational countermeasure options in agricultural production in the long term after the Chernobyl NPP accident is presented. The decrease in the scale of countermeasures in 1993-1996 in the most affected regions has resulted to a rise in internal exposure doses to the population. A need for further application of protective measures in the long term after the Chernobyl NPP accident is estimated. It has been shown that the remediation of some rural settlements should be continued till 2045.     

Ecosystem remediation in radioactively polluted areas: the Chernobyl experience

The ecosystems of Chernobyl nuclear accident zone, having been deeply transformed by normal long-term agricultural and forestry activity, have been damaged by irradiation after the nuclear accident of 1986 and then influenced by post-accident countermeasures. Ecosystem remediation is being undertaken in this area, including maintenance of the forests, artificial afforestation, and processes of spontaneous self-restoration of the natural coenoses. Both natural and artificial remediation of the landscapes and ecosystems at the abandoned territory improves their capacity to retain radionuclides and their ability to stabilise the processes of redistribution of radionuclides and their spread in the environment. The Chernobyl zone is a territory of great importance for studying ecosystem remediation processes and elaborating on ecological engineering technologies to correct serious environmental problems arising from radionuclides release.     

Long term effects of Chernobyl contamination on DNA repair function and plant resistance to different biotic and abiotic stress factors

Thirty years after the Chernobyl explosion we still lack information regarding the genetic effects of radionuclide contamination on the plant population. For example, are plants adapting to the low dose of chronic ionising irradiation and showing improved resistance to radiation damage? Are they coping with changing/increased pathogenicity of fungi and viruses in the Chernobyl exclusion (ChE) zone? Are plant populations rapidly accumulating mutational load and should we expect rapid micro-evolutionary changes in plants in the Chernobyl area? This review will try to summarise the current knowledge on these aspects of plant genetics and ecology and draw conclusions on the importance of further studies in the area around Chernobyl.     

Elevated frequency of abnormalities in barn swallows from Chernobyl

Ever since the Chernobyl accident in 1986, that contaminated vast areas in surrounding countries with radiation, abnormalities and birth defects have been reported in human populations. Recently, several studies suggested that the elevated frequency of such abnormalities can be attributed to poverty and stress in affected human populations. Here, we present long-term results for a free-living population of barn swallows, Hirundo rustica, demonstrating the presence of 11 morphological abnormalities in populations around Chernobyl, but much less frequently in an uncontaminated Ukrainian control population and three more distant control populations. The presence of these abnormalities in barn swallows is associated with reduced viability. These findings demonstrate a link between morphological abnormalities and radiation in an animal population that cannot be attributed to poverty and stress. The most parsimonious hypothesis for abnormalities in animal and human populations alike is that the effects are caused by the same underlying cause, viz. radiation derived from the Chernobyl accident.     

Predicting radionuclide transfer to wild animals: an application of a proposed environmental impact assessment framework to the Chernobyl exclusion zone

A number of assessment frameworks have been proposed to provide a mechanism to demonstrate protection of the environment from ionising radiation. Whilst some of these are being used for assessment purposes they have largely not been validated against field measurements. In this paper we compare the predictions of transfer parameters recommended by one of these frameworks (FASSET) with observed whole-body 90Sr and radiocaesium activity concentrations in a range of mammal and invertebrate species sampled within the Chernobyl exclusion zone. Predicted activity concentrations were generally within the observed ranges and mean predictions for reference organisms were similar to, or circa one order of magnitude higher than, the observed means. However, some predictions were more than one order of magnitude lower than observed values. No data were available to test predictions for the other radionuclides released by the Chernobyl accident. In a separate paper the outputs of this assessment will be used to estimate doses to reference organisms and compare these to observed radiation induced effects reported within the Chernobyl zone.     

Genetic effects of bystander factors from the blood sera of people irradiated as the result of the Chernobyl accident

The purpose of this work was the analysis of the effects of bystander factors from blood sera of people affected by the Chernobyl accident on human keratinocyte cell culture (HPV-G cells). A new method was developed for evaluation of the bystander factor presence in vivo in blood of the people irradiated by the Chernobyl accident. Affected population groups included liquidators of the Chernobyl accident and people living and working in areas of the Gomel region contaminated by radionuclides. The analysis has shown that bystander factors persist in Chernobyl liquidator blood samples for more than 20 years since irradiation. The data suggest that blood sera contain bystander factors, which are able to induce micronuclei and decrease the metabolic activity of HPV-G cells.     

Nucleotide variation in the p53 tumor-suppressor gene of voles from Chernobyl, Ukraine

The 1986 Chernobyl disaster contaminated vast regions of Ukraine and Belarus with a variety of radioactive isotopes and heavy metals. While over 90% of the radioactive isotopes have decayed into stable compounds, radiation levels in contaminated areas are still extraordinarily high. In fact, some rodents living near the reactor have internal 134,137Cs concentrations approaching 80 000 Bq/g. Several recent genetic analyses of vertebrates have illustrated that mutation rates of organisms exposed to radiation from Chernobyl are higher than in control groups, but none have studied DNA sequences. Nucleotide sequences of rodent mitochondrial genes were originally reported to have been hypervariable, but those results were subsequently retracted. Herein, I report the results of a pilot study to determine the extent of nucleotide variation at the p53 gene in four species of rodents (voles) from Chernobyl and from control sites. I sequenced a 788 bp region (coding and non-coding) of p53 in 30 different mice comprising four different species of Microtus. Nucleotide variation at the population level was due to deletions and substitutions; both were limited to introns. There were no significant differences between the number of haplotypes in radioactive and control populations (p=0.60). Rare or private alleles might have arisen due to unique mutational pressures at Chernobyl. Alternatively, natural selection might have favored one allele over others (i.e., a selective sweep). Neither scenario is strongly supported by these data. Thus, no apparent genetic effects of the Chernobyl disaster on the p53 gene of resident voles were revealed; more extensive surveys will be necessary to determine if mutation rates are indeed elevated in mice from Chernobyl. However, two salient points emerge; the first involves the utility of introns as markers for mutations in coding regions and the second considers the relative merits of cloning in mutation detection studies.     

Historical mutation rates predict susceptibility to radiation in Chernobyl birds

Extreme environmental perturbations are rare, but may have important evolutionary consequences. Responses to current perturbations may provide important information about the ability of living organisms to cope with similar conditions in the evolutionary past. Radioactive contamination from Chernobyl constitutes one such extreme perturbation, with significant but highly variable impact on local population density and mutation rates of different species of animals and plants. We explicitly tested the hypothesis that species with strong impacts of radiation on abundance were those with high rates of historical mutation accumulation as reflected by cytochrome b mitochondrial DNA base‐pair substitution rates during past environmental perturbations. Using a dataset of 32 species of birds, we show higher historical mitochondrial substitution rates in species with the strongest negative impact of local levels of radiation on local population density. These effects were robust to different estimates of impact of radiation on abundance, weighting of estimates of abundance by sample size, statistical control for similarity in the response among species because of common phylogenetic descent, and effects of population size and longevity. Therefore, species that respond strongly to the impact of radiation from Chernobyl are also the species that in the past have been most susceptible to factors that have caused high substitution rates in mitochondrial DNA.     

Radiological assessment of protective countermeasures in the private sector of rural settlements in the Chernobyl nuclear power plant accident area

The effectiveness of countermeasures on private farms in rural settlements of the Russian Federation affected by the Chernobyl accident for the period of 1986-2005 was assessed. The averted collective doses to the residents of these settlements and the contribution of restrictive and agricultural countermeasures to dose reduction in the rural population have been estimated.     

Species richness and abundance of forest birds in relation to radiation at Chernobyl

The effects of low-level radiation on the abundance of animals are poorly known, as are the effects on ecosystems and their functioning. Recent conclusions from the UN Chernobyl forum and reports in the popular media concerning the effects of radiation from Chernobyl on animals have left the impression that the Chernobyl exclusion zone is a thriving ecosystem, filled with an increasing number of rare species. Surprisingly, there are no standardized censuses of common animals in relation to radiation, leaving the question about the ecological effects of radiation unresolved. We conducted standardized point counts of breeding birds at forest sites around Chernobyl differing in level of background radiation by over three orders of magnitude. Species richness, abundance and population density of breeding birds decreased with increasing level of radiation, even after controlling statistically for the effects of potentially confounding factors such as soil type, habitat and height of the vegetation. This effect was differential for birds eating soil invertebrates living in the most contaminated top soil layer. These results imply that the ecological effects of Chernobyl on animals are considerably greater than previously assumed.     

酞酸酯污染农田土壤生物修复研究进展

酞酸酯是目前世界上产量最大、应用面积最广的人工合成有机物,作为塑化剂被广泛应用于塑料制品中。近年来发现酞酸酯是一类典型的环境内分泌干扰物。随着生活中塑料制品日益增多,尤其是农用薄膜和有机肥的大量使用,农田土壤中酞酸酯污染日益加剧,酞酸酯污染土壤的修复逐渐引起国内外学者的广泛关注。生物修复具有价格低廉、效果良好和环境友好等特点,尤其适合于大面积污染农田土壤修复。从植物修复、微生物修复、植物微生物联合修复和动物修复等方面综述了国内外酞酸酯污染土壤生物修复的研究现状,并从高效修复植物筛选及机理探讨、实际污染土壤的降解菌修复研究、高效降解菌群的构建和作用机制等方面对该领域的研究进行了展望,以期为酞酸酯污染土壤的修复研究提供借鉴并拓展新的思路。     

Carotenoids, sexual signals and immune function in barn swallows from Chernobyl.

Carotenoids have been hypothesized to facilitate immune function and act as free-radical scavengers, thereby minimizing the frequency of mutations. Populations of animals exposed to higher levels of free radicals are thus expected to demonstrate reduced sexual coloration if use of carotenoids for free-radical scavenging is traded against use for sexual signals. The intensity of carotenoid-based sexual coloration was compared among three populations of barn swallows Hirundo rustica differing in exposure to radioactive contamination. Lymphocyte and immunoglobulin concentrations were depressed, whereas the heterophil:lymphocyte ratio, an index of stress, was enhanced in Chernobyl swallows compared to controls. Spleen size was reduced in Chernobyl compared to that of two control populations. Sexual coloration varied significantly among populations, with the size of a secondary sexual character (the length of the outermost tail feathers) being positively related to coloration in the two control populations, but not in the Chernobyl population. Thus the positive covariation between coloration and sexual signalling disappeared in the population subject to intense radioactive contamination. These findings suggest that the reliable signalling function of secondary sexual characters breaks down under extreme environmental conditions, no longer providing reliable information about the health status of males.     

Epidemiology of thyroid diseases in the population of the Sejny community after the atomic catastrophe in Chernobyl]

The survey carried out in 1990 covering the population of Sejny community, sponsored by the Ministry of Health and Welfare, program MZXVII, demonstrated the occurrence of goiter in 33.6% of studied persons. Such an incidence can rightly be recognized as an endemy. Predominance of cases with small or moderate enlargement of the thyroid (OB and I), low percentage of nodules (18%), and 2.8 times more frequent occurrence of goiter in women allows o characterize the endemy as mild. The percentage of goiter in this population does not differ from that found in this area before the Chernobyl disaster. However a small increase in the incidence of thyroid enlargement in a group of boys of age between 17 and 19 years, and an increase in percentage of nodular goiter in whole population was noted. The questionnaire studies confirmed in addition a high effectiveness of mass iodine prophylaxis introduced after the atomic disaster, especially in the population of developmental age. However, because of the latency period concerning the possible effects, the results obtained will be verified in the course of long-term prospective studies.     

Elevated frequencies of hypoxanthine phosphoribosyltransferase lymphocyte mutants are detected in Russian liquidators 6 to 10 years after exposure to radiation from the Chernobyl nuclear power plant accident

This study was conducted to determine whether the frequency of hypoxanthine phosphoribosyltransferase (HPRT) deficient lymphocyte mutants would detect an effect of radiation exposure in a population of Russians who were exposed to low levels of radiation while working in 1986 and 1987 as liquidators cleaning up after the Chernobyl nuclear power reactor accident. The HPRT lymphocyte cloning assay was performed on peripheral blood lymphocytes collected between 1992 and 1996 from 142 liquidators and 66 Russian controls, and between 1989 and 1993 from 231 American controls. Russian and American controls were not significantly different for either cloning efficiency or mutant frequency (MF); inclusion of both sets of controls in the analysis increased the ability to detect a Chernobyl exposure effect in the liquidators. After adjusting for age and smoking, the results revealed no significant difference in cloning efficiency of Chernobyl liquidators relative to Russian controls but a significant, 24% increase in liquidator HPRT mutant frequency over Russian controls (90% confidence interval was 7% to 45% increase). The analytical method also accounted for differences in precision of the individual estimates of log CE and log MF and accommodated for outliers. The increase in HPRT mutant frequency of liquidators is an attribute of the exposed population as a whole rather than of individuals. These results demonstrate that, under appropriate circumstances, the HPRT specific locus mutation assay of peripheral blood lymphocytes can be used to detect a semi-acute, low dose radiation exposure of a population, even 6 to 10 years after the exposure.     

Lithuanian cohort of Chernobyl cleanup workers: Cancer incidence follow-up 1986–2012

BackgroundCancer risks following radiation exposure in adulthood after Chernobyl are less studied compared to those after exposure in childhood. We aimed to evaluate cancer risk in the Lithuanian cohort of Chernobyl cleanup workers 26 years after their exposure in Chernobyl.MethodsStudy population (6707 men) was followed for cancer incidence upon return from Chernobyl till the end of 2012 by linkage procedure with the Lithuanian Cancer Registry and for migration and death – with Central Population Registry. The site-specific cancer risk in the cohort was estimated by calculating the standardised incidence ratio (SIR) with 95 % confidence interval (CI).ResultsA total of 596 cancer cases was observed in the cohort, against 584 expected (SIR 1.02; 95 % CI 0.94, 1.11). Only incidence of mouth and pharynx cancers was increased compared to the expected (SIR 1.41; 95 % CI 1.07, 1.86). Nevertheless, an increased risk of thyroid cancer was observed among cleanup workers who were younger than 30 years when entering the Chernobyl zone (SIR 2.90; 95 % CI 1.09, 7.72), whose radiation dose was above 100 milisievert (mSv) (SIR 3.13; 95 % CI 1.30, 7.52) and who had shorter duration of stay (SIR 2.30; 95 % CI 1.03, 5.13).ConclusionsOur findings are consistent with those observed in other cohorts of workers, namely, the increased risk of cancer sites related to behavioural factors. The increased risk of thyroid cancer among cleanup workers who were younger than 30 years when entering Chernobyl and whose radiation dose was above 100 mSv cannot exclude the association with the radiation exposure in Chernobyl.     

Response of the glutathione system to chronic irradiation of human population after the Chernobyl accident

A complex relationship between glutathione level in plasma in human population (children living in radionuclide-contaminated regions and the Chernobyl liquidators) exposed to chronic low-level radiation after the Chernobyl accident was demonstrated. The obtained experimental data indicate different responses of the human glutathione system to low (from 0.1 to 20 cSv) and high (from 20 to 150 cSv) doses of ionizing radiation.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 1, 2005, pp. 9–17.Original Russian Text Copyright © 2005 by Ivanenko, Burlakova.     

Plant-microbe interactions: novel applications for exploitation in multipurpose remediation technologies

Soil remediation that revitalizes degraded or contaminated land while simultaneously contributing to biomass biofuel production and carbon sequestration is an attractive strategy to meet the food and energy requirements of the burgeoning world population. As a result, plant-based remediation approaches have been gaining in popularity. The drawbacks of phytoremediation, particularly those associated with low productivity and limitations to the use of contaminant-containing biomass, could be addressed through novel biotechnological approaches that harness recent advances in our understanding of chemical interactions between plants and microorganisms in the rhizosphere and within plant tissues. This opinion article highlights three promising approaches that provide environmental and economic benefits of bioremediation: transgenics, low-input 'designer' plants and nanotechnology.     

The phospholipid composition of the liver in root voles living under different radioecological conditions

The effect of the increased natural radiation background (within some areas in Komi Republic) and man-caused radioactive contamination in the Chernobyl NPP accident zone on the composition of liver phospholipids in Microtus oeconomus inhabiting these areas was studied. The significant changes in the liver lipid composition in rodents inhabiting both the Chernobyl accident zone and the areas with the increased natural radiation background were found. The maximal changes in the liver phospholipid composition were revealed during the first year after the accident. The reverse dependence between the phosphatidyl choline/phosphatidyl ethanolamine ratio and the ratio between the sum of more readily oxidizable phospholipids and the sum of more poorly oxidizable ones was found. However, the slope of corresponding curves significantly depends on the radioactive state in the area of the population inhabitance. The conclusion about high sensitivity of the lipid composition of hepatocytes in Microtus oeconomus both to the impact of the man-caused radioactive contamination and the increased level of the natural radioactivity was drawn.     

Monte-Carlo prediction of changes in areas of west Cumbria requiring restrictions on sheep following the Chernobyl accident

Following the 1986 Chernobyl accident radiocaesium levels in sheep meat in some upland areas of the United Kingdom were above the national intervention limit. West Cumbria was one of these areas and restrictions are currently still in place. In addition to deposition from the Chernobyl accident, Cumbria has been subject to radiocaesium deposition from atmospheric nuclear weapons tests, the 1957 Windscale accident and routine releases from the Sellafield nuclear reprocessing plant. A Monte-Carlo approach has been used to try to predict areas in west Cumbria where radiocaesium activity concentrations in lamb meat would require the imposition of restrictions at different times after the Chernobyl accident. The approach models the transfer of radiocaesium from soil to vegetation, based upon soil organic matter, and from vegetation to lamb meat. Spatial inputs are soil organic matter and total post-Chernobyl (137)Cs and (134)Cs deposition; a ratio of Chernobyl (137)Cs to (134)Cs deposition has been used to differentiate Chernobyl and pre-Chernobyl (137)Cs deposition. Comparisons of predicted radiocaesium transfer from soil-vegetation and the spatial variation in lamb (137)Cs activity concentrations are good and predicted restricted areas with time after Chernobyl compare well to the restricted areas set by UK government. We predict that restrictions may be required until 2024 and that in some areas the contribution of pre-Chernobyl (137)Cs to predicted lamb radiocaesium activity concentrations is significant, such that restrictions may only have been required until 1994 as a consequence of Chernobyl radiocaesium deposition alone. This work represents a novel implementation of a spatial radioecological model using a Monte-Carlo approach.     

Chromosome aberrations of clonal origin in irradiated and unexposed individuals: assessment and implications.

Chromosome painting has proven useful for the detection of chromosomal rearrangements, although the presence of cells containing clonal aberrations can have an effect on the outcome of cytogenetic analyses (e.g. aberration frequency and chromosomal distribution studies). Cells with clonal chromosomal changes have been found in studies of both radiation-exposed Chernobyl cleanup workers ("liquidators") and healthy unexposed human subjects. We have used a simple statistical method to aid in the identification of individuals from distinct Chernobyl radiation-exposed and unexposed control populations who may possess cells containing clonal rearrangements. A chi2 value determined from the observed number of aberrations and the expected number based on chromosome length that corresponds to a probability less than 0.005 appears to be an indicator of clonality. These selected individuals can be analyzed further for clonality, thereby sparing detailed examination of the entire population. Here we present an analysis of individuals possessing clonal aberrations to assess the influence of clonality on the results of cytogenetic studies. Our results show that the subtraction of clonal events from the chi2 calculation for the "outliers" results in nearly all of these values losing their statistically significant deviation from proportionality. These adjustments can also be made to prevent the overestimation of frequencies of chromosome aberrations for biodosimetry. The frequency of clonal aberrations appears to increase as a function of age in control subjects, whereas an age effect was not evident in Chernobyl liquidators. This suggests that spontaneous and radiation-induced clonal expansion are occurring in control subjects and liquidators, respectively.