Radiation-induced effects on plants and animals: findings of the United Nations Chernobyl Forum

Radiation-induced cytogenetic and hematologic effects on aquatic biota within the Chernobyl exclusion zone

During 1998-2014 the rate of chromosomal aberrations in embryo tissues of the pond snail (Lymnaea stagnalis) and root meristems of higher aquatic plants, and also hematologic indexes of mantle liquid of the adult snails and peripheral blood of fishes in water bodies within the Chernobyl exclusion zone (EZ) was studied. The absorbed dose rate for hydrobionts from water bodies of the EZ registered in a range from 0.25 to 420 μGy h(-1) and in the reference ones - up to 0.09 μGy h(-1). The level of chromosomal aberrations in the molluscs from the most contaminated water bodies of the EZ was registered within range of 18-27% and for the molluscs from the reference lakes this index was on the average 1.5% with the maximal values 2.3%. The rate of chromosomal aberrations in root meristematic cells of higher aquatic plants from the contaminated lakes of the EZ was in range of 7-17% and in the plants from reference water bodies was not exceed 2.1%. The positive correlation between chromosomal aberration rate and absorbed dose rate in the pond snail's embryos and root meristems of higher aquatic plants in water bodies of the EZ was registered. Analysis of hemolymph structure of snails from the most contaminated water bodies showed a high rate of dead and phagocytic cells as well as decrease of the young amoebocytes quantity. Hematologic research of fish allows to determine on the one hand an insignificant changes of leukogram structure, and from the other hand a high level of red cells with different abnormalities in the peripheral blood of fishes from the water bodies with high levels of radioactive contamination. It is suppose that qualitative indexes of red cells in peripheral blood of fish are more sensitive to long-term radiation impact in comparison with elements of white blood, which can be used for conducting of the hematologic monitoring of radioactive contaminated water bodies.

Soil nematode assemblages as bioindicators of radiation impact in the Chernobyl Exclusion Zone

In radioecology, the need to understand the long-term ecological effects of radioactive contamination has been emphasised. This requires that the health of field populations is evaluated and linked to an accurate estimate of received radiological dose. The aim of the present study was to assess the effects of current radioactive contamination on nematode assemblages at sites affected by the fallout from the Chernobyl accident. First, we estimated the total dose rates (TDRs) absorbed by nematodes, from measured current soil activity concentrations, Dose Conversion Coefficients (DCCs, calculated using EDEN software) and soil-to-biota concentration ratios (from the ERICA tool database). The impact of current TDRs on nematode assemblages was then evaluated. Nematodes were collected in spring 2011 from 18 forest sites in the Chernobyl Exclusion Zone (CEZ) with external gamma dose rates, measured using radiophotoluminescent dosimeters, varying from 0.2 to 22 μGy h(-1). These values were one order of magnitude below the TDRs. A majority of bacterial-, plant-, and fungal-feeding nematodes and very few of the disturbance sensitive families were identified. No statistically significant association was observed between TDR values and nematode total abundance or the Shannon diversity index (H'). The Nematode Channel Ratio (which defines the relative abundance of bacterial- versus fungal-feeding nematodes) decreased significantly with increasing TDR, suggesting that radioactive contamination may influence nematode assemblages either directly or indirectly by modifying their food resources. A greater Maturity Index (MI), usually characterising better soil quality, was associated with higher pH and TDR values. These results suggest that in the CEZ, nematode assemblages from the forest sites were slightly impacted by chronic exposure at a predicted TDR of 200 μGy h(-1). This may be imputable to a dominant proportion of pollutant resistant nematodes in all sites. This might result from a selection at the expense of sensitive species after the accident.

Aspermy, sperm quality and radiation in Chernobyl birds

BACKGROUND

Following the Chernobyl nuclear power plant accident, large amounts of radionuclides were emitted and spread in the environment. Animals living in such contaminated areas are predicted to suffer fitness costs including reductions in the quality and quantity of gametes.

METHODOLOGY/PRINCIPAL FINDINGS

We studied whether aspermy and sperm quality were affected by radioactive contamination by examining ejaculates from wild caught birds breeding in areas varying in background radiation level by more than three orders of magnitude around Chernobyl, Ukraine. The frequency of males with aspermy increased logarithmically with radiation level. While 18.4% of males from contaminated areas had no sperm that was only the case for 3.0% of males from uncontaminated control areas. Furthermore, there were negative relationships between sperm quality as reflected by reduced sperm velocity and motility, respectively, and radiation.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that radioactive contamination around Chernobyl affects sperm production and quality. We are the first to report an interspecific difference in sperm quality in relation to radioactive contamination.

Genome-wide analysis of mutations in mutant lineages selected following fast-neutron irradiation mutagenesis of Arabidopsis thaliana

Ionizing radiation has long been known to induce heritable mutagenic change in DNA sequence. However, the genome-wide effect of radiation is not well understood. Here we report the molecular properties and frequency of mutations in phenotypically selected mutant lines isolated following exposure of the genetic model flowering plant Arabidopsis thaliana to fast neutrons (FNs). Previous studies suggested that FNs predominantly induce deletions longer than a kilobase in A. thaliana. However, we found a higher frequency of single base substitution than deletion mutations. While the overall frequency and molecular spectrum of fast-neutron (FN)–induced single base substitutions differed substantially from those of “background” mutations arising spontaneously in laboratory-grown plants, G:C>A:T transitions were favored in both. We found that FN-induced G:C>A:T transitions were concentrated at pyrimidine dinucleotide sites, suggesting that FNs promote the formation of mutational covalent linkages between adjacent pyrimidine residues. In addition, we found that FNs induced more single base than large deletions, and that these single base deletions were possibly caused by replication slippage. Our observations provide an initial picture of the genome-wide molecular profile of mutations induced in A. thaliana by FN irradiation and are particularly informative of the nature and extent of genome-wide mutation in lines selected on the basis of mutant phenotypes from FN-mutagenized A. thaliana populations.

Effects of different gamma exposure regimes on reproduction in the earthworm Eisenia fetida (Oligochaeta)

Ecological risk assessment of ionising radiation requires knowledge about the responses of individuals and populations to chronic exposures, including situations when exposure levels change over time. The present study investigated processes such as recovery and the adaptive response with respect to reproduction endpoints in the earthworm Eisenia fetida exposed to (60)Co γ-radiation. Furthermore, a crossed experiment was performed to investigate the influence of F0 parental and F1 embryonic irradiation history on the response of irradiated or non-irradiated F1 offspring. Recovery: The sterility induced by sub-chronic exposure at 17 m Gy/h (accumulated dose: 25 Gy) was temporary, and 8 weeks after irradiation the worms had regained their reproductive capacity (number of viable offspring produced per adult per week). Adaptive response: Adult worms were continuously exposed at a low priming dose rate of 0.14 mGy/h for 12 weeks (accumulated dose: 0.24 Gy), followed by 14 weeks exposure at a challenge dose rate of 11 mGy/h. The results suggest a lack of adaptive response, since there were no significant differences in the effects on reproduction capacity between the primed and the unprimed groups after challenge doses ranging from 7.6 to 27 Gy. Crossed experiment: The effects of exposure at 11 mGy/h for 21 weeks on growth, sexual maturation and reproduction of offspring, derived either from parent worms and cocoons both exposed at 11 mGy/h, or from non-irradiated parents and cocoons (total accumulated dose 44 and 38 Gy, respectively) were compared. There were no significant differences between the two exposed offspring groups for any of the endpoints. The reproduction capacity was very low for both groups compared to the controls, but the reproduction seemed to be maintained at the reduced level, which could indicate acclimatisation or stabilisation. Finally, parental and embryonic exposures at 11 mGy/h did not affect reproduction in the F1 offspring as adults.

Radiation exposure differentially affects songbird 8-hydroxy-2'-deoxyguanosine plasma profiles: ionizing radiation damage response in songbirds

The importance of understanding the effects of radiation exposure on wildlife is a critical responsibility of our stewardship of nuclear energy production. We tested the hypothesis that songbirds respond to exogenous radiation exposure with changes in plasma 8-hydroxy-2'-deoxyguanosine (8-OH-dG). We exposed two species of songbirds, house sparrows (Passer domesticus; n = 12) and song sparrows (Melospiza melodia; n = 12), to one of four acute whole-body radiation treatments: 75, 150, 300, or 600 mGy. We measured DNA damage by proxy as 8-OH-dG levels in the plasma at 0 hr (baseline), 36 hr, and 7 days post radiation. For both species, at all radiation treatments, 8-OH-dG levels increased significantly 36 hr following radiation exposure. However, songbird species differed significantly in response to treatment across time and between treatment groups. Song sparrows showed no significant changes in 8-OH-dG levels between 36 hr and Day 7. In contrast, house sparrows exposed to 300 and 600 mGy had significantly increased 8-OH-dG levels at Day 7 compared with 36 hr. This study demonstrates that in a controlled experiment, in isolation from other sources of genotoxicity, radiation exposure significantly affects songbirds. Our results suggest future research examining the effects of radiation on songbirds must consider using multiple species to assess the biological effects of radiation, as different species can show strikingly different responses to radiation dosage across time.

Abundance and diversity of aquatic macroinvertebrate communities in lakes exposed to Chernobyl-derived ionising radiation

Littoral (lake shore) macroinvertebrate communities were studied in eight natural lakes affected by fallout from the Chernobyl accident. The lakes spanned a range in (137)Cs contamination from 100 to 15500 kBq m(-2) and estimated external dose rates ranged from 0.13 to 30.7 μGy h(-1). General linear models were used to assess whether abundance of individuals, taxon richness, Berger-Parker dominance and Shannon-Wiener diversity varied across the lakes. Step-wise multiple regressions were used to relate variation in total abundance, taxon richness, Berger-Parker dominance, Shannon-Wiener diversity, taxon richness within major groups of macroinvertebrates and abundance of the more common individual taxa to the measured environmental characteristics (conductivity, pH, total hardness and phosphate; lake area, lake maximum depth and total external dose) of the lakes. No evidence was found in this study that the ecological status of lake communities has been influenced by radioactive contamination from the Chernobyl accident. Indeed, the most contaminated lake, Glubokoye, contained the highest richness of aquatic invertebrates. Taxon richness in the eight study lakes varied from 22 (Svyatskoe #7) to 42 (Glubokoye) which spans a range typical for uncontaminated lakes in the region. Since (90)Sr is readily-absorbed by Mollusca, estimated dose rates to this group exceeded those for other invertebrate groups in two lakes (Perstok and Glubokoye). However this study found no association between mollusc diversity or abundance of individual snail species and variation between lakes in the external radiation dose. Indeed Glubokoye, the lake most contaminated by (90)Sr, had the highest richness of freshwater snails per sample (an average of 8.9 taxa per sample).

The view from the trenches: part 1-emergency medical response plans and the need for EPR screening

Few natural disasters or intentional acts of war or terrorism have the potential for such severe impact upon a population and infrastructure as the intentional detonation of a nuclear device within a major U.S. city. In stark contrast to other disasters or even a "dirty bomb," hundreds of thousands will be affected and potentially exposed to a clinically significant dose of ionizing radiation. This will result in immediate deaths and injuries and subsequently the development of Acute Radiation Syndrome (ARS). Additionally, millions more who are unlikely to develop ARS will seek medical evaluation and treatment, overwhelming the capacity of an already compromised medical system. In this paper, the authors propose that in vivo electron paramagnetic resonance (EPR) dosimetry be utilized to screen large numbers of potentially exposed victims, and that this screening process be incorporated into the medical-surge framework that is currently being implemented across the nation for other catastrophic public health emergencies. The National Incident Management System (NIMS), the National Response Framework (NRF), the Target Capabilities List (TCL), Homeland Security Presidential Directives (HSPD), as well as additional guidance from multiple federal agencies provide a solid framework for this response. The effective screening of potentially-exposed victims directly following a nuclear attack could decrease the number of patients seeking immediate medical care by greater than 90%.

Effects of non-human species irradiation after the Chernobyl NPP accident

The area affected by the Chernobyl Nuclear Power Plant accident in 1986 has become a unique test site where long-term ecological and biological consequences of a drastic change in a range of environmental factors as well as trends and intensity of selection are studied in natural settings. The consequences of the Chernobyl accident for biota varied from an enhanced rate of mutagenesis to damage at the ecosystem level. The review comprehensively brings together key data of the long-term studies of biological effects in plants and animals inhabiting over 20 years the Chernobyl NPP zone. The severity of radiation effects was strongly dependent on the dose received in the early period after the accident. The most exposed phytocenoses and soil animals' communities exhibited dose dependent alterations in the species composition and reduction in biological diversity. On the other hand, no decrease in numbers or taxonomic diversity of small mammals even in the most radioactive habitat was shown. In a majority of the studies, in both plant and animal populations from the Chernobyl zone, in the first years after the accident high increases in mutation rates were documented. In most cases the dose-effect relationships were nonlinear and the mutation rates per unit dose were higher at low doses and dose rates. In subsequent years a decline in the radiation background rate occurred faster than reduction in the mutation rate. Plant and animal populations have shown signs of adaptation to chronic exposure. In adaptation to the enhanced level of exposure an essential role of epigenetic mechanisms of gene expression regulation was shown. Based on the Chernobyl NPP accident studies, in the present review attempts were made to assess minimum doses at which ecological and biological effects were observed.

Chernobyl radionuclide distribution, migration, and environmental and agricultural impacts

The distribution and migration of radionuclides released into the environment following the Chernobyl accident in 1986 are described. The Chernobyl disaster resulted in the consumption of farm products containing radionuclides as a source of irradiation of the population due to the prevalence of a rural type of human nutrition in the affected region. Economic and radiologic importance of countermeasures for reducing the impacts of the accident are described. The basic radioecological problem is described in which the area where direct radiation contamination of biota was observed is considerably smaller than the zone where concentrations of radionuclides through the food chain exceeded the permissible standards. The radiation-induced effects in biota in the affected area are described. In the long-term post-accident period, the radionuclide distribution between components of ecosystems (including humans) and doses are considered in comparison to a technologically normal situation of nuclear power plant operation. This analysis demonstrates that if radiation standards protect humans, then biota are also adequately protected against ionizing radiation.

Third annual Warren K. Sinclair keynote address: retrospective analysis of impacts of the Chernobyl accident

The accident at the Chernobyl Nuclear Power Plant in 1986 was the most severe in the history of the nuclear industry, causing a huge release of radionuclides over large areas of Europe. The recently completed Chernobyl Forum concluded that after a number of years, along with reduction of radiation levels and accumulation of humanitarian consequences, severe social and economic depression of the affected regions and associated psychological problems of the general public and the workers had become the most significant problem to be addressed by the authorities. The majority of the >600,000 emergency and recovery operation workers and five million residents of the contaminated areas in Belarus, Russia, and Ukraine received relatively minor radiation doses which are comparable with the natural background levels. An exception is a cohort of several hundred emergency workers who received high radiation doses and of whom 28 persons died in 1986 due to acute radiation sickness. Apart from the dramatic increase in thyroid cancer incidence among those exposed to radioiodine at a young age and some increase of leukemia in the most exposed workers, there is no clearly demonstrated increase in the somatic diseases due to radiation. There was, however, an increase in psychological problems among the affected population, compounded by the social disruption that followed the break-up of the Soviet Union. Despite the unprecedented scale of the Chernobyl accident, its consequences on the health of people are far less severe than those of the atomic bombings of the cities of Hiroshima and Nagasaki. Studying the consequences of the Chernobyl accident has made an invaluable scientific contribution to the development of nuclear safety, radioecology, radiation medicine and protection, and also the social sciences. The Chernobyl accident initiated the global nuclear and radiation safety regime.