Dose reconstruction supports the interpretation of decreased abundance of mammals in the Chernobyl Exclusion Zone

Radiation dose reconstruction for higher aquatic plants and fish in Glyboke Lake during the early phase of the Chernobyl accident

This study deals with an assessment of radiation dose dynamics to fish and higher aquatic plants (helophytes) in Glyboke Lake (10-km exclusion zone) during the early phase of the Chernobyl accident. Models of radioactive contamination of water and sediment and models of radioactive contamination and radiation dose to fish and aquatic plants were developed. It was found that, in 1986, the total dose rate to fish reached 0.25 Gy d^-1. Within 6 months after the accident, the dose rate due to ⁹⁰Sr, ¹³⁴Cs and ¹³⁷Cs had increased. The absorbed dose to prey fish of Glyboke Lake for this period was estimated as being 27-81 Gy of which 4-40 Gy was formed by ¹³¹I exposure. The radiation dose rate due to ⁹⁰Sr, ¹⁰⁶Ru, ^134+137Cs and ¹⁴⁴Ce to aquatic plants reached its quasi-equilibrium values approximately 50 days after the accident and remained virtually unchanged until the end of the 1986 growing season. The highest levels of ⁸⁹Sr, ⁹¹Y, ⁹⁵Zr, ¹⁰³Ru, ¹⁴¹Ce exposure were observed between 30 and 50 days with a decrease by 2-3 times at the end of the growing season. Radiation exposure of the short-lived ¹³¹I, ¹⁴⁰Ba, ¹⁴⁰La, ²³⁹Np reached its maximum within 5-15 days after the accident. The absorbed dose rate to aquatic plants reached 0.69 Gy d^-1, while the contribution of cerium radionuclides to the total dose rate formed 50% in the initial period and reached 90% at the end of the growing season. The magnitude of the radiation dose rate to plant roots was 2.4 times higher than aboveground organs, and that of rhizomes was 1.6 times higher. During the growing season of 1986 the total dose of exposure of plants in Glyboke Lake was about 78 Gy. The results of this study emphasise the necessity to consider the history of exposure of past generation of living organisms as part of the assessment of current radiation effects.

Impact of ionizing radiation on the environmental microbiomes of Chornobyl wetlands

Radioactive contamination has the potential to cause damage to DNA and other biomolecules. Anthropogenic sources of radioactive contamination include accidents in nuclear power plants, such as the one in Chornobyl in 1986 which caused long-term radioactive pollution. Studies on animals within radioactive zones have provided us with a greater understanding of how wildlife can persevere despite chronic radiation exposure. However, we still know very little about the effects of radiation on the microbial communities in the environment. We examined the impact of ionizing radiation and other environmental factors on the diversity and composition of environmental microbiomes in the wetlands of Chornobyl. We combined detailed field sampling along a gradient of radiation together with 16 S rRNA high-throughput metabarcoding. While radiation did not affect the alpha diversity of the microbiomes in sediment, soil, or water, it had a significant effect on the beta diversity in all environment types, indicating that the microbial composition was affected by ionizing radiation. Specifically, we detected several microbial taxa that were more abundant in areas with high radiation levels within the Chornobyl Exclusion Zone, including bacteria and archaea known to be radioresistant. Our results reveal the existence of rich and diverse microbiomes in Chornobyl wetlands, with multiple taxonomic groups that are able to thrive despite the radioactive contamination. These results, together with additional field and laboratory-based approaches examining how microbes cope with ionizing radiation will help to forecast the functionality and re-naturalization dynamics of radiocontaminated environments.

Population dynamics and genome-wide selection scan for dogs in Chernobyl

BACKGROUND

Natural and anthropogenic disasters can have long-lasting impacts on the genetics and structure of impacted populations. The 1986 Chernobyl Nuclear Power Plant disaster led to extensive contamination of the local environment and the wildlife therein. Several ecological, environmental, and genetic studies reported various effects of this disaster on animal, insect, and plant species; however, little work has been done to investigate the genetics of the free-breeding dogs that occupy the Chernobyl Exclusion Zone (CEZ).

RESULTS

We define the population genetic structure of two groups of dogs that reside within the CEZ, one around the reactor site itself and another living within Chernobyl City. We found little evidence of gene flow and a significant degree of genetic differentiation between the two populations dogs, suggesting that these are two distinct populations despite occupying areas located just 16 km apart. With an F_ST-based outlier analysis, we then performed a genome-wide scan for evidence of directional selection within the dog populations. We found 391 outlier loci associated with genomic regions influenced by directional selection, from which we identified 52 candidate genes.

CONCLUSIONS

Our genome scan highlighted outlier loci within or near genomic regions under directional selection, possibly in response to the multi-generational exposure faced. In defining the population structure and identifying candidate genes for these dog populations, we take steps towards understanding how these types of prolonged exposures have impacted these populations.

The dogs of Chernobyl: Demographic insights into populations inhabiting the nuclear exclusion zone

The 1986 Chernobyl nuclear disaster initiated a series of catastrophic events resulting in long-term and widespread environmental contamination. We characterize the genetic structure of 302 dogs representing three free-roaming dog populations living within the power plant itself, as well as those 15 to 45 kilometers from the disaster site. Genome-wide profiles from Chernobyl, purebred and free-breeding dogs, worldwide reveal that the individuals from the power plant and Chernobyl City are genetically distinct, with the former displaying increased intrapopulation genetic similarity and differentiation. Analysis of shared ancestral genome segments highlights differences in the extent and timing of western breed introgression. Kinship analysis reveals 15 families, with the largest spanning all collection sites within the radioactive exclusion zone, reflecting migration of dogs between the power plant and Chernobyl City. This study presents the first characterization of a domestic species in Chernobyl, establishing their importance for genetic studies into the effects of exposure to long-term, low-dose ionizing radiation.

The Biology of Chernobyl

Environmental disasters offer the unique opportunity for landscape-scale ecological and evolutionary studies that are not possible in the laboratory or small experimental plots. The nuclear accident at Chernobyl (1986) allows for rigorous analyses of radiation effects on individuals and populations at an ecosystem scale. Here, the current state of knowledge related to populations within the Chernobyl region of Ukraine and Belarus following the largest civil nuclear accident in history is reviewed. There is now a significant literature that provides contrasting and occasionally conflicting views of the state of animals and how they are affected by this mutagenic stressor. Studies of genetic and physiological effects have largely suggested significant injuries to individuals inhabiting the more radioactive areas of the Chernobyl region. Most population censuses for most species suggest that abundances are reduced in the more radioactive areas.

Individual quality and phenology mediate the effect of radioactive contamination on body temperature in Chernobyl barn swallows

Anthropogenic stressors, such as radioactive contaminants released from the Chernobyl and Fukushima Daiichi accidents, deteriorate ecological and evolutionary processes, as evidence for damaging effects of radioactive contamination on wildlife is accumulating. Yet little is known about physiological traits of animals inhabiting contaminated areas, and how those are affected by individual quality and phenology. We investigated variation in body temperature of wild barn swallows, Hirundo rustica, exposed to radioactive contamination from the Chernobyl accident in Ukraine and Belarus. We tested whether exposure to variable levels of radioactive contamination modified core body temperature of birds, and whether individual and phenological characteristics modulated radiosensitivity of body temperature. We showed that barn swallow body temperature varied with exposure to environmental radioactive contamination and that individual characteristics and phenology affected radioactive exposure. Increased radiosensitivity and up-regulation of body temperature were detected in birds of low body condition, high risk of capture, and in animals captured late during the day but early during the season. These results highlight the complex ways that the body temperature of a wild bird is impacted by exposure to increased radioactive contamination in natural habitats. By impacting body temperature, increased radioactive contamination may compromise energetic balance, jeopardize responsiveness to global warming, and increase risk of overheating.

Disproportionate Impacts of Radiation Exposure on Women, Children, and Pregnancy: Taking Back our Narrative

Narratives surrounding ionizing radiation have often minimized radioactivity's impact on the health of human and non-human animals and the natural environment. Many Cold War research policies, practices, and interpretations drove nuclear technology forward by institutionally obscuring empirical evidence of radiation's disproportionate and low-dose harm-a legacy we still confront. Women, children, and pregnancy development are particularly sensitive to exposure from radioactivity, suffering more damage per dose than adult males, even down to small doses, making low doses a cornerstone of concern. Evidence of compounding generational damage could indicate increased sensitivity through heritable impact. This essay examines the existing empirical evidence demonstrating these sensitivities, and how research institutions and regulatory authorities have devalued them, willingly sacrificing health in the service of maintaining and expanding nuclear technology (Nadesan 2019). Radiation's disproportionate impacts should now be the research and policy focus, as society is poised to make crucial and long-lasting decisions regarding climate change mitigation and future energy sources (Brown 2019b).

Radiocesium concentration ratios and radiation dose to wild rodents in Fukushima Prefecture

Radiocesium was dispersed from the Fukushima Dai-ichi disaster in March 2011, causing comparatively high radioactive contamination in nearby environments. Radionuclide concentrations in wild rodents (Apodemus argenteus, and Apodemus speciosus) within these areas were monitored from 2012 to 2016. However, whole-organism to soil transfer parameters (i.e., concentration ratio, CR_wo-soil) for wild rodents at Fukushima were not determined and hence were lacking from the international transfer databases. We augmented the 2012-2016 data by collecting soil activity concentrations (Bq kg^-1, dry mass) from five rodent sampling sites in Fukushima Prefecture, and developed corresponding CR_wo-soil values for radiocesium (¹³⁴Cs and ¹³⁷Cs) based on rodent radioactivity concentrations (Bq kg^-1, fresh mass). The CR_wo-soil were added to the Wildlife Transfer Database (WTD; http://www.wildlifetransferdatabase.org/), supporting the development of the International Commission on Radiological Protection's (ICRP) environmental protection framework, and increasing the WTD from 84 to 477 entries for cesium and Muridae ('Reference Rat'). Significant variation occurred in CR_wo-soil values between study sites within Fukushima Prefecture. The geometric mean CR_wo-soil, in this paper, was higher than that reported for Muridae species for Chernobyl. Radiocaesium absorbed dose rates were also estimated for wild rodents inhabiting the five Fukushima study sites and ranged from 1.3 to 33 μGy h^-1. Absorbed dose rates decreased by a factor of two from 2012 to 2016. Dose rates in highly contaminated areas were within the ICRP derived consideration reference level for Reference Rat (0.1-1 mGy d^-1), suggesting the possible occurrence of deleterious effects and need for radiological effect studies in the Fukushima area.