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Reactions: study shows dogs living near Chernobyl are genetically unique

A study has analyzed the genetics of 302 dogs living in areas close to the Chernobyl nuclear power plant. According to the study, they show genetic differences according to the distance they live from the plant, which distinguish them from other dog populations. The results are published in the journal Science Advances.

03/03/2023 - 20:00 CET
Chernobyl Dogs

Chernobyl dogs live in a variety of habitats throughout the nuclear exclusion zone including forested areas around Pripyat and Chernobyl City / Jordan Lapier

Expert reactions

Chernóbil - Orizaola

Science Media Centre Spain

This is a descriptive study of the population structure of feral dogs in the Chernobyl Exclusion Zone. The study is interesting to learn about the population dynamics of Chernobyl dogs, but since its design does not include any estimation of radiation exposure or other environmental factors, it is not possible to estimate from this work any effect of radiation exposure on any of the parameters studied. The article has very little to do with the press release with which they want to promote it [in the press release the genetic changes are attributed to exposure to different doses of radiation]. 

The study must be understood as a study of population dynamics in small feral populations, fundamentally disconnected from other similar populations due to the scarce presence of humans (and therefore dogs) around them. A large part of the results presented can be explained by the fact that the Chernobyl dog population is a population that originates from a rather small number of individuals and because it is still quite isolated from similar populations. 

The study presents good quality in its genetic analyses, but since it does not include any data reflecting radiation exposure in the individuals studied, its conclusions cannot go beyond the analysis of the dynamics of a feral vertebrate population. It would be the equivalent of studying the structure and interconnectedness of stray cat populations in Madrid. 

It brings the novelty of studying the interconnection between the different groups of dogs in the area, which could provide information for their possible management. By not studying in any way any parameters in relation to the levels of radiation that these dogs may have experienced throughout their lives, it is not possible to conclude anything about the possible changes that may have occurred as a result of exposure to radiation. 

It is important to note that the study was conducted between 2017 and 2019, when radiation levels in the Area have been reduced by more than 90% since the time of the accident, and the isotopes most harmful to living organisms, such as I-131 have been gone for decades. 

To put the study in perspective, one of the large groups of dogs studied, that of the city of Chernobyl, is currently in an environment with radiation levels equivalent to those that can be found naturally in the Iberian Peninsula. Today all the measuring stations in the city of Chernobyl register less than 0.25 microSv/h, values that are found naturally in large areas of the central and northwestern part of the Peninsula. 

From my point of view there are many limitations to consider the study as relevant from the point of view of the effects of radioactive contamination on living organisms. The main one, that radiation exposure is not measured in any of the individuals studied, and therefore makes the study uninteresting, as such, from a radiological point of view.   

A worrying aspect is the fact that the authors do not seem to distinguish between the initial effects of the accident and the current situation, more than three decades later with a radical change in radiation levels and the identity of the radioactive substances. The article insists that the accident generated "an ecological catastrophe of massive proportions" and "that many species have not recovered from the consequences of the catastrophe" (without providing data to support these assertions), ignoring the works that indicate that at present the Chernobyl Exclusion Zone is one of the largest natural reserves in Europe, an example of passive renaturation processes, and with clear and abundant examples of species with notable population increases.

The author has not responded to our request to declare conflicts of interest

Chernóbil - James

James Smith

Professor of environmental sciences at the University of Portsmouth (UK).

Science Media Centre Spain

This study analyses the population structure of dogs at Chernobyl, finding that dogs at Chernobyl had different population structures to two other free-living dog populations. It is important to note, however, that this study in no way links differences in population structure of dogs to current radiation at Chernobyl. It only shows that there is a different mix of breeds and families at Chernobyl compared to the other sites - this isn't a surprising finding given that the current population depends on the particular mix of breeds which survived the domestic animal cull in 1986 as well as subsequent introductions.

The context of this work is poorly explained, in my opinion. For example, the authors claim that ‘the abundance of wildlife populations within the CEZ was significantly reduced following the accident’ - citing the findings of a small study which in my opinion has significant statistical flaws (Moller and Mousseau, 2013; Beaugelin-Seiller et al. 2020) and which has been contradicted by much more robust studies (Deryabina et al. 2015; Webster et al. 2016; Beresford et al. 2023). I think that the paper could mislead the reader, claiming ‘although some species appear to have recovered, likely due to a lack of human disturbance, many have not’ - citing a paper I led when in fact our paper in no way supports the authors' claim that many have not recovered.

I am surprised that the authors do not clearly state in the paper that their results do not show that radiation is causally linked to differences in population structure of dogs at Chernobyl. I am also surprised that the title of the press release claims ‘The dogs of Chernobyl may be genetically distinct due to varying levels of radiation exposure’ when the paper presents no evidence to support a causal relationship between population structure and radiation dose.

That is not to say that extremely high radiation doses in some areas during the first weeks after the accident couldn't have impacted significantly on domestic and wild animal populations. Nor does a lack of evidence in this paper show that there is no effect of radiation on animals at Chernobyl.

The author has not responded to our request to declare conflicts of interest

Stephen Chanock - Chernóbil EN

Stephen Chanock

Director of Cancer Epidemiology and Genetics, National Cancer Institute, USA

Science Media Centre Spain

This is superb study of the changes in the genetics of the populations of dogs in and around the Chernobyl site. The authors have carefully evaluated how the shifts in relatedness have changed under the pressure of a restricted environment, here driven by the zones established to contain animals roaming regions contaminated with radiation that persists after deposition following the accident of 1986.

This study is a first step towards evaluating how and in what way exposure to environmental ionizing radiation (here CS-137) could affect subsequent generations- which was not reported- nor evaluated- in this study of common variants shared amongst dogs. It is an important and rigorous study that sets the stage for studying whether continual exposure to radiation could scar the genome, a pressing question for animals and humans.

This study is well conducted and provides fascinating details about populations of dogs under strong pressures. [However] the study design does not enable the exploration of actual changes in the genome due to extensive radiation exposure. One expects the next study will likely address this- and it is important to pursue this in the very population studied here to further understand how a steady exposure to environmental ionizing radiation affects the genome.

The author has not responded to our request to declare conflicts of interest
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