In 2018, scientists collected blood samples from eight dogs in Ukraine's Chernobyl Exclusion Zone – four from the Chernobyl Nuclear Power Plant (ChNPP) and four from Chornobyl city.
The two dog populations, while only 10 miles apart, are genetically distinct and the researchers wanted to find out whether radiation-induced mutation is contributing to these differences.
The findings, made by researchers from North Carolina State University and Columbia University Mailman School of Public Health, were published in the journal PLOS ONE and shed light on how environmental contamination can impact animal populations over time.
A deep dive
"We have been working with two dog populations that, while separated by just 16 kilometres, or about 10 miles, are genetically distinct,” explains Matthew Breen, Oscar J. Fletcher Distinguished Professor of Comparative Oncology Genetics at NC State.
"We are trying to determine if low-level exposure over many years to environmental toxins such as radiation, lead, etcetera, could explain some of those differences."
In earlier research, the team analysed genetic variants across the dogs' genomes and identified 391 regions that stood out between the two populations. Some of these regions contained genes linked to repairing DNA damage.
The latest study took this analysis further, delving deeper into the dogs' genomes to search for signs of mutations that might have built up over time.
"Most people think of the Chornobyl nuclear accident as a radiological disaster in an abandoned corner of Ukraine, but the potential adverse health implications are much wider,” says Norman Kleiman, senior co-author and professor of environmental health sciences at Columbia University School of Public Health.
"This is due to the many other toxins – including heavy metals, lead powder, pesticides, and asbestos – released into the environment during the ensuing cleanup and remediation over three decades."
What they did
The researchers started by comparing the genetic differences between the two dog populations. They found that the genetics of the Chornobyl city dogs were similar to those of dogs in Russia, Poland and nearby areas. “That way, we were able to use the Chornobyl City dogs as a representative control population to compare with the ChNPP dogs,” says Megan Dillon, PhD candidate at NC State and lead author of the study.
The team then examined the dogs' genomes more closely, from entire chromosomes down to individual nucleotides, searching for abnormalities or accumulated DNA mutations. These 'germline' mutations, which occur in reproductive cells, can be passed down through generations, the authors explain.
"Think of it like using the zoom function on your phone’s camera to get more details – we start with a wide view of a subject and then zoom in,” says corresponding author Breen.
"We know that, for example, exposure to high doses of radiation can introduce instability from the chromosomal level on down. While this dog population is 30 or more generations removed from the one present during the 1986 disaster, mutations would likely still be detectable if they conferred a survival advantage to those original dogs. But we didn’t find any such evidence in these dogs.”
What they found
The researchers say that the analysis didn’t uncover evidence of radiation-induced genetic mutations. But they add that this doesn’t rule out the influence of selective pressures in shaping the two dog populations.
"In human terms, this would be like studying a population that is centuries removed from the one present at the time of the disaster,” explains Dillon.
"It’s possible that the dogs that survived long enough to breed already had genetic traits that increased their ability to survive. So perhaps there was extreme selective pressure at the start, and then the dogs at the power plant just remained separate from the city population. Investigating that question is an important next step that we are now working on.”
The authors suggest that the study provides a broader understanding of how environmental hazards impact both animal and human health.
"While no one lives at the ChNPP or in Pripyat anymore, up until the Russian invasion many thousands of people continued to work there every day on remediation and construction projects nearby,” Kleiman says.
"Studying companion animals like these dogs offers a window into the kinds of adverse health risks that people may face.”
The team highlights the importance of continuing to study the environmental health impacts of large-scale disasters like this "as it is certain, given our increasingly technological and industrial societies, there will invariably be other such disasters in the future, and we need to understand the potential health risks and how best to protect people,” concludes Kleiman.
Find out more about the study: Is increased mutation driving genetic diversity in dogs within the Chornobyl exclusion zone?
Main image: wild dog (not involved in study) in old radioactive zone in Pripyat city/Getty
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