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Chernobyl's Stray Dogs Are Genetically Distinct—But Radiation Isn't The Reason
In 1986, the Chernobyl nuclear reactor in the Soviet Union, now in Ukraine, exploded, spewing massive amounts of radioactive material into the environment. Almost four decades later, the stray dogs that roam near the Chernobyl Nuclear Power Plant are genetically different from the ones in the nearby city of Chernobyl—but it's probably not because of the radiation.
Researchers from North Carolina State (NC State) University and Columbia University Mailman School of Public Health have concluded that the genetic differences between dogs in Chernobyl City and the ones near the Chernobyl Nuclear Power Plant (NPP) were likely not driven by radiation-induced mutations. Their research, detailed in a December 27 study published in the journal PLOS One, provides insight on how disastrous environmental contamination affects nearby populations over time.
"We have been working with two dog populations that, while separated by just 16 kilometers, or about 10 miles, are genetically distinct," said Matthew Breen of NC State, who participated in the study, in a university statement. "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 previous genetic analyses, Breen and his colleagues had identified almost 400 regions along the genome that represented differences between the two canine populations, with some containing genes associated with the repair of DNA damage.
In the recent study, the team confirmed that the city dogs were genetically similar to dogs in nearby regions like Russia and Poland, establishing them as the representative control population to which they could compare the NPP group. They then searched for abnormalities and mutations in the NPP dogs that could have accumulated over time. Germline DNA mutations, for example, are inheritable changes within the DNA of reproductive cells. The researchers began their analysis at the chromosomal level, and then progressively zoomed in to smaller and smaller genetic features.
"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," Breen explained. "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."
In other words, the researchers didn't find genetic mutations that could have been caused by exposure to radiation. Evolutionary pressures caused by the nuclear reactor disaster, however, could have still driven the genetic difference between the city dogs and the NPP dogs.
"In human terms, this would be like studying a population that is centuries removed from the one present at the time of the disaster," said Megan Dillon of NC State, who led the study. "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 adverse effects of the Chernobyl nuclear accident, in fact, weren't just limited to radiation, said Kleiman of Columbia University, who was also involved in the study. Toxins including heavy metals, lead powder, pesticides, and asbestos (a carcinogenic mineral) were released into the environment during the cleanup process. The broader impact of the nuclear disaster on nearby dog populations provides important clues for how future contamination crises could influence human health.
The Terrifying Reasons We're Confronting the Chernobyl Disaster Right Now
"The importance of continuing to study the environmental health aspects of large-scale disasters like this cannot be overemphasized," Kleiman said, "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."
It's also a relief to know that the pups roaming near the Chernobyl Nuclear Power Plant have nothing to do with the wild dogs from Chernobyl Diaries.
Chernobyl's Feral Dogs Are Genetically Unique, But Not Mutated
Feral dogs living near Chernobyl differ genetically from their ancestors who survived the 1986 nuclear plant disaster—but these variations do not appear to stem from radioactivity-induced mutations. The new findings are helping experts contextualize how such ecological catastrophes influence the environment around them, and how these effects ripple out over time.
Chernobyl's reactor meltdown remains history's worst nuclear disaster. The initial explosion killed two facility workers on April 26, 1986, but at least another 28 people succumbed to acute radiation poisoning and associated issues over the next three months. At least 9,000 cancer-related fatalities across Ukraine, Belarus, and Russia occurred in the decades since the meltdown, and a roughly 1,000-square-mile exclusion zone still exists around the facility that includes the abandoned town of Pripyat. In addition to the confirmed deaths, other longterm effects suggested by multiple studies include contaminated water, damage to plantlife, and birth defects in both humans and animals.
The ecological damage remains difficult to comprehend, but the region never became completely devoid of life. Many animals survived even after undergoing radiation-based genetic mutations—notably, a number of pet dogs abandoned by their owners during Chernobyl's hasty evacuation orders. Today, several hundred feral dogs are estimated to live in the area, presenting a unique opportunity to study how these populations adapt to immense and sudden environmental degradation.
[ Related: Without humans, what would happen to life on Earth? ]
In a study published last year, researchers identified stark genetic differences between the Exclusion Zone's feral dogs and dogs living barely 10 miles away in Chernobyl City. These included 391 genetic outlier regions between the two populations, some specifically associated with DNA repair. But according to their follow-up investigation published in the journal PLOS One, the team now says there is "no evidence" that these contrasts are the result of an increased mutation rate.
The researchers reached their conclusion after analyzing samples at the chromosomal level, followed by small genome intervals and differences between individual nucleotides. They were particularly on the hunt for evidence of abnormalities such as accumulated germ line DNA mutations—alterations in reproductive cell DNA passed from parents to offspring over multiple generations. Matthew Breen, an NC State professor of comparative oncology genetics and study corresponding author, likened the overall process to using your phone camera's zoom function.
"[W]e start with a wide view of a subject and then zoom in," Breen said in an accompanying statement on January 13th. "We know that, for example, exposure to high doses of radiation can introduce instability from the chromosomal level on down."
Breen noted that while the current dog population is more than 30 generations removed from the Chernobyl disaster in 1986, the team would likely still identify genetic mutations if, for example, they provided some form of survival advantage. Researchers, however, found no evidence of such abnormalities.
"[M]utation does not appear to be the cause of the previously identified genetic differentiation between these two geographically close populations of free-breeding dogs," the study authors conclude. "Considering this, in conjunction with the previous work on breed composition, inbreeding, and comparisons to other free-breeding dog populations, we have yet to identify the definitive cause for this genetic differentiation."
Megan Dillon, an NC State PhD candidate and study lead author, believes the first generation of dogs who survived Chernobyl may have done so thanks to certain genetic traits they already possessed—not those conferred through radioactive mutation.
"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," she said. "Investigating that question is an important next step that we are now working on."
Their latest findings extend far beyond dogs, as well. Given the number of canine generations that have lived since the nuclear meltdown, Dillon likened the present-day population to humans "centuries removed from the [those] present at the time of the disaster."
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But just because today's Chernobyl dogs lack genetic mutations from radioactive fallout doesn't mean they—or the people still working on cleanup efforts—are safe from health issues.
"Most people think of the Chernobyl nuclear accident as a radiological disaster in an abandoned corner of Ukraine, but the potential adverse health implications are much wider," added Norman Kleiman, study co-author and a professor of environmental health sciences at Columbia University School of Public Health.
Kleiman explained that, in addition to radiation, other toxins such as lead powder, pesticides, asbestos, and heavy metals have been released into the environment over three decades of remediation work undertaken by thousands of people.
"The importance of continuing to study the environmental health aspects of large-scale disasters like this cannot be overemphasized," said Kleiman.
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Cousins Ruby da Cherry and $crim, of Suicideboys, from New Orleans, perform on the Bridge stage during the first day of the 2022 BUKU Music + Art Project in New Orleans, Friday, March 25, 2022. BUKU is the first major festival in New Orleans since the start of the coronavirus pandemic. (Photo by Sophia Germer, NOLA.Com, The Times-PicayuneThe New Orleans Advocate)
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