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 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.