The Chernobyl Nuclear Disaster Changed the DNA of Local Dogs
by Ed Cara / 3/6/23
“New research shines a light on how the Chernobyl disaster changed the DNA of the dogs that remained in the area. Scientists collected samples from hundreds of free-roaming canines in the exclusion zone and found that they were genetically distinct from dogs elsewhere in the world. The scientists are still exploring the potential long-term health effects from radiation exposure in these dogs, but what we learn might help us better prepare for similar accidents in the future, the researchers say. The 1986 Chernobyl disaster in the now-abandoned Ukrainian city of Pripyat is perhaps the most infamous nuclear accident of all time.
The initial explosion and subsequent fires at the plant scattered radioactive material into the surrounding environment. To this day, there remains a designated 1,000-square-mile area around the plant where elevated radiation is thought to be most hazardous to life, known as the Chernobyl Exclusion Zone. Several dozen people died during the accident and attempted clean-up, and it’s thought that at least thousands will or have died of cancer as a result of radiation exposure. The immediate impacts were also devastating for local wildlife. Nowadays, though, the area has become safe enough for humans to visit (at least for short periods) and some animal and plant populations have even bounced back stronger than they were before.
In 2017, scientists at the University of South Carolina and others began the Dogs of Chernobyl Research Initiative. They noticed that feral dog populations in and around the zone, some of which may have begun with pet dogs abandoned during the human evacuation, would surge in the summer then crash in the winter due to a lack of resources. Teaming up with veterinary and animal welfare clinics, they provided these dogs medical exams, vaccinations, and neutering/spaying if needed. But they also took the chance to study them up close, taking blood samples to analyze their DNA.
When they compared the genetics of the Chernobyl dogs to dogs from around the world, they found a clear distinction—enough to indicate these dogs and their descendants truly have been surviving in the zone since 1986 and that the experience has changed them on a deep level. But they also found differences among the exclusion zone dogs. The team’s findings are published this month in Science Advances.
“We find that there are two major populations of dogs within the Chernobyl Exclusion Zone; those that live in the industrial areas of the Chernobyl Nuclear Power Plant and those that live approximately 15 kilometers away in the residential area called Chernobyl City,” lead author Gabriella Spatola told Gizmodo. Spatola is a postdoctoral fellow at the Cancer Genetics and Comparative Genomics Branch, which studies dog genes as part of the National Human Genome Research Institute. Within these two large populations, Spatola and her team found, there were 15 families in total.
But they saw plenty of migration and intermixing as well, with the largest family having dogs found all across the sites they studied. They also have some purebred ancestry, particularly from shepherd-type breeds, Spatola said. Even today, we’re learning new things about how Chernobyl affected those living around it. And as far the authors know, this is the first genetics research of its kind that’s included larger nonhuman mammals like dogs.
They haven’t yet studied exactly how Chernobyl’s radiation changed these dogs and their lineage physically, but that’s next on the list. “The Chernobyl dog population provides a unique opportunity to study the long-term effects of radiation on a population that is closely linked to humans in a natural setting,” Spatola said. “Nuclear disasters will inevitably occur, and the information that we can gain from studying the impact this has on domestic populations will provide key insight into how we can be better prepared in the future.”
Some Chernobyl dogs were adopted
“Hundreds of the descendants of dogs abandoned by their owners during the site’s evacuation on April 27, 1986 have made the desolate area their home. Now, an organization called the Clean Future Fund helps conduct sterilization campaigns in the area. They also provide medical care, vaccinations, and even food to the Chernobyl pups (and cats). Back in 2018 and 2019, a number of dogs were identified as having safe levels of radiation, and a few dozen were actually adopted. As of mid-2022, it seemed that the combination of the pandemic and the Russian invasion of Ukraine have disrupted the organization’s efforts, though they do continue to do occasional work in the Exclusion Zone.
Some of the Chernobyl dogs have been adopted by people who live in the Exclusion Zone. Despite laws ostensibly prohibiting it, there are actually a number of human beings living in the Exclusion Zone, some with tacit permission from authorities. These residents are called Samosely, or self settlers. They’re mostly seniors, mostly women, and mostly lived in the area before the nuclear disaster. For any number of reasons, the Samosely have decided that the potential risks of radiation are outweighed by other considerations—financial, cultural, and geopolitical—that called them to the area.”
“In the early hours of 26 April 1986, two explosions rocked the nuclear power plant near the Ukrainian city of Chernobyl, then part of the Soviet Union. The accident at reactor four spewed radioactive material into the air, leading Soviet authorities to evacuate thousands of people from the surrounding area. Homes were left behind — and, in many cases, pets. In the days after the accident, response crews sought out abandoned and stray dogs, with the goal of killing them to stop the spread of radioactivity. Yet some seem to have survived.
In the first genetic study of any large mammal in the area around Chernobyl, DNA collected from feral dogs living near the power plant today reveals that they are the descendants of dogs that were either present at the time of the accident or that settled in the area shortly afterwards1. The study, published on 3 March in Science Advances, is the first step in a larger project aimed at determining how the dogs have adapted to survive in one of the most radioactive places on Earth.
Researchers hope to use the knowledge gained to better understand the effects of long-term radiation exposure on human genetics and health. “We have so much to learn from these animals,” says Elaine Ostrander, a geneticist at the US National Institutes of Health in Bethesda, Maryland, and co-author of the study. “This is a golden opportunity to see what happens when generations of large mammals live in a hostile environment.”
The immediate impacts of the accident at Chernobyl were obvious: around 30 people who worked at the power plant and fire fighters who attended after the disaster died of radiation poisoning within a few months of the catastrophe, according to the World Health Organization. And in the surrounding areas, pine trees withered and many insect species vanished, unable to survive in the radioactive soil. What is less clear is how low levels of lingering radioactive material from the disaster affect the plants and animals around Chernobyl today. A handful of studies have reported unusually high genetic mutation rates in barn swallows2 and fruit flies3 in the vicinity of the reactor, which is now entombed in a steel and concrete sarcophagus.
However, the health effects of low-levels of radiation are still hotly debated. This matters because people risk exposure to low doses of radiation in all sorts of contexts, including through certain medical scans or while working at nuclear power plants, says David Brenner, a radiation biophysicist at Columbia University in New York City who was not involved in the research. “It’s really difficult to figure out the effects” of this type of exposure, he adds, “but pretty important that we do so”. This was a motivating factor for co-author Timothy Mousseau, an evolutionary ecologist at the University of South Carolina in Columbia. In 2017, Mousseau joined a volunteer mission to provide veterinary care to the hundreds of stray dogs living in the exclusion zone, a 2,600-square-kilometre area around the power plant to which Ukrainian officials restrict access for safety reasons.
Over the course of three years of trips to the area, Mousseau and his colleagues collected blood samples from around 300 dogs living at the power plant and around the mostly deserted city of Chernobyl after volunteers had sedated the animals with tranquilizer darts. DNA analysis of the canines revealed that they were not newcomers to the area. By comparing the dogs’ genetic profiles to those of other free-roaming dogs in Eastern Europe, the team found that the canines in the vicinity of the power plant — some of which are related to shepherd breeds — have been isolated from other dog populations for decades.
And the researchers learnt that, despite Soviet concerns during the 1980s that the dogs would migrate and spread radioactive material, most of these animals hadn’t moved far: those living closest to the power plant are genetically distinct from their kin living just a few kilometres away. The dogs’ continued presence in the area shows that they were able to survive and breed, even while living near the reactor, “which is remarkable”, says Ostrander. The 1986 accident deposited the deadly radioactive isotope cesium-137 at levels 10 to 400 times higher near the power plant than in the city of Chernobyl, just 15 kilometres away. The canine DNA samples “are incredibly valuable” because dogs tend to share many of the same spaces and diets as humans, Ostrander says. “We’ve never had an opportunity to do this work in an animal that reflects us as well as dogs.”
But teasing out which genetic changes in the dogs are caused by radiation and which are caused by other factors — such as inbreeding or non-radioactive pollutants — won’t be easy, Brenner cautions. The team acknowledges these challenges, but the researchers argue that their detailed knowledge of these dogs’ ancestry, as well as knowledge of the levels of radiation different dogs were historically exposed to, “provides an ideal focus group for our future studies”. In the meantime, Mousseau is planning another sampling trip in June. The ongoing war in Ukraine hasn’t stopped the group’s research. But with fewer tourists visiting and leaving food scraps, Chernobyl’s dogs are struggling to get by. So the team is working with a non-governmental organization to provide food to the strays, safeguarding the survival of Chernobyl’s dogs — and their radioactive legacy — in the lean times ahead.”
Spatola, G. J. et al. Sci. Adv. 9, eade2537 (2023) Article
Ellegren, H., Lindgren, G., Primmer, C. & Møller, A. P. Nature 389, 593–596 (1997) Article PubMed
Hancock, S. et al. Environ. Res. 172, 333–337 (2019) Article PubMed
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