Dr. Betz

Dogs of Chernobyl photo

Since 2017, Dr. Jennifer Betz has been treating and studying the hundreds of stray dogs that live at or near the Chornobyl nuclear power plant.

When a reactor exploded at the Chornobyl nuclear power plant, the thousands of people evacuated from a 19-mile exclusion zone were ordered to leave their pets behind. Soviet authorities said they'd be home in around three days. That never happened, and their dogs, cats and any other animals were abandoned in the wake of what turned out to be, and still is, the worst nuclear accident in history.

Today, nearly 40 years later, the descendants of some of those abandoned animals live on, including hundreds of stray dogs that inhabit the dilapidated remnants of the plant and nearby town of Chornobyl, both located in what is now northern Ukraine.

Their perseverance has created animal welfare and public health problems. The dogs are malnourished and susceptible to rabies, posing safety threats to workers involved in the ongoing decommissioning of the still-radioactive plant. More positively, the dogs are providing veterinarians and other scientists with an opportunity to study, among other things, how long-term radiation exposure affects animals, and how much of a contamination risk those animals present to humans.

Dr. Jennifer Betz, a veterinarian in Oregon, has been sterilizing, feeding, treating and studying the strays since 2017 as the veterinary medical director of Dogs of Chernobyl, an initiative founded by the nonprofit Clean Futures Fund. (The organization uses the Russian spelling for the location; Chornobyl is the Ukrainian spelling.) Betz visits the region three to four times a year, even in the midst of the Russia-Ukraine war, now in its fourth year, and has just returned from her latest trip. Because of a no-fly zone, she catches a train from Poland to the Ukraine capital, Kyiv, and drives to Chornobyl through numerous checkpoints.

"Chornobyl is right on the Belarusian border, so all night long there's Shahed drones flying overhead," she said, referring to the Iranian-made kamikaze drones deployed by Russian forces. "People ask, 'Aren't you scared to go?' But to me, Kyiv is a lot more dangerous, as it's being struck every single night."

Continuing to travel to Ukraine is worth the effort, Betz believes, in part because the dogs of Chornobyl make such compelling research subjects.

In a groundbreaking discovery published in 2023 and coauthored by Betz, dogs that live on the power plant's grounds or in the city of Chornobyl, around 10 miles away, were found to have a unique genomic signature. That indicates that very few new dogs have migrated into those areas since the accident occurred in 1986, meaning most of the dogs are descendants of the originally abandoned pets. The dogs that live on the power plant grounds have an especially pure lineage.

"It's a closed population," Betz said. "So researchers can see if radiation exposure has caused any damage to the DNA and determine if there are any long-term effects of low-dose ionizing radiation."

Radiation is energy that moves from one place to another as waves or particles. Ionizing radiation is strong enough to displace electrons from atoms and can hurt organisms by damaging their cells and DNA.

The isolated nature of the dog population also has given Betz an unprecedented opportunity to observe the effectiveness of dog sterilization campaigns.

"Even in the Galápagos Islands, where we did a research paper on sterilization, we discovered that new dogs were still coming in, so if you didn't keep spaying and neutering every five years, you'd have the same numbers back again," she said. "Whereas in Chornobyl, even though we've almost stopped sterilizing, dog numbers are still going down."

Thanks to desexing, Betz estimates there are now fewer than 300 dogs in the Chornobyl exclusion zone, down from around 1,000 when she first visited in 2017.

Dogs got off relatively lightly

Immediate adverse effects of radiation poisoning include skin burns and acute radiation syndrome, a severe and potentially fatal illness characterized by dizziness, vomiting, hair loss, bleeding and organ damage. Long-term effects can include cancer, cardiovascular disease and, in exposed pregnant individuals, birth defects.

The risk of harm from radiation poisoning is most acute in the immediate aftermath of a disaster, but some radioactive material can linger in the environment for periods ranging from decades to millennia, depending on the element. The main two that persist in the Chornobyl exclusion zone are cesium and strontium; more specifically, the radioactive isotopes cesium-137 and strontium-90. (Isotopes are atoms of the same element that differ in mass due to a differing number of neutrons.) Cesium-137 and strontium-90 both have half-lives of around 30 years, meaning it takes that long for half of the radioactive atoms in a sample to decay.

The extent to which animals at Chornobyl are still harmed by those elements is the subject of ongoing studies by the Dogs of Chernobyl program, the National Institutes of Health — an agency of the United States government — and scientists at the University of South Carolina.

Signs of poisoning are most noticeable in wildlife, according to Timothy Mousseau, a University of South Carolina biologist with expertise in how radiation affects animals.

"We've documented smaller brain size in birds and rodents living in the area, but for most of those animals, they've definitely had much higher doses of radiation than what the dogs have experienced," he said.

The dogs are safer, he explained, because they tend to subsist on uncontaminated food provided by humans, be they power plant workers or, more recently, members of the Dogs of Chernobyl program.

"They don't really have to forage. And domestic dogs are not great foragers to begin with," he said. "They're maybe going to pick up some exposure if they're hunting rabbits or squirrels. They might eat a little bit of the vegetation every now and then, the way dogs do, but that's a trivial input."

Mousseau said the dogs are more exposed through radioactive dust when they dig holes or roll around in the dirt. "That'll get on their skin and in their fur, but that's going to wash off pretty quickly, within a few weeks," he said.

Some places are more contaminated than others: Radiation is spread unequally around the Chornobyl exclusion zone in what Mousseau describes as a mosaic.

Researchers including veterinarians also are studying the dogs for clues on how long-term exposure to radiation affects animals and their offspring. To date, there's little definitive evidence of radiation poisoning in the dogs. Some have developed cancer or asymmetries in leg length or head shape, but these signs could be the result of inbreeding.

For her part, Betz has seen a few cancers, though it's often a type of bone cancer seen in large breed dogs as they age. "Is it because they're an old large breed dog, or is it because of radiation? We don't know," she said.

Studying the animals is tough, she adds, because many are shy and hard to catch, and the researchers visit only intermittently. "Often, we're just maintaining them to make sure they're healthy and happy, and if they're suffering, we will euthanize them if necessary," she said.

One clear sign of radiation exposure in birds and mammals that's distinctly associated with radiation poisoning is cataracts, a condition in which the lenses of the eyes become opaque. (Mousseau himself has developed cataracts, due to, he suspects, the time he's spent at Chornobyl and in the exclusion zone around the nuclear power plant in Fukushima, Japan, the site of a major accident in 2011.) But to date, there is little evidence that the dogs have developed the condition, he said.

Another chief aim of the studies is to determine whether radiation damage to DNA can be passed on through multiple generations — a contentious topic in scientific circles. Research published in 2021 conducted by the NIH's National Cancer Institute found that humans exposed to radiation from the Chornobyl accident didn't pass genetic damage to their children. That echoed findings of studies on the offspring of people exposed to the atomic bombs dropped on Hiroshima and Nagasaki in 1946.

Still, transgenerational damage to DNA from radiation exposure has been identified in other animals, such as fruit flies, mice and worms.

As for the dogs at Chornobyl, preliminary research results are mixed.

One study, led by Mousseau and colleagues at the University of South Carolina and published last December, found no evidence of increased rates of genetic mutation among the dogs. However, Mousseau noted, the number of dogs studied was small, fewer than 100.

"We have another paper in preparation from the NIH group that digs into that question in much more detail," Mousseau said. "And we found some genes were turned on, and some genes were turned off related to DNA repair. That, again, was not from a huge sample size, so not conclusive, but certainly is suggestive that there were consequences of the radiation exposure at the genetic level."

Are 'radioactive' pets safe to adopt?

Betz doesn't see the dogs of Chornobyl as presenting a particularly high radiation contamination risk to humans, in part because any cesium or strontium on their body surfaces is removable. "You can wash it off. You can clip the fur and be fine," she said.

Still, strontium acts like calcium and can therefore be absorbed into animals' bones. "We have found several animals where, no matter what you did, we couldn't remove the radiation, as it was all within their skull — most likely strontium-90," Betz said.

Mousseau points out that for a person to be contaminated by such bone-embedded radiation, they'd have to eat the bones.

Cesium can contaminate other internal organs but tends to dissipate relatively quickly. "It will be diluted and released into the environment through its urine, through its poop," Mousseau said. "Radioactive cesium has a biological half-life of probably one to three months in your typical dog, so it'll gradually completely disappear."

Pups

Dogs of Chernobyl photo

After being sterilized and microchipped, dogs are given temporary markings to easily distinguish them from those that haven't yet been captured for desexing.

A total of 34 dogs have been adopted out from the Chornobyl exclusion zone, all of them puppies from two groups found without their mothers. Ukrainian authorities prohibit taking anything from the zone but made an exception in 2018 for the newborn puppies, which had to be quarantined for four months and tested regularly before being rehomed. "It was incredibly costly," Betz said. "They're all doing well and we still follow them, but it's not something we'd ever do again — or that the authorities will allow again."

A paper published this month in the Journal of Environmental Radioactivity supports the notion that the dogs — and dozens of cats — living in the Chornobyl exclusion zone pose limited contamination risks to humans. The study based its conclusion on modeling only, taking likely radiation exposures in the Chornobyl and Fukushima exclusion zones and applying them to hypothetical pet owners.

An evaluation of "various pet-owner bonding scenarios" showed doses were "negligible" and not expected to be a serious concern, the paper states. "Bonding with radioactive pets may offer health benefits outweighing low-dose risks," it concludes.

Still, Mousseau notes risk will vary depending on the severity of the disaster and how much time has elapsed since the incident. "Initially, right after the Chornobyl event, the animals and people and everything else — the cars, the buses, the tractors — were all incredibly radioactive," he said.

Some of the same researchers studying animals at Chornobyl are also assessing the effects of detonated nuclear weapons. While scant research was done on nonhuman animals around Hiroshima and Nagasaki, hundreds of atomic weapons were tested elsewhere during the Cold War by the U.S. and the Soviet Union. According to Mousseau, a nonprofit called Visiting Veterinarians International, of which he and Betz are members, is studying dogs and other animals in the Marshall Islands and eastern Kazakhstan, where atomic bombs were detonated from the 1940s to 1980s.

Caring for the cattle of Fukushima

Fukushima, site of the Fukushima Daiichi power plant damaged by an earthquake and associated tsunami in March 2011, is another location for study, although not so much on dogs. Any dogs left behind, as well as any of their descendants, apparently struggled to survive as strays. Cats have proven more adaptable, according to the radiation exposure paper published this month. It cited research that involved the deployment of remote cameras across 106 sites in the 143-square-mile exclusion zone between May 2016 and February 2017. The cameras detected 1,269 cats and just 23 dogs.

A Japanese study of a small number of exposed cats and dogs handed to rescue centers in the immediate aftermath of the accident found the biological half-lives of cesium in their bodies was 30.8 days in cats and 38.2 days in dogs.

Researchers in Japan also have examined large animals, which, as a source of food for humans, present more obvious safety concerns. Following the accident in Fukushima, local authorities recommended that livestock in the exclusion zone be euthanized with the consent of their owners. Many opted instead to keep their animals alive.

Dr. Masahiro Natsubori is a member of a nonprofit that has been helping farmers take care of scores of Japanese cattle.

"Every year, we visit them and survey radiation activity, take blood tests and so forth," he said by email. The cattle still harbor significant amounts of radioactive cesium, he said, mostly on the outside of their bodies. But the researchers have found "no clear evidence" of acute health effects. Sporadic cases of lymphoma, Natsubori observed, likely have been caused by bovine leukemia virus, which is transmitted by blood-sucking midges.

The fieldwork will be of shorter duration than the radiation lingering in its subjects: All bulls in the exclusion zone were castrated following the accident to prevent uncontrolled mating that was increasing a herd population already deprived of adequate food and care. "As a result, which is very unfortunate for research purposes, no new calves have been born since the second year after the earthquake," Natsubori said.

Similarly, the dogs of Chornobyl may no longer exist within the foreseeable future. Through spaying and castration, the Dogs of Chernobyl's goal is to reduce the population to zero — something Betz hopes can be achieved in seven to 10 years' time.

"It will be very sad for me the day that the population decreases to zero, as caring for them has been a significant part of my life, and I care for them greatly," Betz said. "However, this is an industrial zone with obvious hazards. The dogs are not supposed to be in this area, and we are very grateful the [authorities] have allowed them to remain here for life instead of culling them."