Researchers have long known that heavy metals and persistent organic pollutants such as DDT concentrate in the Arctic, in top predator animals like polar bears.

But what happens with animals like Svalbard’s reindeer, which graze on arctic plants?

How contaminated are these animals? How do they compare to other reindeer species, such as caribou, across the Arctic? What kinds of effects might those contaminants have? And lastly, people eat Svalbard reindeer. Do they need to cut back?

That knowledge gap led Malin Andersson Stavridis, who recently defended her PhD at the Norwegian University of Science and Technology (NTNU), to spend four years in the northern archipelago of Svalbard to find the answers.

What she found was that levels of toxic metals in the animals – such as cadmium, lead and mercury – have been relatively stable for the last decade.

But what really shocked her was that levels of so-called forever chemicals, PFAS, have skyrocketed over that same period.

PFAS levels had spiked so precipitously that “I thought they must be wrong,” Stavridis said.

“To see that the concentrations are so high, maybe even the highest measured in reindeer, that was a not an ah-ha moment, but more like ‘what the heck?’” she said.

Her latest study, on exposure and accumulation of heavy metals and PFAS, or “forever chemicals,” in Svalbard reindeer, has just been published in Environmental Science and Technology.

One of the challenges Stavridis faced was how to measure meaningful contaminant levels in the animals.

Earlier studies had relied on testing reindeer poop and hair to get this information. That’s an easy, non-invasive way to collect samples. But these sampling methods don't necessarily give a full picture of how pollutants may be affecting the animals.

“I was asking myself, can we say anything about the contaminants inside? Can we determine the contaminants in liver or soft tissues just based on what's in the fur? And I felt like that link was missing, especially since Svalbard reindeer are also consumed by people living on the island,” she said.

She was lucky enough to piggyback on a huge international, interdisciplinary research project funded in part by the Research Council of Norway and the Svalbard Environmental Protection Fund and approved by the Governor of Svalbard in which 68 female reindeer were culled over three years.

That’s how in October, 2021, she found herself taking brain, kidney, liver, faeces and thigh samples from humanely culled Svalbard reindeer.

The following two years she would analyse fur, faeces, muscle and liver samples to determine contaminant concentrations.

Mercury in the Arctic comes from natural sources, such as from forest fires or volcanoes. It’s also emitted as fossil fuel is burned.

Mercury can be airborne and ride the wind northward, or it may arrive in the bodies of fish and mammals that consume it in their food and concentrate it. Airborne mercury can be taken up by plants through the openings in their leaves, which is why the Arctic’s frozen soils contain a vast pool of the toxic metal, Stavridis said.

“Permafrost soils are just old plants that have been slowly building up over time. So that's how we have this very big accumulation of mercury in Arctic soils,” she said.

As their name suggests, these soils are permanently frozen, with a top layer that can freeze and thaw every year.

Of course, global warming is causing permafrost to thaw.

“So in that context, I just wanted to lay the foreground for how we can determine whether mercury concentrations are becoming bioavailable?,” she said. “How will we know what is happening to the mercury in the Arctic if we don't know what levels look like now?”

In the end, by comparing the different types of measurements, she was able to confirm that faeces could be used to monitor mercury levels in the animals. That’s good news, because for this one element in particular, there was no need to cull animals to keep tabs on this important contaminant.

Stavridis didn’t just want to take a snapshot of contaminants in Svalbard reindeer, she also wanted to know how these levels changed over the summer. Summertime is when reindeer are actively grazing and building up body fat so they can survive Svalbard’s long, dark, icy winters.

After that first sampling session in 2021, she took samples in August 2022 and October 2023. October is key because that’s when the animals are reaching their highest weights. They’re putting on fat to survive the long, dark arctic winter.

That matters for the reindeer themselves, but it also matters for hunters on Svalbard. The hunting season starts in mid-August and ends in late September. Hunters are limited to one animal a year.

Not surprisingly, she found that contaminants such as mercury, cadmium and PFAS were higher in October than in August.

But levels of two other toxic metals, cadmium and lead, had decreased compared to levels reported in the 1980s.

Most of these contaminants were similar to, or lower than what has been found in other reindeer subspecies across the Arctic. But not PFAS levels.

These were among the highest of all the reindeer across the Arctic and had increased dramatically over the past decade, she said.

In the last decade, she found, PFAS levels increased by more than 900 per cent, from roughly 0.6 nanograms per gram to 5.48 nanograms per gram.

The chemical “fingerprint” of PFAS from previous studies suggested the previous source of forever chemicals was from firefighting training in Longyearbyen.

But the latest measurements, in addition to being so high, also showed a different chemical fingerprint.

“Now we see a profile that's dominated by another type of PFAS, and that the concentrations are so high, maybe even the highest measured in reindeer,” she said.

The reason behind this dramatic increase remains a mystery, however.

“I only have my samples from the reindeer to go from. I can say that there is something that has affected their exposure. It could be as simple as they have a different diet,” she said.

But she isn’t satisfied with that answer.

“Even if they have a different diet, the levels shouldn't change that much in 10 years,” she said.

There are limits as to what kinds of genetic studies Stavridis could do, because of the way samples she collected had to be handled.

Nevertheless she was able to screen for 20 different genes to see if they were upregulated, meaning that they might produce more of the substances they play a role in making, or downregulated, meaning that they would produce less.

Many of the genes she studied were related to lipid – or fat – metabolism, and appeared to be downregulated with increasing contaminant concentrations.

“Building fat and using fat is very important for these animals because they are undergoing such large fluctuations in body mass throughout the year,” she said. “This is such a vital function to have in an Arctic animal.”

Similar studies in polar bears and orcas have shown much the same, she said.

In this case, she found this association when the animals contained higher levels of a cocktail of contaminants. This particular cocktail contained a family of PFAS that has been found more recently in reindeer, plus mercury and cadmium.

In the end, Stavridis found that each of the individual contaminant concentrations in Svalbard reindeer are below current wildlife toxicity thresholds. But the genes she studied suggested that even if individual contaminants are low, the combination can have an effect.

She also found that the animals can be eaten, but with limits. Svalbard allows hunters to take one animal per hunter per season. That means the overall exposure isn't that high.

However, “if a person wants to eat Svalbard reindeer, they can only consume 11.5 grams of liver per week over a year so as to not exceed the PFAS threshold,” she said.

Svalbard reindeer are “out there. They’re wild. They’re in the middle of nowhere,” she said. “So this is one pathway of exposure from something that you would assume is completely safe. And yet here we are.”