Levels of mercury in Arctic wildlife could continue to rise significantly even as countries curb their emissions, a new study suggests.
Researchers analyzed more than 700 samples of fish, mammals and peat collected across Greenland over the past 40 years and found evidence that the mercury in them was distributed by ocean currents.
The finding, published this week in the journal Nature Communications, helps explain why levels of mercury contamination have continued increasing in the Arctic even as global emissions have begun to plateau.
“We got a lot of surprises when we analyzed the data,” said Jens Sondergaard, a senior ecological science researcher at Aarhus University in Denmark and lead author of the study. “It’s a really striking trend.”
Exposure to high concentrations of mercury, a potent neurotoxin, can lead to neurological and other health-related effects and the study confirms that mercury emitted today could continue posing a large threat to humans and wildlife in the region for centuries.
eBy analyzing mercury isotopes, a unique kind of chemical signature that can be matched like a fingerprint, the researchers traced the spread of mercury contamination to the patterns of ocean currents around Greenland. Previous research has shown that mercury can persist in oceans for more than 300 years.
The results indicate that large, century-old stores of mercury in the ocean could actually be the dominant means by which the element proliferates through marine ecosystems in the Arctic, Dr. Sondergaard said. This poses a problem for people who live in the region, particularly Inuit communities that hunt large marine mammals with high concentrations of mercury, like seals.
“It’s a quite unique situation. This population that ought to be, you know, in a clean environment, has some of the highest concentrations,” said Rune Dietz, a professor at Aarhus University and a co-author of the study.
Mercury is primarily spread through the environment by human activities such as burning coal or mining heavy minerals, like gold. According to a 2023 estimate by researchers at the Harvard School of Engineering and Applied Sciences, atmospheric mercury concentrations have risen nearly sevenfold since the 1500s.
Mercury emissions in North America and Europe began falling in the 1970s, following the enactment of a series of environmental regulations like the Clean Air Act. Other countries with high levels of pollution, like China and India, began curbing their emissions a little more than a decade ago, after signing a global agreement known as the Minamata Convention.
Earlier this week, the Environmental Protection Agency began moving to loosen limits on mercury emissions, along with those on other pollutants, from power plants.
There is no known safe level of methylmercury, the toxic form of mercury that can form in aquatic environments. In high bodily concentrations it can cause neurological problems, kidney damage and affect fetuses in the womb.
Despite hosting almost no mercury-producing industries, the Arctic has become a hot spot of contamination, in part because of the natural pattern of the Earth’s atmosphere and oceans, which tend to circulate pollutants toward higher latitudes.
Large predators that eat significant amounts of contaminated prey end up ingesting the most mercury. Studies have shown that such marine mammals, like ring seals and pilot whales, can carry concentrations of mercury up to 50 times greater than some smaller fish, like herring. The new paper found that concentrations of mercury found in polar bear tissues have doubled in the last 40 years.
Niladri Basu, a professor of environmental health sciences at McGill University in Canada who was not affiliated with the study, said that Indigenous groups with hunting practices are most at risk for exposure to mercury. “The species that drive exposure in communities are not species that are harvested for global transport and trade,” he said.
Dr. Basu added that mercury advisories have led to some Inuit communities cutting back on traditional food sources, representing a significant cultural loss.
Emissions aren’t the only mercury contamination threat in the Arctic. In 2024, a study found that the region’s frozen soils, known as permafrost, have been accumulating mercury for centuries, reaching levels estimated to be higher than the atmosphere, oceans and life-forms combined. As climate change continues to warm the planet, scientists worry that these stores of mercury could be released.
In November, international delegates will meet for the Minamata Convention’s sixth major meeting. This year also presents the first deadline for the more than 120 countries who signed on to the treaty, to begin phasing out mercury use in certain types of production.
Even in light of the global action on mercury, Dr. Basu said, it could take centuries for the Arctic to recover.
“On one hand, we want to take action, and we have to recognize that mistakes are made and that we can’t continue as business as usual,” he said. “But on the other hand, we have to recognize that it’s going to take a long, long time to undo all the damage.”
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