Toxins released by long-extinguished fossil fuel fires and gold smelters are showing up in the bodies of Arctic wildlife, according to new research pointing to mercury released by pollution hundreds of years ago still circulating in ocean currents.
A paper published on Thursday in Nature Communications sought to untangle a paradox: why levels of the potent neurotoxin mercury in Arctic whales and polar bears are increasing — despite steps the world has taken to curb mercury pollution.
Those levels are now 20 to 30 times higher in Arctic wildlife than they were before the industrial era began, even as global mercury pollution has fallen since the 1970s.
“We’ve monitored mercury in Arctic animals for over 40 years. Despite declining global emissions since the 1970s, we see no corresponding decrease in Arctic concentrations — on the contrary,” coauthor Rune Dietz of Aarhus University, said in a statement.
The researchers’ conclusion: mercury released by pollution hundreds of years ago is still circulating in ocean currents, which convey it up to the Arctic.
The findings come amid reports that the Trump administration is seeking to overturn rules limiting the release of mercury from U.S. power plants — a step that reverses a long campaign to slow its accumulation in the atmosphere.
If these U.S. changes take place, the findings suggest, they will continue to contaminate the environment well into the 2300s.
Mercury — particularly forms that have been processed by bacteria — wreaks havoc on the brain and body, disrupting the ability of humans and animals to move, sense and think.
While a global effort has been successful in cutting levels of mercury in the atmosphere, Thursday’s findings point to a mystery: levels of the toxin in the muscle and tissue of top predators like seals and polar bears are still going up.
In addition to being released into the environment from burning fossil fuels, mercury is also used to purify gold extracted in small-scale or wildcat mining — a practice that is still common in the world’s forests, but has significantly decreased from its 19th Century peak.
In gold rushes like those in 1850s California or the modern Amazon, miners used mercury to bind together gold together from a slurry of dirt and ore, and then burn it off to leave pure gold — sending the mercury into the atmosphere.
From there, mercury rains down onto the land and flows into lakes and rivers, where bacteria break it down — as well as into the oceans, where that breakdown can take as much as 300 years.
The same quality that lets mercury pull together gold flakes gives it an insidious role in the environment because animals cannot easily purge it from their bodies.
That means mercury levels concentrate in the bodies of top predators — whether bears or humans.
The long duration of mercury in oceans gives it time to make its own epic journey from 19th Century smelters to the modern Arctic, the scientists found.
“Transport of mercury from major sources like China to Greenland via ocean currents can take up to 150 years,” Dietz said.
“This helps explain the lack of decline in Arctic mercury levels.”
Though China is working to phase out mercury mining and pollution from coal, the findings suggest a long lag time.
Even if mercury pollution continues to decrease, the scientists projected, its levels will continue to go up in the Arctic.
