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The Return of the Ice POPs

Our past crimes were laid on ice, but now are coming back to haunt us

Sareghi Carega
Sareghi Carega in a coral reef. Oceans are receiving persistent organic pollutants from industry from all over the world

Pollutants in the atmosphere, released by industry in North America and Europe, have been found in icesheets all over the world, where they have been sitting like a time bomb, waiting for a chance to return to bring us to account.

That chance has come with accelerating global warming. Seals in the Arctic show spikes in the levels of PCBs during low-ice years, and lake sediments in Europe are filling up with toxic contaminants from the melting glaciers. Umwelt.Science follows up the story through the results of two research teams, one in Canada and one in Switzerland.

For decades, industry in Europe and North America were able to pump toxic chemicals into the seas and air without much hindrance. Many of these were persistent organic compounds (POPs). Their persistence means they typically have half-lives of the order of decades, and as a result once allowed to enter the biosphere can circulate around the planet, riding on sea and air currents.

The worst thing about them is that they are taken in by organisms such as algae and fish, and biomagnify up the food web to birds, whales and seals, and eventually into humans. Polychlorinated biphenyls and other POPs are readily absorbed by fat, and marine mammals have been found with very high concentrations, accumulated over many years.

Climate change is real and now, and the effects are not evenly distributed. The poles are heating up twice as quickly as the global average. As the ice in the Arctic melts, the POPs and other pollutants they contain are being released back into the sea, where they are ingested by organisms, such as plankton and fish. These are eaten in large numbers by larger creatures, such as seals and whales, and accumulate in their bodies. By the time they arrive on the human menu, the dose has magnified to dangerous levels.

Researchers in North Canada[1] have been measuring the variation in concentrations of PCBs and mercury in seal blubber for three decades. They have discovered that the concentrations increase in low-ice years, when warming is greatest. Since these pollutants would have travelled around the planet in sea and air currents, before being deposited in the ice, it seems likely that they have contaminated ice everywhere.

Oberaar Lake
Oberaar Lake, near Bern, Switzerland

This disturbing idea has been confirmed closer to home, in central Europe. The Oberaar Lake, near Bern, Switzerland, has sediments containing high levels of pollutants, such as pesticides banned since the 1970s. Glacier melt has released these chemicals back into circulation, find a team from the Swiss Federal Institute of Technology, ETH[2]. If the glaciers continue to melt, there is little that can be done to prevent the releases.

1 Research team leader: Gary Stern, of Canada's Department of Fisheries and Oceans in Winnipeg, Manitoba

2 Research team leader: Christian Bogdal, an environmental chemist at the Swiss Federal Institute of Technology, Zurich (ETH)

Article by Andrew Bone, Sunday, 19th June 2016