Many Arctic pollutants continue their slow decline
Solid research on these chemicals requires many years of observation
It takes a long time, and a lot of patient field work and fancy math, to develop an accurate picture of how some pollutants are accumulating in the Arctic’s wildlife.
How long? “We need upwards of 20 years of data to draw conclusions with statistical confidence,” says Robert Letcher, a professor at Carleton University.
He’s one of 18 authors of a big research review, published last month in the journal Science of the Total Environment, that seeks to get a big-picture view of how persistent organic pollutants, or POPs, are working their way into Arctic species such as ringed seals from Resolute Bay.
These chemicals accumulate in the fat of organisms, growing in concentration as you move up the food chain. That’s not good for animals near the top of the chain, such as seals, polar bears, and people. Some POPs are associated with infertility and cancer.
For the review, Letcher and his colleagues reviewed more than 1,000 studies that collectively spanned much of the circumpolar world, from Alaska to Arctic Canada to Greenland and northern Scandinavia.
Unfortunately, many of the data sets didn’t offer the statistical rigor that the researchers had hoped to find, because the studies hadn’t been conducted for long enough.
“We only had enough statistical power for 12 per cent of the data sets,” said Letcher.
But the statistically solid studies did offer some important take-aways, in line with previous findings.
One is that so-called legacy POPs continue to decline in quantities in the Arctic, thanks to these chemicals being banned by the Stockholm Convention, an international treaty struck in 2001. These chemicals include DDT, an insecticide, and PCBs, used in electrical equipment.
“Over the past 23 years, they’ve consistently dropped in levels in things like sea bird eggs, polar bear fat, ringed seal blubber. That’s really a good news story: the monitoring, over the last 20 or 30 years, have shown these levels are going down,” said Letcher.
However, levels of PCBs aren’t falling as quickly as they used to. “In the past 10 years or so, their levels have kind of flat-lined,” said Letcher.
That’s probably due to old equipment littering parts of the Arctic that are slowing leaching these chemicals into the environment, he said.
“There are lots of depots of these things all over the place, especially in Russia. We don’t have a lot of data on these sorts of chemicals out the Russian Federation territory of the Arctic, which is a good chunk of the Arctic.”
Other sources of POPs within the Arctic include poorly managed local landfills, and melting permafrost, which is releasing mercury. However, most POPs are brought to the circumpolar region from more southerly latitudes, carried by prevailing winds and ocean currents.
There’s evidence that bans and phase-outs of a new generation of POPs are beginning to have an impact on the levels of these substances entering the Arctic. However, these declines aren’t as swift as researchers had hoped.
“We were expecting the levels of those to have gone down. And they have gone down a little bit, but not as much as we thought.”