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Pollutants Steadily Decreasing in the Arctic

Four Arctic scientists from Environment and Climate Change Canada - Robert Letcher, Birgit Braune, Derek Muir, and Marlene Evans - joined colleagues from other polar nations to look into persistent organic pollutants (POPs) in the Arctic. Their article "Temporal trends of persistent organic pollutants in Arctic marine and freshwater biota" was published earlier this year in Science of The Total Environment.

Photo :Descending a cliff to monitor pollutants affecting Arctic seabird colonies

Descending a cliff to monitor pollutants affecting Arctic seabird colonies. Photo credit: Grant Gilchrist

What are POPs?

POPs are particularly problematic chemicals due to their long lifetime and their tendency to be transported long distances. They include such chemicals as the insecticide DDT (dichlorodiphenyl-trichloroethane) and PCBs (polychlorinated biphenyls)—chemicals produced in industrial processes. Over time, POPs have made their way north into the Arctic through the atmosphere and ocean, negatively impacting Arctic life.

"[POPs] are still found in the environment at levels that may cause adverse effects to the health of top predators in Arctic food chains. Humans living in the Arctic and consuming significant amounts of high-trophic traditional food are exposed to legacy POPs, which may lead to adverse health effects," the report states.

Robert Letcher, one of the authors of the study, describes removing POPs as "a monumental task . . . because there was so much produced in the twentieth century."

Thanks to the Stockholm Convention, twenty-eight POPs have been banned as of 2017. However, even some POPs that were banned as early as the 1970s are still being found in the environment. Given that the Convention is voluntary, there are still difficulties in controlling the production of such chemicals.

Researchers covered a vast swath of territory to monitor POPs. The region studied stretches all the way from Alaska, USA, in the east to northern Scandinavia in the west. They examined more than a thousand time series of POP data in these Arctic ecosystems.

What did the results show?

In a nutshell, Letcher described the findings as a good news story.

Since the 1980s, there has been a decrease in concentration of most POPs in the Arctic. This finding is especially true in the case of HCH (hexachlorocyclohexane), which was used as an insecticide before being phased out in the 1970s in many polar countries, including Canada.

The results show that increased regulations have been effective.

"A large number of time series covering a large geographical area and including different matrices show consistency and agreement in the POP trends. These results provide indications of the effectiveness of national and global controls," the study says.

In some cases, there were relatively rapid changes following the implementation of regulations and voluntary measures to reduce POPs.

Nevertheless, there are still some opportunities for improvement.

For example, one POP—HBCDD (hexabromocyclododecane)—showed some increases during this time period. There were also some increases of certain POPs in specific locations, largely due to more localized pollution sources. As well, the decreases in some POPs have not been as rapid as they have been for others.

What’s next?

Climate change is a huge challenge that researchers are examining. Letcher describes it as the biggest stressor in the Arctic. With climate change comes the reality of shifting diets and new invasive species, which could mean animals may be exposed to different POPs.

Over the coming years, Canadian researchers and their international colleagues will continue to monitor POPs in the Arctic to add to their data set.

Letcher emphasizes determining trends takes time: "It takes many years to build up enough data to see if there is a change . . . we need more years to build enough of a data set with the power to conclusively conclude on what the temporal changes are."

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