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Study maps pollution’s pathway to the Arctic, sets path for future research

MIT researchers have built a model that will be further developed as part of an NSF-funded project to track how chemicals get to remote Arctic environments.

It's been more than a decade since global leaders met in Stockholm, Sweden, to sign a treaty with the goal of eliminating persistent organic pollutants making their way into our food chain — such as harmful pesticides like DDT that nearly wiped out the American Bald Eagle. While leaders have come a long way in restricting these types of pollutants, contamination of the Arctic remains a problem. Researchers at MIT are working to help inform policies that more effectively address contamination problems with their latest research and the help of a new grant from the National Science Foundation.

"Persistent organic pollutants are chemicals of substantial international concern," Noelle Selin, the project's lead researcher and assistant professor in MIT's Engineering Systems Division and Department of Earth, Atmospheric and Planetary Sciences, says. "For emerging contaminants in the Arctic, we need to know more about their sources, environmental behavior, and transport pathways in order to regulate them more effectively."

Selin and Carey Friedman, a postdoctoral associate at the MIT Joint Program on the Science and Policy of Global Change, had their latest results published last week in the journal Environmental Science & Technology. The study, Long-Range Atmospheric Transport of Polycyclic Aromatic Hydrocarbons: A Global 3-D Model Analysis Including Evaluation of Arctic Sources, describes the researchers' development of a detailed 3-D atmospheric model used to track the day-to-day transport of chemicals. Specifically, they tracked PAHs — toxic byproducts of burning wood, coal, oil and other forms of energy that remain in the atmosphere for less time than other persistent organic pollutants regulated by global standards.

"Even though our model estimates lifetimes less than a day, that's still long enough for these PAHs to travel long distances and have potentially damaging effects," says Friedman, the study's lead author, noting that some of these chemicals are known carcinogens that could cause cancer. "So PAHs may be a good case study of how we regulate long-range transport."

Friedman's work will be an important foundation for ongoing work in Selin's research group at MIT, in collaboration with the University of Rhode Island and the Harvard School of Public Health. Together the researchers will be exploring the global transport of other contaminants in the Arctic, such as chemicals used in stain-resistant carpets and non-stick pans. In research going forward, Selin and her team will extend the model created in their recent analysis that allows them to track chemicals with much greater precision.

"These more complex models are showing what simple models aren't, such as daily fluctuations of pollutants in specific locations," Friedman says, "So while the simple models are important for some aspects of the policy process, they may not provide enough information to base these types of important decisions off of."

The presence of these pollutants in the Arctic is important for several reasons. First, the researchers say there's a very real health concern. Organic pollutants typically condense and rain down into Arctic regions. Once they mix with other chemicals, it's unknown what danger they could pose to animals and humans, especially in concert with climate change stressors in the Arctic. Already, these chemicals are known to build up in the fat of whales, seals and other animals — a main source of food for people living in these high latitude regions.

At the same time, the practices that create some of these chemicals such as gas and oil exploration and shipping are expected to increase in the Arctic. As they do, it's important to understand how pollutants traveling from distant sources exacerbate the problem, and how climate changes can affect future contamination.

"Climate change and contaminants are both substantial present and future threats to the Arctic, and our research can ultimately help leaders make better policies to protect this unique environment," Selin says.

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