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Chemistry

Fireproofing the Arctic

The Paper

Li, J.; Xie, X.; Mi, W.; Lai, S.; Tian, C.; Emeis, K.; Ebinghaus, R. Organophosphate esters in air, snow, and seawater in the North Atlantic and the Arctic. Environ. Sci. Technol. 2017. DOI: 10.1021/acs.est.7b01289

Manmade Molecules, Built to Last

There are thousands of manmade chemicals added to the products we use every day to improve their performance. Some lower the ignitability of our couches and rugs so they can’t catch fire as quickly (flame retardants), and others increase the flexibility and stability of plastic products (plasticizers). The best chemicals for these types of jobs are ones that are very stable, even under extreme conditions.

However, there’s a significant downside: chemicals that are stable enough for everyday use are often remarkably stable in the natural environment as well. Even if we realize one of these chemicals is toxic and stop using it, it could persist in the environment for decades and travel far from the location where it was originally used, affecting ecosystems in far flung, fragile regions like the Arctic.

Organophosphate Esters

In the study described here, researchers from Helmholtz Zentrum München, University of Hamburg, and MINJIE Analytical lab in Germany, and from South China University of Technology and the Yantai Institute of Coastal Zone Research in China joined forces to measure one group of manmade molecules, the organophosphate esters, in remote regions of the North Atlantic and Arctic Ocean.

Organophosphate esters, or “OPEs,” are used in a wide range of applications – as flame retardants, plasticizers, and additives in other industrial products. Based on their molecular structure and properties, experts had predicted these compounds would be broken down in the environment pretty readily, and shouldn’t be able to travel to remote Arctic regions. However, recent studies have detected OPEs in the air of the European and Canadian Arctic at alarmingly high levels.

Evidence that OPEs might be persistent and capable of traveling far from their sources has worried scientists and environmental advocates, particularly because OPEs have been used in increasing volume over the past decade to replace other types of flame retardants that are known to be harmful and persistent. What’s more, recent studies have shown that some OPEs can cause cancer and disrupt normal hormonal functions in aquatic organisms and humans. This has led scientists to wonder:

Are these OPEs really any better for the environment than the toxic flame retardant chemicals they’re replacing? Could they be even worse?

An Expedition Aboard the R/V Polarstern

The R/V Polarstern, an ice breaker from the Alfred Wegener Institute in Germany. Source: Wikimedia Commons.

Scientists embarked on an expedition aboard the R/V Polarstern, an ice breaker that has been traveling throughout the remote Arctic for 30 years on scientific expeditions. They gathered samples of snow, seawater, and air from various locations in the North Atlantic and Arctic regions to learn more about OPEs in remote environments. You can see the cruise track they followed here, and check out the Polarstern’s blog here.

Because OPEs are present in many products we use every day, the scientists had to be extra careful not to contaminate their samples with OPEs leaching out of scientific equipment and consumer products on the research vessel. They monitored levels of OPEs on the ship’s upper deck and in the chemistry lab to make sure the pollutants they were detecting really came from the seawater, snow, and air samples they were collecting, and not from the ship.

Flame Retardant OPEs: Particularly Persistent

OPE concentrations in seawater are shown here, with the bigger bars representing higher concentrations. Concentrations were dominated by the compounds marked by red and blue (TCPP and TCEP), which are chlorinated OPEs. The concentrations were greatest near populated European regions, where these compounds are used, and also increased near coastal regions in higher latitudes due to snow and glacier melt. Source: Reprinted with permission from Li et al., Environ. Sci. Technol., 2017. Copyright 2017 American Chemical Society.

Scientists found that total concentrations of OPEs in air and seawater were decreasing as they travelled further from Europe and out into remote, less populated areas. This was expected, as pollutants that are currently being used are usually found at the highest levels near their point of origin.

Results from the study showed that a few specific OPEs, specifically the chlorinated ones, which are typically used as flame retardants, were the most abundant OPEs in remote, high latitude regions. This is an indication that the chlorinated types of OPEs are generally more persistent and capable of traveling long distances than the non-chlorinated molecules.

By analyzing spatial data, the scientists came to the conclusion that there are numerous sources of OPEs to the Arctic environment. They surmised that OPEs are being carried in the air from developed regions and deposited in remote ocean environments, and may also be entering the Arctic by traveling through rivers. They also observed that some portion of the OPEs they measured may be coming from local sources, such as human activity in the Arctic, rather than traveling from lower latitudes.

Flame Retardant Snow

Polar ice loss is accelerating due to global warming, and with it will come increasing levels of persistent pollutants in polar ocean waters. Source: NOAA, climate.gov

The researchers found that concentrations of OPEs in seawater decreased as they moved away from remote coastal areas toward the open ocean. This was an indication that snow and glacier melt were acting as secondary sources of OPEs to the Arctic Ocean. After being emitted from a primary source (the human activity or product they originated from), these OPEs had found a resting place, becoming stored in the snow, but were then remobilized due to changes in the environment (melting snow).

This finding is worrying when considering that immense changes the Arctic faces due to climate change. Warming in the Arctic could cause large amounts of stored OPEs and other persistent pollutants to be released from ice and snow, making them freely available in the water, where they could harm aquatic life.

The Importance of Polar Research

Information on pollutant levels in remote polar regions is indispensable for scientists who want to understand how pollutants move around the globe. Data on Arctic pollution give us an idea of the “global background” for persistent pollutants: how pervasive are these chemicals in areas where they’re not being used, far from the centers of human activity? Detection of OPEs in the Arctic is a fairly strong indication that these compounds do not break down readily in the environment, as originally expected, and exhibit many of the same properties that got previous classes of flame retardants banned.

I am the founder and editor-in-chief of oceanbites, and a postdoctoral fellow in the Higgins Lab at Colorado School of Mines, where I study poly- and perfluorinated chemicals. I got my Ph.D. in the Lohmann Lab at the University of Rhode Island Graduate School of Oceanography, where my research focused on how toxic chemicals like flame retardants end up in our lakes and oceans. Before graduate school, I earned a B.Sc. in chemistry from MIT and spent two years in environmental consulting. When I’m not doing chemistry in the lab, I’m doing chemistry at home (brewing beer).

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