Salmon Bring Pollutants North
INTRO: Scientists have long known that industrial chemicals make their way into pristine environments through the air and water. But recently they discovered that pollution is hitchhiking its way to the Arctic aboard an unexpected carrier. Doug Schneider has more in this week's Arctic Science Journeys.
STORY: Soon after they're born in freshwater rivers and lakes, Alaska's salmon migrate to the open ocean, a place where pollution is also found. But it was only recently that anyone checked to see if salmon returning home to spawn were bringing that pollution back with them. Turns out, they are.
In a study published in the March issue of the scientific journal "Arctic," Swedish scientists, led by Goran Ewald, studied sockeye salmon migrating up Alaska's Copper River. They found that the salmon contained low levels of PCBs and the pesticide DDT, and that salmon passed these pollutants on to other fish such as grayling.
EWALD: "I was quite sure about finding pollutants in the salmon. I mean pollutants are present everywhere on our planet now. But that the pollutants would actually be transferred to the grayling was the new point. I was quite surprised that it was so clear."
DDT and PCBs are believed to cause cancer in humans. Both have been banned in many developed countries, including the United States, since the 1970s. But they are still used elsewhere, and they continue to accumulate in the global food chain.
Ewald says sockeye salmon accumulated PCBs and DDT in their fat while feeding in the Pacific Ocean. As the salmon migrated home, they burned that fat for energy. Yet the chemicals, rather than being metabolized, instead increased in concentration in the fish's remaining fat and roe. When the salmon died after spawning, the pollutants were passed to grayling that ate the carcasses and eggs. Goran Ewald.
EWALD: "Grayling feed directly on the salmon eggs, and the pollutants are present in the eggs. After spawning, all the salmon die and decompose in the lake. The grayling feed directly on the salmon carcasses. Otherwise the pollutants are released and accumulate in the organic material."
Ewald's study was intended only to show how industrial pollution makes its way into pristine parts of the globe. But in Alaska, where salmon sustains a fishing industry worth about 300 million dollars each year and where thousands of people depend on the annual return of salmon for basic food needs, news reports that portrayed Copper River salmon as tainted have left the fishing industry scrambling to protect its image. Cheri Shaw is the executive director of the Cordova District Fishermen United, a fisherman's organization that promotes Copper River salmon.
SHAW: "My first reaction was of pure shock. My organization has really put a lot of effort into promoting the Copper River salmon and the salmon opening to the domestic market in the Lower 48. This couldn't have come at a worse time."
Of course, the real question is: are Alaska's salmon safe to eat? Goran Ewald believes they are. He says pollutant levels in Copper River salmon are at least 20 times less than federal standards, and less than in fish from other parts of the world.
EWALD: "The levels are extremely low. I don't think you could find lower levels in other fish species. Comparing it to the Great Lakes, the Baltic, the Atlantic, the Mediterranean and so on, these are extremely low concentrations."
Michael Watson is the senior toxicologist with the Environmental Protection Agency in Seattle. He says people should have no misgivings about eating Alaska salmon.
WATSON: "This is a nothing problem as far as human health. It's an academically interesting question about how do PCBs and DDT find their way back into the environment, but that's all it is. I think it's a trivial issue. The benefits of eating Copper River sockeye so far eclipse the risk."
Although human health isn't at risk, Goran Ewald says the message his study sends is that pollution is making its way into the once-pristine Arctic. He says pollution should be monitored, as contaminants will continue to accumulate in the northern food chain as salmon return each year with fresh stores of pollutants.
But money to monitor the problem is unlikely at a time when the state is cutting its budget, says Phyllis Weber-Scannell of the Alaska Department of Fish and Game.
SCANNELL: "There really are not at this time the resources available at this time, either in people to do the work or money to do the kind of work such as Dr. Ewald has done. It's way down there on the priority."
Considering the importance of salmon to the state and the nation, Goran Ewald hopes that Alaska will change its priorities.
EWALD: "I would appreciate it very much if you could bring the message to Alaskans and that is that the pollutant concentrations are low, and that you should really do whatever you can to keep them that way.
OUTRO: For Arctic Science Journeys, this is Doug Schneider, reporting from Fairbanks, Alaska.
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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