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A new study says some of Alaska's pristine and remote lakes are getting polluted with industrial PCBs through an unlikely source: sockeye salmon.
The fish pick up the chemicals in the northern Pacific Ocean and return to the lakes to spawn. Then they die, their bodies releasing the pollutant and raising PCB concentration in the lake sediment more than sevenfold in some cases, researchers conclude in Thursday's issue of the journal Nature.
It's not clear whether the pollution is affecting the wildlife in the lakes by weakening their disease resistance or causing other effects, said researcher Jules Blais of the University of Ottawa in Ontario, Canada.
The lakes are too far from human populations to pose any hazard to people, and the PCB concentrations in the lake sediments are too low to justify cleanup projects in any case, he said. Blais said the salmon don't contain enough PCBs to be hazardous if eaten.