U.S. Water News Online
ONTARIO, Canada -- 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
then 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 have
concluded in a recent issue of the journal Nature.
It's not yet 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
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 his work found the salmon themselves don't contain
enough PCBs to be hazardous if eaten.
An Alaska state environmental official said the study's
conclusions about the lakes would have to be confirmed by further
Blais said the study shows what can happen if enormous numbers of
the fish concentrate in small lakes, but it focuses on extreme
examples of that and doesn't represent Alaska lakes or rivers in
``Maybe the message here is that when we release these chemicals
into the environment, a lot of unexpected things can happen,'' Blais
PCBs -- polychlorinated biphenyls -- concentrate in food chains,
and killer whales near British Columbia have accumulated higher
levels apparently by eating contaminated salmon and seals, he said.
Blais and colleagues chose eight lakes on Kodiak Island and the
nearby Alaska mainland that have a wide range of densities of
spawning salmon. They collected samples of lake sediment during 1995,
1997, 1998 and 2002.
They found that in general, the higher the concentration of
spawning salmon a lake had, the higher the PCB concentration in its
sediment. That suggests the salmon were responsible for the variation
in PCB levels.
Kristin Ryan, director of environmental health at the Alaska
Department of Environmental Conservation, said more research is
needed to see if the salmon idea is true. PCB pollution in Arctic
areas such as Alaska is generally blamed on transport of the
chemicals through the atmosphere, she said.
They lakes studied were Frazer, Karluk, Red, Olga, Spiridon,
Becharof, Ugashik and Illamna.
Researchers said their samples had a range of densities of salmon
return from zero to 40,000 spawners per square kilometer.
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