Blood type diet

This is a posted article from the Usenet newsgroup misc.fitness.weights, it had
some formatting errors (it looked like a hastily executed cut&paste job) which I
have attempted to correct.
Decaying fish dump PCBs in Alaska’s lakes.
18 September 2003
MICHAEL HOPKIN
Salmon travelling to Alaska’s lakes to spawn are carrying large doses of
industrial pollutants with them, a study has shown10.
Environmentalists fear that the accumulation of these compounds, called
polychlorinated biphenyls (PCBs), could have harmful consequences for the
region’s top carnivores: bears, eagles - and humans.
Each summer, millions of sockeye salmon (Oncorhynchus nerka) make the 1,000-km
trip from the North Pacific back to the lakes where they were born. After
spawning there, they die, and their carcasses decompose in the lakes’ sediment.
The fish arrive loaded with PCBs from their oceanic feeding grounds, report

Jules Blais of the University of Ottawa, Canada, and his colleagues. In the
sediment of lakes with the most returning salmon, such as Frazer Lake on Kodiak
Island in southern Alaska, PCB concentrations can be seven times those in lakes
that receive no fish.
The results are akin to having a waste incinerator in Alaska’s wilderness -
pollution levels are as high as those in Lake Superior, close to the heavily
populated northeastern United States. “This is a remote, pristine environment,
but with PCB deposition comparable to an industrial site,” says Blais.
Salmon cart chemicals - good and bad - upstream, agrees ecologist David
Schindler of the University of Alberta, Canada. Dying fish, for example, furnish
the lakes with vital nutrients. “If they can transport nutrients, they can also
transport things that are not quite so beneficial,” Schindler says.
Vicious circle
The problem is bioaccumulation - the build-up of contaminants in creatures at
the top of the food chain. The North Pacific contains about 1 nanogram of PCBs
per litre. By the time the average salmon has finished bulking up for its
journey, its fat contains about 160 micrograms, Blais and co-workers report.
“The salmon are perfectly fine for eating,” says Blais. But dead fish become
fodder for insects at the bottom of the food chain, triggering a fresh round of
bioaccumulation. “There’s a snowball effect,” Blais explains.
PCBs are released into the environment by the manufacture of materials such as
flame-retardants and paints, and by burning waste. Their effects on human health
are not clear, but are thought to include reproductive defects, memory
impairment and reduced hand-eye coordination. PCBs break down very slowly, so
they can spread widely and be difficult to track.
A case in point is Lake Laberge in Canada’s Yukon Territory. In the early 1990s,
PCB pollution - thought to have arrived by air from Eurasia - reached such a
level that the inhabitants of this otherwise pristine area were warned not to
eat trout from the lake. “PCBs have a way of producing surprises,” says Blais.
The situation may improve in the future, Schindler predicts. Industrial PCB
emissions have been falling for more than 20 years. “This could turn out to be
one of the few
environmental problems that we have dealt with in good time.”
References
1.Krümmel, E. M. et al. Delivery of pollutants by spawning salmon. Nature, 425,
255 - 256, (2003).

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