Contain More Pollutants
Farm-raised salmon contain significantly
more dioxins and other potentially cancer-causing pollutants than
salmon caught in the wild, says a study that could confuse consumers
long told the fish is heart-healthy.
The study tested contaminants in 700
salmon bought around the world and found those farmed in Northern
Europe contained the most pollutants, followed by North America
and then Chile.
Eating more than a meal of farm-raised
salmon a month, depending on its country of origin, could slightly
increase the risk of getting cancer later in life, according to
the study published Thursday in the journal Science.
Researchers blamed the feed used on fish
farms for concentrating ocean pollutants. It advised farmers to
switch feed and recommended that consumers in the meantime eat
more wild salmon.
But the study's conclusions are controversial.
The U.S. Food and Drug Administration insisted that the levels
of pollutants in farm-raised salmon are too low for serious concern
and urged consumers not to let the new research frighten them
into a diet change.
The study "will likely over-alarm people
in this country," said Eric Rimm of the Harvard School of Public
Health, a specialist on nutrition and chronic disease. "To alarm
people away from fish because of some potential, at this point
undocumented, risk of long-term cancer - that does worry me."
The American Heart Association advises
eating fish at least twice a week because it helps prevent heart
disease. Salmon is usually listed as a top choice because it is
particularly high in heart-healthy omega-3 fatty acids and low
in a completely different seafood contaminant, brain-harming mercury.
Most farm-raised salmon sold in the United
States come from Chile and the pollutant level in this salmon
was not too much higher than that found in some wild-caught salmon.
In addition, the study tested salmon
raw, with the skin on. Removing the skin and grilling it removes
a significant amount of PCBs, dioxins and other pollutants stored
in fish fat, the FDA noted.
"We are certainly not telling people
not to eat fish," said David Carpenter of the University at Albany,
N.Y., who led the new research. ". . . We're telling them to eat
less farmed salmon."
Farm-raised salmon contained significantly
higher concentrations of 13 organochlorine pollutants, he found.
Among the most important are dioxins, which are released when
industrial waste is burned, and PCBs, once widely used as insulating
The average dioxin level for farm-raised
salmon was 11 times higher than in wild salmon - 1.88 parts per
billion compared with 0.17 ppb. For PCBs, the average was 36.6
ppb in farm-raised salmon and 4.75 in wild.
Animals absorb those pollutants through
the environment, storing them in fat that people then eat. High
levels are believed to increase the risk of certain cancers and,
in pregnant or breast-feeding women, harm the developing brains
of fetuses and infants.
The salmon farming industry points out
that all the pollutant levels are well within the FDA's legal
limits and says other foods eaten far more often, such as beef,
are more important sources of exposure.
The U.S. government has set no safe level
of dioxins and PCBs in foods. In setting his consumption advice,
Carpenter cited Environmental Protection Agency guidelines that
are far stricter than the FDA's legal limits.
Farm-raised salmon eat lots of fish oil
and meal made from just a few species of ocean fish, concentrating
the contaminants they're exposed to - while wild salmon eat a
greater variety, he explained.
Raising salmon in floating pens is an
industry that began just two decades ago but has helped the fish's
popularity to soar. More than half the world's salmon now is farmed,
available year-round while wild salmon is generally available
June through October. Farm-raised salmon can also sell for about
a third of the cost of wild salmon, said Alex Trent of the trade
group Salmon of the Americas.
Many farmers in the United States, Canada
and Chile are slowly replacing some of the fish oil in salmon
feed with soybean and canola oil to address the pollutants, Trent
"PCB levels are coming down 10 to 20
per cent a year," he said. "Every year we take more steps."
One in two Americans will die of cardiovascular
disease, a far bigger risk than the cancer concern, said nutritionist
Alice Lichtenstein of the Agriculture Department's Human Nutrition
Research Center at Tufts University.
Still, "this was a beautiful study" that
does raise a concern that needs more attention, she said. "The
bottom-line message is to continue to eat fish but consume a variety
of different types."
As for the geographic difference in contaminant
levels, ocean pollution follows a similar pattern. Europe was
industrialized before North and then South America, and presumably
each region uses salmon feed made of local ocean fish.
The study was funded by the Pew Charitable
Reference Source 102