Organic Consumers Association

Study Shows Farmed Salmon Contain Dangerous Levels of Toxic Chemicals

Farmed salmon harbour pollutants
Study may undermine salmon's status as a 'healthy' food.
9 January 2004
Nature Magazine


Salmon is high in healthy omega-3 fatty acids, but also in unhealthy PCB's.

Farmed salmon carry up to ten times as much cancer-causing chemicals as
their wild counterparts, according to a worldwide survey of fish destined
for supermarket shelves1.

The contaminants - a group of compounds called organochlorides - include a
family of industrial pollutants called polychlorinated biphenyls (PCBs). In
humans, these chemicals are linked to cancer and to developmental defects
such as stunted intelligence.

The findings deal a blow to salmon's perceived status as a healthy food,
says David Carpenter of the University at Albany in Rensselaer, New York, a
member of the study team. Salmon is rich in omega-3 fatty acids, which
protect against heart disease. But, says Carpenter, the presence of PCBs
means that people who have a low risk of heart problems might be advised to
steer clear.

The study estimates that, based on the US Environmental Protection Agency's
recommended maximum intake of organochlorides, Scottish consumers would be
advised to limit their salmon consumption to just six meals a year.

John Webster, scientific adviser to Scottish Quality Salmon, which
represents Scotland's salmon-farming industry, says that such extrapolations
are "scaremongering". "If we were to take that sort of advice we'd have
nothing on the menu at all," he says. Webster says that a similar analysis
by his group showed lower levels of contamination than Carpenter's team

Robert Lawrence, a public-health expert at Johns Hopkins University in
Baltimore, agrees that the risks of eating farmed salmon may outweigh the
benefits for some people. "It might be good for middle-aged men but not for
childbearing women and children," he says.

Vegetarian salmon

Carpenter and his colleagues purchased salmon from 16 cities in Europe and
North America. PCB levels in fish from the world's salmon-farming hotspots -
Europe, North America and Chile - were up to ten times those in wild-caught
salmon. Farms in Scotland and the nearby Faroe Islands were the worst

This is understandable given that Northern Europe has a long tradition of
industry, says Carpenter. PCBs are pumped out by the manufacture of
materials such as paints and flame-retardants, and by waste incineration.

Carpenter suspects that the pollutants find their way into the small fish
that are caught and processed into salmon feed. He suggests that farmers
consider making their salmon vegetarian, substituting soybeans or flaxseed
for fish protein, in order to reduce the problem.

If we were to take that sort of advice we'd have nothing on the menu at all

John Webster
Scottish Quality Salmon

Lawrence agrees that fish farms could benefit from a shake-up. He points out
that salmon in US farms are also fed recycled fat from slaughtered
agricultural animals such as cows. By feeding the salmon material from the
top of the food chain - which may already have high PCB levels - the problem
can be exacerbated.

Carpenter says that those striving for a healthy heart have other options.
Flaxseed oil, for example, is rich in omega-3 acids. "We're not telling
people not to eat fish," he says, "but there are alternative sources."


1. Hites, R. A. et al. Global assessment of organic contaminants
in farmed salmon. Science, 303, 226 - 229, (2004).

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