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New Research Predicts Pollutants In Farmed Salmon Based On Food They Eat

Amy Sisk
Carla Ng of the University of Pittsburgh draws the molecular structure of polybrominated diphenyl ethers, a chemical that sometimes makes its way into the feed of farmed salmon.

New research from the University of Pittsburgh provides a tool for examining pollutants in farmed salmon.

Carla Ng, an assistant professor in civil and environmental engineering, worked with Swiss researchers to look at the quality of water where salmon swim and the food they eat.

The researchers focused on toxic fire retardants found in old electronics, which are sometimes shipped overseas to places like China and Africa for recycling. When the plastics in the electronics are burned, they release the fire retardant chemical -- polybrominated diphenyl ethers -- into the air, Ng said.

The toxins settle on land or in the ocean, where they contaminate algae or phytoplankton. The pollutants make their way up the food chain, eventually into forage fish, which are ground up and processed into pellets fed to farmed salmon.

In high doses, the chemicals can pose health problems to humans, including developmental or liver problems, and possibly cancer, according to the Environmental Protection Agency.

Ng’s research is timely. Consumers are becoming increasingly cognizant of the origin of their food, she said.

“One thing that doesn’t necessarily come into the equation is where were the fish that my fish ate caught,” she said. “So this is a further step in the food chain, and it can be really important.”

Computer modeling developed by the researchers builds upon existing data to predict the level of pollutants in farmed salmon, depending on where they’re farmed and what they’re fed. It shows that raising a salmon in clean water does not guarantee the fish is low in contaminants, if it ate food containing the fire retardant chemicals.

In fact, contaminated feed is up to 1,000 times more important in determining concentrations of toxins in farmed salmon raised in clean water, compared to salmon who grew up in a heavily polluted environment, Ng said.

The researchers’ modeling may help the seafood industry ensure quality products, and it can be used to examine pollutants in other animal species, she said.

As for people who like to eat seafood, Ng said there’s no way to tell at the market whether a salmon fillet has toxic chemicals. She said a single serving doesn’t pose much of a health risk, but people who eat many servings of farmed salmon per week might want to pay attention.

“Don’t always eat the same fish from the same market of the same species, because if that happens to be a contaminated fish, you’d be getting the highest dose possible,” she said.

Ng conducted this research with Natalie von Goetz and Amélie Ritscher of the Swiss Federal Institute of Technology in Zurich, Switzerland.