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How safe is your tuna? It's important to know where it wascaught


Tuna caught inindustrialized areas of the Pacific and Atlantic oceans have 36 times morepollutants than those fished in remote parts of the West Pacific, scientistsfrom Scripps Oceanography have found.


The researcherstracked concentrations of toxins in tuna around the world and found that thelocation of fish, as much as its species, can affect how safe it is to eat.


“The pollutantlevels in seafood — and tuna in our case — can be heavily determined by thelocation where it was caught,” said lead author Sascha Nicklisch, apostdoctoral researcher at Scripps Institution of Oceanography at UC San Diego.“It is important to know the origin of catch of the fish, to know the amount ofpollutants in your fish.”


Researchers saidthey hoped the study would help advance understanding of how toxins enter ourfood supply through seafood and how to manage fisheries to reduce that risk.


The study,published in the June issue of the academic journal Environmental HealthPerspectives, tested tuna from locations around the globe for the presence ofpesticides, coolants and flame retardants. Together, they’re part of a class ofchemicals called persistent organic pollutants, which accumulate in body tissueand make their way up the food chain.


Big fish andpredators tend to have higher levels of toxic chemicals, so tuna offered a goodmeans of tracking them. And yellowfin, which are relatively large fish but haveshorter ranges than other tuna species, allowed researchers to look at regionalpollutants.


“They stay inthe location where they are born and hunt,” Nicklisch said. “So we tried to usethese tuna to create a snapshot of local contamination.”


Scientistsidentified eight key sites around the globe and analyzed 10 fish from each ofthem. To collect the samples, staff researcher Lindsay Bonito traveled fromTonga to Panama, Louisiana, Hawaii, Guam and Vietnam, chasing tuna.


“I was tasked togo out and actually secure tuna from all over the world,” Bonito said. “I wouldeither go out and fish for it, or contact fishermen.”


They screenedthe fish for 247 toxic compounds and calculated pollutant concentrations foreach area. Average toxin levels in tuna from the most polluted areas were 36times those found in the least polluted areas. The differences betweenindividual fish were even higher. Toxic levels in the most and least contaminatedtuna samples varied by a factor of 180, according to the report.


In general, Nicklisch said, the morecontaminated sites were industrialized areas of the northern hemisphere,including ocean regions off the Atlantic coast of Europe, and the east and westcoasts of North America. Those off of Asia, and in the Pacific Islands wererelatively clean, he said.


“The sites wherewe caught them are known to be more pristine, such as kingdom of Tonga,” hesaid.


Becausefood-born toxins can affect the health of people who eat them, the U.S.Environmental Protection Agency and Food and Drug Administration issueguidelines on how much fish to eat, with more protective recommendations forchildren and pregnant or nursing women.


Most of the tunaanalyzed in the study would be considered safe under current guidelines, theresearchers said. But there were wide variations between regions, and someareas, including the Gulf of Mexico and the Atlantic Ocean around Europe, hadhigh levels of unsafe fish.


In all of thetuna samples, researchers found a particularly pernicious set of chemicals.Each fish tested contained 10 specific compounds that interfere with proteinsthat regulate cell membranes and fend off toxins, Nicklisch said. By disablingthat defense, the toxic compounds open the floodgate to a host of otherpollutants.


“These compoundsmight lead to accumulation of chemicals in these tuna, because the proteinsusually block those compounds in fish, but also in us, in humans,” Nicklischsaid.


He said he hopedthe study would lead to better safety testing of chemicals found in food, andenhance public information and labeling of seafood.


“The mostimportant part of the take-home message is that it’s important to know whereyour fish was caught,” he said.