Lo­ca­tion is key fac­tor in tox­i­c­ity of f ish

Ex­perts search the world and con­clude lo­ca­tion of­fers clues to pol­lu­tant lev­els.

Los Angeles Times - - CALIFORNIA - DEB­O­RAH SUL­LI­VAN BRENNAN deb­o­rah.brennan@sdunion­tri­bune.com Brennan writes for the San Diego Union-Tri­bune.

Tuna caught in in­dus­tri­al­ized ar­eas have more pol­lu­tants than those fished in re­mote wa­ters.

SAN DIEGO — Tuna caught in in­dus­tri­al­ized ar­eas of the Pa­cific and At­lantic oceans have 36 times more pol­lu­tants than those fished in re­mote parts of the West Pa­cific, sci­en­tists from Scripps Oceanog­ra­phy have found.

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

“The pol­lu­tant lev­els in seafood — and tuna in our case — can be heav­ily de­ter­mined by the lo­ca­tion where it was caught,” said lead au­thor Sascha Nick­lisch, a post­doc­toral 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 of pol­lu­tants in your fish.”

Re­searchers said they hoped the study would help ad­vance un­der­stand­ing of how tox­ins en­ter our food sup­ply through seafood and how to man­age fish­eries to re­duce that risk.

The study, pub­lished in the June is­sue of En­vi­ron­men­tal Health Per­spec­tives, tested tuna for the pres­ence of pes­ti­cides, coolants and flame re­tar­dants. To­gether, they’re part of a class of chem­i­cals called per­sis­tent or­ganic pol­lu­tants, which ac­cu­mu­late in body tis­sue and make their way up the food chain.

Big fish and preda­tors tend to have higher lev­els of toxic chem­i­cals, so tuna of­fered a good means of track­ing them. And yel­lowfin, which are rel­a­tively large fish but have shorter ranges than other tuna species, al­lowed re­searchers to study re­gional pol­lu­tants.

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

Sci­en­tists iden­ti­fied eight key sites and an­a­lyzed 10 fish from each of them. To col­lect the sam­ples, staff re­searcher Lind­say Bonito trav­eled from Tonga to Panama, Louisiana, Hawaii, Guam and Viet­nam.

They screened the fish for 247 toxic com­pounds and cal­cu­lated pol­lu­tant con­cen­tra­tions for each area. Av­er­age toxin lev­els in tuna from the most pol­luted ar­eas were 36 times those found in the least pol­luted ar­eas. The dif­fer­ences be­tween in­di­vid­ual fish were even higher. Toxic lev­els in the most and least con­tam­i­nated sam­ples var­ied by a fac­tor of 180, the re­port said.

In gen­eral, Nick­lisch said, the more con­tam­i­nated sites were in­dus­tri­al­ized ar­eas of the North­ern Hemi­sphere, in­clud­ing ocean re­gions off the At­lantic Coast of Europe, and the East and West coasts of North Amer­ica. Those off Asia and in the Pa­cific Is­lands were rel­a­tively clean, he said.

Some of the sites, such as the king­dom of Tonga, are known to be more pris­tine, he said.

Be­cause food-borne tox­ins can af­fect the health of peo­ple who eat them, the U.S. En­vi­ron­men­tal Pro­tec­tion Agency and Food and Drug Ad­min­is­tra­tion is­sue guide­lines on how much fish to eat, with more pro­tec­tive rec­om­men­da­tions for chil­dren and preg­nant or nurs­ing women.

Most of the tuna an­a­lyzed in the study would be con­sid­ered safe un­der cur­rent guide­lines, the re­searchers said. But there were wide vari­a­tions be­tween re­gions, and some ar­eas, in­clud­ing the Gulf of Mex­ico and the At­lantic Ocean around Europe, had high lev­els of un­safe fish.

In all of the tuna sam­ples, re­searchers found a par­tic­u­larly per­ni­cious set of chem­i­cals.

Each fish tested con­tained 10 spe­cific com­pounds that in­ter­fere with pro­teins that reg­u­late cell mem­branes and fend off tox­ins, Nick­lisch said. By dis­abling that de­fense, the toxic com­pounds open the flood­gate to a host of other pol­lu­tants.

“These com­pounds might lead to ac­cu­mu­la­tion of chem­i­cals in these tuna, be­cause the pro­teins usu­ally block those com­pounds in fish, but also in us, in hu­mans,” Nick­lisch said.

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

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

Axel Koester For The Times

T U NA caught in in­dus­tri­al­ized ar­eas of the At­lantic and Pa­cific oceans were found to have 36 times more pol­lu­tants than those in the cleaner Pa­cific Is­lands.

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