WASHINGTON — Some imports of canned tuna to
the United States have mercury levels higher than the federal limit, according
to analysis by an environmental group.
Defenders of Wildlife found the highest levels of mercury in tuna from Ecuador and Mexico -- countries known for setting nets where dolphins are seen to catch large tuna swimming below.
"They tend to catch larger, more mature fish, which tend to have higher levels, being at the top of the food chain," said Bob Irvin, the group's senior vice president for conservation.
The group is a longtime advocate of dolphin-safe tuna.
The group had a laboratory test 164 cans of tuna labeled as being from Ecuador, Mexico, Costa Rica, Thailand, Malaysia, the Philippines and the United States. Tests were done by New Age/Landmark laboratory, a Benton Harbor, Michigan, company that has been used by the federal government.
Analysis of the samples found:
--Average mercury content of U.S. tuna was generally lower than imported tuna.
--Tuna from Asia had the lowest average levels of mercury.
--Tuna from Latin America had the highest mercury levels, with some exceeding the government limit of 1.0 parts per million.
The lab found higher levels of mercury even in light tuna, which the Food and Drug Administration considers to be low in mercury.
The FDA says it is safe to eat two meals a week -- a total of 12 ounces (340 grams) -- of fish and shellfish that are lower in mercury, such as canned light tuna, shrimp, salmon, pollock and catfish.
Defenders of Wildlife said people should limit light tuna to one meal each week, instead of two, and avoid canned tuna that says it is imported from Latin America on the label.
"The occasional tuna sandwich is not going to cause any problems, but we are saying the government needs to do a better job of looking at mercury content in light canned tuna, which up to now has been touted as a low-mercury source of protein," Irvin said.
A food industry-backed group pointed out the government's 1.0 ppm limit has a tenfold safety cushion; it limits exposure to levels 10 times lower than what is thought to cause adverse effects.
"Without exception, every can of tuna sampled by Defenders of Wildlife is safe to eat," said David Martosko, research director for the Center for Consumer Freedom. "Fish is still brain food, and Americans should be eating more of it, not less."
About half the canned tuna in the United States is imported, the report said.
Mercury concentration levels above the federal limit were found in two samples of light tuna: Calmex from Mexico, which had 1.4 ppm, and Sardinar from Costa Rica, which had 1.3 ppm.
Above-the-limit concentrations were also found in four samples of Tuna Real brand solid pack tuna, which had levels as high as 1.5 ppm.
The federal government advises pregnant women, nursing mothers and young children to avoid fish with high levels of mercury -- shark, swordfish, king mackerel or tilefish. Elevated mercury levels have been linked to learning disabilities and developmental delays in children and to heart, nervous system and kidney damage in adults.
Traces of mercury are found in nearly all fish and shellfish. Released through industrial pollution, mercury falls and accumulates in streams and oceans as methylmercury. Methylmercury builds up in fish and shellfish as they feed, in some types more than others.
However, eating fish also has widely acknowledged health benefits. The American Heart Association advises people to eat fish at least twice a week.