Defenders of Wildlife, an environmental group that advocates dolphin-safe tuna, ran a Michigan laboratory test on nearly 200 cans of tuna imported from Ecuador, Mexico, Costa Rica, Thailand, Malaysia and the Philippines, as well tuna from the United States.
The lab results revealed that tuna from Asian countries contained the lowest levels of mercury, while tuna from Latin American countries had the highest levels. Some Latin American tuna exceeded the U.S. government's mercury limit of 1.0 parts per million. The U.S. tuna contained less mercury than the imports.
The FDA says it is safe to eat two weekly meals of low-mercury fish and shellfish, such as salmon, catfish and light tuna. However, the agency recommends limiting consumption of white albacore tuna, which has higher levels of mercury.
Defenders of Wildlife says that in light of its recent research, people should limit their consumption of light tuna to just one meal per week. "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," says Bob Irvin, senior vice president for conservation at Defenders of Wildlife.
Elevated levels of mercury have been linked to developmental and learning disabilities in children, as well as kidney, heart and nervous system damage in adults. The U.S. government recommends that pregnant or nursing women and young children avoid fish high in mercury.
Mercury finds its way to the oceans due to emissions from coal power plants, runoff from mining operations, industrial waste and even consumer products like batteries.