Canned Tuna May Contain Excessive Mercury
Canned albacore tuna purchased by U.S. schools contains more mercury than what government officials have reported, raising the risks for some tuna-loving kids, according to a new study from a coalition of advocacy groups.
Children who eat two medium servings of albacore, or white, tuna per week could be exposed to as much as six times the dose that federal guidelines consider safe, according to the report prepared for the Mercury Policy Project. It is the first study to test the mercury content of tuna brands purchased by schools.
The report recommends that all children avoid eating albacore tuna. The report recommends that all children less than 55 pounds eat "light" fish only once per month and children above this weight eat it twice per year.
In 2004, both the U.S. Food and Drug Administration and Environmental Protection Agency recommended that canned white tuna be limited to six ounces per week for pregnant and nursing mothers, as well as women who are likely to become pregnant and children. The government suggests that light tuna, which is made from skipjack species, contains less mercury and should be limited to 12 ounces each week.
But the advocates say those recommendations are too lax because their tests show that "customers who choose canned albacore tuna may fairly frequently get mercury levels more than twice the FDA's average for the species," the report says.
The mercury content of light tuna was, however, slightly less than FDA testing have indicated.
The FDA representatives and representatives from tuna companies could not be reached for comment.
Mercury, a neurotoxin found in fish and especially larger species like albacore tuna, builds up.
Because canned tuna is a cheap, nutritional food that is popular in schools, parents should rotate other fish into their children's diet to reduce their risk of neurological effects, the report suggests.
"Most kids don't eat that much tuna, so nothing really is needed to modify the behavior of a majority of kids," said Ned Groth, co-author of the report and former senior scientist at the Consumers Union. "Kids that consume more than 90% of the tuna are where my focus would be."
Scientists not involved with the study generally agreed with the report's advice.
"They are probably good, conservative recommendations," said University of South Carolina assistant professor Jennifer Nyland, who studies mercury's effects on autoimmune diseases.
Over a decade ago, a panel of National Research Council scientists found that children who were exposed to mercury in their prenatal period have lower mental skills. The FDA and EPA fish consumption guidelines are based on 25 years of studies of effects in Faroe Islands children highly exposed to mercury in the womb.
The health of children who consume tuna is unknown. However, it's not known if there are any risks to pregnant women eating tuna. Industry associations argue that children have eaten tuna fish sandwiches for many years without any apparent harm.
Groth stated that no one can say for sure what the effect on children is, as nobody has looked. It's reasonable to suppose that children are susceptible to methylmercury poisoning. However, there is no epidemiological evidence at this time.
These recommendations are more strict than what experts recommend for children's light tuna consumption. They wanted to limit mercury exposure to children within 25% of the EPA recommended safe dose. However, the EPA has already built a 10-fold safety margin into this dose. Groth agreed that it was a reasonable goal, given the uncertainty in science about the dangers to children.
11. Samples of canned albacore tuna were found to have mercury levels of 0.560 micrograms per gram. The average reported by FDA this year is 0.350 micrograms per gram. The sample size is small, but three out of the 11 cans had mercury levels more than twice the average values reported by the FDA.
Average mercury levels in 48 "light" samples of tuna were roughly the same as those in white tuna.
The report adds to other research showing that albacore has more mercury than FDA tests have revealed.
"The main value of this study is that it points out that because tuna, especially white, or albacore, can be moderate-to-high in mercury - and because canned tuna is so popular in our diets - that mercury exposure from canned tuna is of concern," said Roxanne Karimi, a marine scientist at Stony Brook University who was not involved with the study. Karimi's research also has shown that mercury levels in fish vary widely from what the FDA reports.
The new study examined the mercury concentrations in 35 large (66.5 oz) cans and 24 large (43 oz) foil pouches from brand lines and products sold specifically to schools. Sunkist and Chicken of the Sea made up 60% of the light tuna tested.
50 of the 59 samples of tuna were brought to America. Nine samples of U.S.-caught Tuna were the ones with the highest mercury levels. It was the Ecuadorian "Light" species that had the highest average mercury content.
In the study, tuna mercury levels were highly variable between samples, which means parents or schools can't easily judge its safety, Groth said. The report suggests that schools should avoid buying tuna from Ecuador and other Latin American countries, instead buying U.S. or Asian tuna.
Groth stated that the main message to parents is not that children should stop eating tuna. He said, "Stop focusing on children who consume too much tuna. Give them other types of healthy seafood." Don't give up on tuna. Most children can eat it.
The report was co-sponsored by nine other advocacy groups, including Physicians for Social Responsibility and the Center for Science in the Public Interest.