Kids heading back to school this month are finding healthier options in the lunchroom, thanks to new federal rules that require more fruits and vegetables, less sodium and fat and fewer calories in public-school lunches.
But a report released last week points to one area of potential risk that hasn't received much attention: the presence of mercury in tuna fish served in school lunches.
When mercury is released into the environment, it eventually makes its way into the water supply, and then into fishes' diets. The toxin accumulates at especially high levels in the bodies of larger and longer-lived predatory fish, including shark, swordfish and that lunchtime staple, tuna. When humans eat fish with high mercury levels, it can adversely affect brain development as well as the immune and nervous systems. Children are at particularly high risk.
The report—called, aptly, "Tuna Surprise"—was released by the Vermont-based Mercury Policy Project in conjunction with several other environmental and public health nonprofits, including the Vermont Public Interest Research Group and Mass. Clean Water Action. It looked at 59 samples of tuna sold to schools in 11 states, including Massachusetts. (The group declined to identify specific school districts, citing liability concerns.)
The results were mixed; in some cases, the samples tested actually had lower methylmercury levels than the levels found by other researchers in tuna sold in supermarkets. In other cases, the levels were significantly higher—specifically, in albacore tuna, which generally has higher levels than light tuna.
According to the report, new research indicates that mercury poses risks at lower levels than previously believed. And the risks, it adds, vary depending on several factors, including a child's weight, the kind of tuna and the serving size. "There is no 'bright line' between 'safe' and 'unsafe' exposures, and risk is generally proportional to dose," the researchers wrote.
To reduce children's risk, the report recommends that children eat no albacore tuna, which was found to have triple the mercury content of light tuna. It also recommends limiting exposure to light tuna, suggesting that smaller children (those weighing less than 55 pounds) eat it no more than once a month and bigger children no more than twice a month. Children who tend to consume a lot of tuna should have their blood tested for mercury.
"Most children are already consuming only modest amounts of tuna and are not at significant risk," Michael Bender, the Mercury Policy Project director, said in a release. "So the focus really needs to be on kids who eat tuna often, to limit their mercury exposure by offering them lower-mercury seafood or other nutritious alternatives."
The report also calls on the federal government to stop subsidizing tuna in school lunch programs and instead phase in seafood with lower levels of mercury, such as salmon and shrimp. "Canned tuna is overwhelmingly the largest source of U.S. children's methylmercury exposure, and some children's overall mercury dose is clearly high enough to raise substantial risk concerns," the study says. "There is no sound reason why taxpayer dollars should be used to subsidize any part of this risk."
In addition, the groups behind the report support efforts to stop mercury from being released into the environment—and, eventually, finding its way into the fish we eat—in the first place. That includes, in Massachusetts, campaigns to reduce mercury emissions from coal-fired power plants and incinerators and to require recycling programs for old thermostats that contain mercury.
"It's unfortunate that this otherwise healthy food is contaminated with toxic mercury and that parents and schools need to keep it from appearing too frequently on the menu," Elizabeth Saunders, legislative director for Mass. Clean Water Action, said in an announcement of the report. "The good news is that there is a solution to this problem, if only our state's leaders can find the political will. Keeping mercury-containing products out of the trash and transitioning to cleaner energy sources will get us closer to putting a stop to mercury pollution and making tuna fish safe to eat again."