- Mar 10, 2018 -
Where does mercury come from?
Air pollution. Specifically, it rains down on rivers, lakes and oceans after being emitted from power plants and other industrial sources that burn fossil fuels.
Mercury in canned tuna
New tests reinforce a need for some people to limit consumption
Canned tuna, Americans’ favorite fish, is the most common source of mercury in our diet. New tests of 42 samples from cans and pouches of tuna bought primarily in the New York metropolitan area and online confirm that white (albacore) tuna usually contains far more mercury than light tuna.
Children and women of childbearing age can easily consume more mercury than the Environmental Protection Agency considers advisable simply by eating one serving of canned white tuna or two servings of light tuna per week. A serving is about 2.5 ounces. Expect a 5-ounce can to contain about 4 ounces of tuna plus liquid.
The heavy metal accumulates in tuna and other fish in an especially toxic form, methylmercury, which comes from mercury released by coal-fired power plants and other industrial or natural sources, such as volcanoes.
Fortunately, it’s easy to choose lower-mercury fish that are also rich in healthful omega-3 fatty acids. That’s especially important for women who are pregnant or might become pregnant, nursing mothers, and young children, because fetuses and youngsters seem to face the most risk from methylmercury’s neurotoxic effects.
Results from our tuna tests, conducted at an outside lab, underscore the longheld concern for those people. We found:
Every sample contained measurable levels of mercury, ranging from 0.018 to 0.774 parts per million. The Food and Drug Administration can take legal action to pull products containing 1 ppm or more from the market. (It never has, according to an FDA spokesman.) The EPA compiles fish advisories when state and local governments have found high contaminant levels in certain locally caught fish.
Samples of white tuna had 0.217 to 0.774 ppm of mercury and averaged 0.427 ppm. By eating 2.5 ounces of any of the tested samples, a woman of childbearing age would exceed the daily mercury intake that the EPA considers safe.
Samples of light tuna had 0.018 to 0.176 ppm and averaged 0.071 ppm. At that average, a woman of childbearing age eating 2.5 ounces would get less than the EPA’s limit, but for about half the tested samples, eating 5 ounces would exceed the limit.