Why do tuna have mercury in them

Mercury comes from both natural sources — like volcanoes — as well as man-made sources like air pollution from power plants and other industrial sources that burn fossil fuels. Once it enters the atmosphere, mercury rains down on rivers, lakes and oceans, where it then enters the food web.

There are two main kinds of canned tuna : chunk light and solid or chunk white albacore. All canned white tuna is albacore. Its mercury levels are almost three times higher than the smaller skipjack tuna, used in most canned light tuna products. Tests on some students' hair furthered indicated mercury levels that were above what is considered "a level of concern".

In more serious cases, mercury poisoning can cause high blood pressure, low cognitive function, blindness, and lung and kidney dysfunction. For pregnant people, the dangers can be even more acute. As with all things in life, then, moderation is key.

Follow Gavin on Twitter or Instagram. Sign In Create Account. It's the go-to "healthy" meal for uni students and gym bros alike. But how much tuna is too much? And how real is the risk of mercury toxicity? July 10, , am.

The U. In partnership with the U. Food and Drug Administration, the EPA issues determinations periodically in regard to how much mercury is safe for consumers to ingest from eating fish. The EPA consolidates these local and regional advisories on its website, where concerned consumers and fisher folk can click on a map of the states to find out which advisories may be in effect in their area.

As for which fish to avoid, the non-profit Environmental Defense Fund EDF , which runs the handy Seafood Selector website, reports that people with mercury concerns should steer clear of bluefin tuna, walleye, king mackerel and marlin. Bluefish, shark, swordfish, wild sturgeon, opah and bigeye tuna carry a proportionately large mercury burden as well.

Also of concern, but to a slightly lesser extent, are orange roughy, Chilean sea bass, blue crab, lingcod, Spanish mackerel, spotted seatrout, wahoo, grouper, snapper, halibut, tile fish, rock fish and sable fish, as well as blackfin, albacore and yellowfin tuna.

Beyond what individuals can do to avoid mercury, the U. The agreement commits signatory countries—including the U. A legally binding treaty mandating just how much each country will have to cut back mercury emissions takes hold in Send questions to : earthtalk emagazine.