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Serve up sushi ... with a side of mercury?

Studies suggest metal levels in tuna may be higher than deemed safe by the FDA. TODAY Food editor Phil Lempert shares his food safety alert.
/ Source: TODAY contributor

New concerns were raised over the past couple of weeks about the content of mercury in fish, suggesting that updates are needed for the 2004 FDA’s consumer advisory guidelines regarding fish safety. The studies, which looked at the mercury content of fish samples purchased at both sushi restaurants and grocery stores, found that a large percentage of the samples contained levels of mercury beyond those that the FDA considers safe.

Since last week's recall of 134 million pounds of ground beef, consumers, retailers and legislators are voicing their concerns about just how competent the FDA and USDA’s testing for food safety really is. And I have little doubt that as a result of last year’s food recalls (which numbered over 975), other nongovernmental groups are stepping up to the plate.

For example, Oceana, a marine conservation group, recently did a fish study of their own. They looked at swordfish, fresh tuna and tilapia samples purchased in 26 different cities across the country, as well as samples of nigiri or sashimi-style tuna and mackerel purchased from 23 different U.S. cities. While tilapia from grocery stores and mackerel in sushi restaurants checked out as good, low-mercury alternatives, tuna and swordfish results were found to have considerably less favorable results.

Oceana found that the mercury levels in tuna were much higher than existing FDA data suggests, with one-third of sushi tuna samples exceeding one part per million — the action level allowed by the FDA for fish intended for human consumption. Additionally, they found that two-thirds of swordfish tested were above the one-part-per-million mark.

Another study conducted for the New York Times with Rutgers University had similar findings. Their study looked at sushi from 20 Manhattan stores and restaurants. Tuna samples from five of the 20 restaurants contained mercury levels above one part per million, with the highest mercury concentration, at 1.4 parts per million, found in one particular restaurant.

Grocery-store mercury levels in fish tended to be lower than levels of mercury in fish from sushi restaurants in the New York Times study — a finding confirmed by the Oceana study as well. Even so, the average mercury concentration for grocery-store tuna, per the Oceana study, was .68 parts per million — nearly double the FDA’s average finding of .38 parts per million for fresh or frozen tuna.

Mercury is a metal released into the environment. About two-thirds of mercury in the environment comes from human sources; only about one-third of it is naturally occurring. The primary industrial (human) source of mercury enters the environment through the burning of fossil fuels, especially coal. It also comes from intentional uses of mercury, such as its use in the production of chlorine and mercury-containing devices such as thermostats. Municipal waste incineration is another source.

When mercury finds its way into rivers and lakes, small fish take it up when eating algae. The ingested mercury gets biomagnified as it moves up the food chain. Larger predatory fish eat smaller fish that have eaten even smaller fish, and so on. These larger fish, like sharks and swordfish, tend to contain higher levels of mercury, but nearly all fish and shellfish contain trace amounts of the metal. Mercury can damage the organs of the central nervous system and cardiovascular systems when consumed at high levels.

Tuna is the No. 1 source of mercury in the American diet, according to Oceana, due largely to high levels of tuna consumption. Consumption of sushi tuna and tuna steaks has peaked in popularity in recent years, as compared to consumption of the less glamorous canned light tuna — a variety that is considerably lower in mercury content. The Oceana study found that average mercury levels in sushi tuna exceeded levels in king mackerel, a fish on the FDA’s “Do Not Eat” list. Currently, tuna is not on this list.

The current EPA and FDA consumer advisory, published in 2004, recommends that women of childbearing age and young children avoid eating swordfish, shark, tilefish and king mackerel. The advisory also recommends limiting the consumption of albacore tuna or tuna steaks to six ounces or less per week, while limiting other low-mercury fish to 12 ounces or less per week.

A good rule of thumb is, the larger and older the fish, the more mercury and toxins it will contain.

For a complete FDA list of mercury levels in fish and shellfish, visit: www.cfsan.fda.gov/~frf/sea-mehg.html

For a list of fish considered safe to eat, and sustainably raised, visit:www.oceana.org/fileadmin/oceana/uploads/marketing/Web_color_seafood_guide.pdf

Phil Lempert is food editor of the TODAY show. He welcomes questions and comments, which can be sent to . For more about the latest trends on the supermarket shelves, visit Phil’s Web site at .