Would you like some tuna with that mercury?

Some months ago we reported on a new study that found high mercury levels in blood samples from New Yorkers who eat a lot of fish—particularly affluent consumers, who presumably eat more expensive high-mercury varieties like tuna and swordfish. In January, results of new tests commissioned by The New York Times showed how concentrated mercury has become in one of the most popular kinds of sushi.

The newspaper purchased tuna sushi samples from 20 restaurants and stores in New York City and tested them for mercury. Levels detected in some samples  exceeded the Food and Drug Administration's action level of 1 part per million, a threshold for which the FDA can remove fish from sale. The Times then calculated how many pieces of sushi it would take to deliver a dose of mercury greater than what the federal government considers acceptable. Those numbers ranged from 2 to 10 for restaurant sushi and 4 to 72 for gourmet/grocery story sushi. In general, the samples from restaurants showed higher levels of mercury than those from markets.

Expensive grades of tuna tend to come from larger, older fish that are more prone to accumulating high levels of mercury. Mercury exposure from fish has been linked to a range of neurological and developmental damage in young children as well as cardiovascular disease in adults. So sushi-lovers, particularly women of childbearing age should get to know the fish in their favorite selections and choose pieces known to be lowest in mercury. To learn which species have been found in past FDA tests to carry the lowest levels of mercury, see our June 2006 story on mercury in tuna.

Unfortunately, the FDA does not routinely test seafood for mercury, or fish used specifically for sushi, which could be different from fish fillets sold in the store.

Consumers Union has long advocated for stricter standards for mercury in fish and stronger consumption advice for consumers, which FDA officials say they are in the process of reviewing.  Hopefully they won’t rely on the fish industry to craft their policies, as some other organizations have in recent months.

Related reporting

• More testing of tuna to address mercury concerns (NY Times)
• Taking worry off the plate (NY Times)
• Making sense out of mercury in fish (NPR)