Many samples of tuna sushi purchased in New York City in October 2007 contained dangerous levels of mercury, according to an investigative report by Marian Burros in today's New York Times. The levels, caused mainly by industrial pollution, were especially alarming for tuna sold in high-end restaurants, such as Blue Ribbon Sushi, which are thought to make tuna sushi from larger (older) bluefin tuna rather than smaller albacore and yellowfin tuna, which tend to contain less mercury.
Some article excerpts:
Recent laboratory tests found so much mercury in tuna sushi from 20 Manhattan stores and restaurants that at most of them, a regular diet of six pieces a week would exceed the levels considered acceptable by the Environmental Protection Agency.An interesting aspect of the New York Times report is that it is accompanied by a chart that analyzes the mercury content in terms of parts per million (ppm) as well as serving sizes. Examining the chart, you can see that an ordinary difference in serving size can make a restaurant portion with a relatively low ppm more dangerous than a restaurant portion with a relatively high ppm. This might (or might not) point to a weakness in FDA labeling proposals that seem to define gluten levels only by ppm, not by serving size.
Sushi from 5 of the 20 places had mercury levels so high that the Food and Drug Administration could take legal action to remove the fish from the market.
"No one should eat a meal of tuna with mercury levels like those found in the restaurant samples more than about once every three weeks," said Dr. Michael Gochfeld, professor of environmental and occupational medicine at the Robert Wood Johnson Medical School in Piscataway, N.J.
The owner of a restaurant whose tuna sushi had particularly high mercury concentrations said he was shocked by the findings. "I’m startled by this," said the owner, Drew Nieporent, a managing partner of Nobu Next Door. "Anything that might endanger any customer of ours, we’d be inclined to take off the menu immediately and get to the bottom of it."
Although the samples were gathered in New York City, experts believe similar results would be observed elsewhere.
In 2004 the Food and Drug Administration joined with the Environmental Protection Agency to warn women who might become pregnant and children to limit their consumption of certain varieties of canned tuna because the mercury it contained might damage the developing nervous system. Fresh tuna was not included in the advisory. Most of the tuna sushi in the Times samples contained far more mercury than is typically found in canned tuna.
Over the past several years, studies have suggested that mercury may also cause health problems for adults, including an increased risk of cardiovascular disease and neurological symptoms.
No government agency regularly tests seafood for mercury.
Tuna samples from the Manhattan restaurants Nobu Next Door, Sushi Seki, Sushi of Gari and Blue Ribbon Sushi and the food store Gourmet Garage all had mercury above one part per million, the "action level" at which the F.D.A. can take food off the market. (The F.D.A. has rarely, if ever, taken any tuna off the market.) The highest mercury concentration, 1.4 parts per million, was found in tuna from Blue Ribbon Sushi. The lowest, 0.10, was bought at Fairway.
At Blue Ribbon Sushi, Eric Bromberg, an owner, said he was aware that bluefin tuna had higher mercury concentrations. For that reason, Mr. Bromberg said, the restaurant typically told parents with small children not to let them eat "more than one or two pieces."
Six pieces of sushi from most of the restaurants and stores would contain more than 49 micrograms of mercury. That is the amount the Environmental Protection Agency deems acceptable for weekly consumption over a period of several months by an adult of average weight, which the agency defines as 154 pounds.
According to a 2007 survey by the New York City Department of Health and Mental Hygiene, the average level of mercury in New Yorkers’ blood is three times higher than the national average. The report found especially high levels among Asian New Yorkers, especially foreign-born Chinese, and people with high incomes. The report noted that Asians tend to eat more seafood, and it speculated that wealthier people favored fish, like swordfish and bluefin tuna, that happen to have higher mercury levels.
The city has warned women who are pregnant or breast-feeding and children not to eat fresh tuna, Chilean sea bass, swordfish, shark, grouper and other kinds of fish it describes as "too high in mercury." (Cooking fish has no effect on the mercury level.)
The news about high levels of mercury in sushi tuna comes at a time when Michael Bloomberg's city government seems to be focused largely on implementing strict restaurant inspections and getting fast food restaurants to disclose the calorie content of their foods. This is part of a trend: Other states and cities are considering legislating the disclosure of nutritional information on menus, too.
It seems to me that inspections of food quality at restaurants should include measures such as the sampling of fish for mercury levels, with follow-up actions consistent with health warnings from parties such as the FDA and the city's Department of Health and Mental Hygiene. Similar practices might also be warranted regarding issues such as the gluten or allergen content of foods. As I've suggested previously, something is lacking when most of an estimated 1% of the population might be "poisoned" by gluten in food but doesn't realize it, while governments have not established food preparer standards for good practices regarding gluten and allergens.
Here is a video about mercury contamination from the environmental group Oceana. Note that symptoms of mercury poisoning are similar to non-intestinal symptoms experienced by many people who have celiac disease. Medical testing is a good way to investigate the cause of symptoms in any particular case.