Laboratory tests performed by The New York Times at 20 Manhattan shops and restaurants found unacceptable levels of mercury, which might pose a health risk, the newspaper wrote on Wednesday.

The same newspaper said that a regular weekly diet of six pieces of tuna would exceed the maximum set by the Environmental Protection Agency.

“No one should eat a meal of tuna with mercury levels like those found in the restaurant samples more than about once every three week,” Michael Gochfeld, Professor of Environmental and Occupational Medicine at the Robert Wood Johnson Medical School, New Jersey, told the newspaper.

Professor Gochfel, who treats patients suffering from mercury poisoning, analyzed suhi made from bluefin tuna with Joanna Burger, a professor of life sciences at Rutgers University. The samples were taken from popular Manhattan restaurants Nobu Next Door, Sushi Seki, Sushi of Gary and Blue Ribbon Sushi and the grocery shop Gourmet Garage. They all had mercury above the “action level” of one part per million, at which the FDA can take food off the market.

Bluefin tuna is known for containing higher levels of mercury than other species of tuna such as yellowfin and albacore, because they have a longer life and accumulate more mercury in their body tissue. The problem is that persons who love suhi do not know what kind of suhi they get no matter they dine at the best restaurants or buy some suhi and have it home.

“I’m startled by this. Anything that might endanger any customer of ours, we’d be inclined to take off that menu immediately and get to the bottom of it,” Drew Nieporent, a managing partner of Nobu Next Door told the yesterday edition of The Times.

Following the tests, the owners of the restaurants said they would talk with their suppliers, who will also talk with their anglers.

According to recent studies, mercury may cause health problems for adults, including an increased risk of cardiovascular disease and neurological symptoms. Moreover, in 2004 the U.S. government warned women who were pregnant or might become pregnant and children to limit consumption of canned tuna because the mercury it contained could damage developing nervous systems.