Some 36 percent of swordfish, 33 percent of shark, and 4 percent of large tuna samples the FDA tested from 1992 to 1998 exceeded the level at which it is supposed to take action, according to the FDA's own data obtained under the Freedom of Information Act by the environmental groups. The information was released yesterday in a report by the Mercury Policy Project, Clean Water Action, the California Communities Against Toxics, and the Sierra Club.

The report also noted ''a disturbing trend to conduct less and less testing and to altogether cease monitoring for certain species.'' For instance, said the report, the agency tested 13 samples of canned tuna in 1995, and none in 1994, 1996, 1997, and 1998. On average, Americans consumed ten cans of tuna in 1998, the report said.

''It's totally outrageous,'' said Lee Ketelsen, New England director of Clean Water Action. ''It's the FDA's job to protect us from contaminants in food, and they've abandoned that when it comes to mercury in seafood.''

Mercury exists naturally in the environment, but is also used in thermometers and other products that end up in landfills and incinerators and is spewed by coal-fired power plants and other industrial sources. It gets converted to methyl mercury and climbs the food chain; it can threaten the health of people with existing neurological and developmental problems. A top FDA official acknowledged yesterday that sampling and testing have waned in recent years, but said that this was because the agency exhaustively sampled and tested in the 1970s, when mercury was a major concern. Its periodic testing since then has shown no major increase in the mercury threat, he said.

''What we're finding now, we found in the '70s,'' said Gregory Cramer, an FDA chemist in the agency's Office of Seafood. ''In fact, we're probably doing too good a job of scaring people away from fish, which may be causing even greater harm than mercury, because people are ignoring the health benefits of fish.''

Yet the environmental groups say that if mercury is a recognized problem in freshwater fish, with 40 states advising limits on fish consumption, especially for pregnant women and children, it should also be recognized as a problem in ocean fish.

The report notes that there has been a 25 percent increase in fish consumption since 1980, much of it in the form of large tuna sold as steaks or sushi. On average, Americans eat 19 pounds of fish a year, 15 pounds of which is from the sea, the report said.

Large ocean fish like swordfish, sharks, and tuna tend to have mercury in them despite the vast waters they roam in, which disperse pollution better than rivers and streams. That's because the fish are old and at the top of the food chain, gobbling up lots of smaller fish that may be riddled with mercury.

''It's like the federal government's `don't ask, don't tell' policy,'' said Michael Bender, the Mercury Policy Project's director, noting the report's finding that the FDA is not monitoring swordfish, shark, and tuna from domestic waters any longer, and is inadequately monitoring those species from international waters. ''If the FDA doesn't look for problems, then it can't honestly tell anyone there are problems.''

Cramer of the FDA said that the National Academy of Sciences is reviewing the FDA action level of 1 part per million of mercury in seafood and will issue a recommendation this summer on whether to change it. But barring that, the FDA ''is comfortable'' with the current standard.

But two Democratic senators on Capitol Hill remain unconvinced. Vermont Senator Patrick Leahy and Iowa Senator Tom Harkin blasted the FDA yesterday for its ''troubling'' response to concerns they raised about the agency's handling of the mercury threat in a congressional inquiry last October.

''The FDA response to our inquiry confirms our worst fears,'' Leahy said. ''FDA stopped monitoring mercury levels in domestically caught swordfish, shark, and tuna in 1998. Yet in one sampling, three of the four fish tested in 1997 had levels exceeding FDA's human health standard for mercury.''

© Copyright 2000 Globe Newspaper Company.

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