WASHINGTON — One of every three lakes in the United States and nearly one-quarter of its rivers contain enough pollution that people should limit or avoid eating fish caught in them.

Every state but Alaska and Wyoming issued fish advisories covering some and occasionally all of their lakes or rivers in 2003, said a national database maintained by the Environmental Protection Agency and updated every year.

Though the number of advisories rose to 3,094, up from 2,814 in 2002, figures released Tuesday showed, EPA Administrator Mike Leavitt said the increase was due to more monitoring, not more pollution.

Nearly all the advisories involve contaminants such as mercury, dioxins, PCBs, pesticides and heavy metals, including arsenic, copper and lead. Currently they cover 35 per cent of the lakes and 24 per cent of rivers.

Leavitt said mercury pollution from industry is decreasing, though he cited figures only as recent as five years ago.

Primary sources of mercury pollution include coal-burning power plants, the burning of hazardous and medical waste and production of chlorine. It also occurs naturally in the environment.

The advisories cover fish caught during recreational and sport fishing, not deep-sea commercial fishing or fish-farming operations.

"It's about trout, not tuna. It's about what you catch on the shore, not what you buy on the shelf," Leavitt said.

"This is about the health of pregnant mothers and small children, that's the primary focus of our concern."

But he also acknowledged virtually every hectare of lakes and kilometre of rivers could eventually be covered by advisories.

Since pollution is found in fish nearly every time a state looks for it, the EPA assumes whenever a state does that kind of monitoring it will wind up issuing a fish advisory, he said.

"I want to make clear that this agency views mercury as a toxin. Manmade emissions need to be reduced and regulated. There has been an appropriate, heightened public concern," Leavitt said.

This year, 44 states had a fish advisory for mercury, a persistent substance that affects the nervous system. Two more states, Montana and Washington, added statewide advisories to warn of the potential for widespread contamination of fish.

Servings of fish caught by family or friends and not covered by an advisory should be limited to one 170-gram portion a week, the FDA said.

The latest figures troubled frequent critics of the U.S. administration, including environmentalist groups such as the Sierra Club, the National Wildlife Federation and Natural Resources Defense Council. They want stricter limits imposed on mercury pollution from coal-fired power plants.

Earlier this month, an environmental advocacy coalition released a report citing EPA figures to claim 76 per cent of fish samples collected from 260 bodies of water exceeded the agency's mercury exposure limits for children under three.

"Sadly, America's women and children are paying for the administration's procrastination," said Carl Pope, executive director of the Sierra Club, which noted state advisories now cover 5.3 million hectares of lakes and 1.2 million kilometres of rivers.

"This listing clearly indicates that we are moving in the wrong direction on mercury pollution," said Senator Jim Jeffords of Vermont, a senior member of the Senate environment and public works committee.

Jeffords and President George W. Bush have each proposed ways of regulating mercury and other pollution from coal-fired power plants. Jeffords would have the government force industry to reduce mercury emissions by 90 per cent by 2008; Bush wants to cut mercury emissions by 70 per cent by 2018.

The EPA, after being sued by NRDC, plans to issue by mid-March the first regulations for the 43 tonnes of mercury a year from power plants.