WASHINGTON – The Environmental Protection Agency estimated in an internal report as much as $2 billion in yearly benefits from cutting mercury pollution just in the Southeast – 40 times the value the agency projected publicly for the entire nation.

Critics said the report is evidence the Bush administration sought to play down the benefits of reducing mercury pollution in order to justify not requiring owners of power plants to buy the best available technology for lowering mercury emissions.

“EPA has a track record of withholding information that doesn’t support their agenda, and this is the latest example,” said Felice Stadler, a policy specialist with the National Wildlife Federation.

The report, a copy of which was obtained last week by The Associated Press, dates to January 2004. That was 14 months before the EPA released its mercury rule for power plants.

Agency officials said the report is now subject to an internal peer review. They also said it was not taken into consideration for new regulations the agency issued in March to cut mercury pollution from power plants in half by 2020, from 48 tons a year now to 24.3 tons.

Environmental and health groups said that cleanup would go more quickly if the EPA had ordered the nation’s 600 coal-burning power plants to install hundreds of millions of dollars in new pollution controls and given them a firm deadline to do it.

Last month, the EPA publicly estimated the annual benefits to the country of the cleanup program at $50 million a year. The agency said the cost to utilities and electricity users would increase annually to $750 million a year by 2020.

The report studied the benefits of reducing mercury concentrations by 30 percent to 100 percent in marine fish and shellfish in the Southeast. It also identified an existing mercury “hot spot” – an area of accumulation – stretching across 50,000 square miles in the South Atlantic, roughly from North Carolina to South Florida.

That such a far-reaching mercury concentration exists raises questions about EPA officials’ public assertions that their new rule would prevent such hot spots. They also said the biggest health threat to people was from eating mercury-contaminated fish from abroad rather than those found in U.S. waters.

In March, while announcing the regulations, the EPA’s air quality chief, Jeffrey Holmstead, said, “We don’t think there will be any hot spots, we’re quite confident of that.”

Mercury concentrations accumulate in fish and work up the food chain. At greatest risk of nerve damage from the toxic metal are pregnant women, women of childbearing ages and young children.

The wildlife federation’s Stadler said the unreleased EPA report suggests mercury reductions could have a much broader impact than previously thought.

Forty percent of all mercury pollution in the United States comes from coal-fired power plants. But those emissions, 48 tons of mercury pollution a year, have never been regulated.

Jason Burnett, a policy adviser to air-quality chief Holmstead, said the report “was designed as a scoping study to help us identify areas for future research.”

The report said the mercury hot spot off the Atlantic coast was produced by “significant rainfall in the offshore area that washes out large amounts of mercury emitted by power plants and other sources.” It said pollution from U.S. sources is responsible for 37 percent to 68 percent of the mercury deposits there.

Burnett said the agency disagrees with that conclusion.

“The question is how much of that mercury comes from U.S. power plants, and that’s the quantification that we don’t believe is sufficiently understood to use in a rule-making context,” he said.

Environmentalists and administration critics have said that hot spots could be avoided if the EPA used the Clean Air Act to require individual power plants to install the most effective technology on the market for reducing mercury emissions from their stacks.