A separate EPA-commissioned study released in February by the Harvard Center for Risk Analysis estimated that there could be $5 billion a year in public health benefits from a 62.5 percent cut in the mercury released by power plants. That study too was excluded from consideration in the rule EPA set in March.
The report on Southeast benefits, a copy of which was obtained by the Associated Press, looked at reducing mercury concentrations in marine fish and shellfish.
It did not estimate the cost of achieving this reduction but said reducing national mercury emissions by 30 percent to 100 percent would produce Southeast benefits of between $600 million to more than $2 billion.
This report also found a mercury ''hot spot" -- deposits of the toxic metal stretching across 50,000 square miles in the South Atlantic, from North Carolina to South Florida.
The large mercury concentration raises questions about public assertions by EPA officials that the new rule would prevent such hot spots.
Announcing that regulation in March, EPA air quality chief Jeffrey Holmstead said: ''We don't think there will be any hot spots. We're quite confident of that."
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 US pollution is responsible for 37 percent to 68 percent of the mercury deposits there.
Jason Burnett, a policy aide to Holmstead, said Thursday that his agency disagrees with the conclusion.
''The question is how much of that mercury comes from US power plants, and that's the quantification that we don't believe is sufficiently understood to use in a rule-making context," he said.
Douglas Rae, a Boston economist and principal author of the internal report, said the EPA commissioned it two years ago. ''I think it's reasonable, but people can argue about that," he said in an interview Thursday.
Rae said it is ''the kind of analysis that EPA staff do all the time. They don't intend them to be used in a rule-making because there are a lot of uncertainties."
