The number of Superfund sites and the cost to clean them have been vastly overstated, the American Academy of Actuaries said in a report Wednesday.

External pressures on the Environmental Protection Agency, as well as cost shifting under the various reform proposals due to be introduced in Congress this month, should keep the number of new sites added to the National Priorities List (NPL) to under 50 a year, said the group.The total number of Superfund sites will be 2,000, rather than the 3,000 to

4,500 sites estimated by several groups, at a cost of less than $100 billion, instead of $150 billion to $165 billion, said the academy. The group's members are statisticians who predict insurer costs, including reserving for future losses.

Lower costs to Superfund mean lower taxes for chemical and petroleum companies and lower legal costs for their liability insurers.

Superfund expires in December. It was created in 1980 to clean up a few sites at a cost of $1 billion to $2 billion over five years, the report said. However, costs currently exceed $25 billion, and fewer than 220 of the 1,410 NPL sites have been cleaned.

The academy based its findings on information from, among others, the EPA, the Congressional Budget Office, the Chemical Manufacturers Association, the Office of Management and Budget and Superfund Reform '95, the umbrella organization representing insurers.

"In most areas, there is general agreement" among these organizations, said Raja Bhagavatula, who chaired the academy's Environmental Liabilities Work Group, which compiled the report. "But we question the large number of nonfederal NPL cleanup sites being assumed. If anything, budgetary and other pressures will keep the addition of new sites down."

The study also looked at a number of Superfund reform proposals that are either already before Congress or expected to be introduced later this month. Congress returned from its summer recess Tuesday.

The actuaries said the proposal favored by insurers, eliminating liability for legal dumping before 1987, would have a "substantial impact on private- sector costs and provide significant relief from the nearly $1 billion a year in legal costs."

That proposal would reduce legal costs by about $500 million and shift about $1.2 billion in cleanup costs from potentially responsible parties and their insurers to the government, said the report.

The 1987 liability cutoff is contained in legislation expected this month

from Rep. Mike Oxley, R-Ohio, chairman of the Commerce Committee's Subcommittee on Commerce, Trade and Hazardous Waste Materials, said Peggy Petersen, his press secretary. This bill has the support of the Republican leadership in the House and insurers.

A proposal that would end liability for pre-1980 dumping would shift $450 million in cleanup costs, the actuaries said. That plan is contained in a bill to be introduced this month by Sen. Robert Smith, R-N.H., chairman of the Senate Environment Committee's Superfund, Waste Control and Risk Assessment subcommittee.