The Manassas International Business Machines plant has been named by the U.S. Environmental Protection Agency as a "long-term, chronic threat to the public health," but state and local authorities and corporate officials said the designation is unfair.

The plant was part of an EPA list of 244 "priority sites" across the country to be covered by the $1.6 billion "Superfund" hazardous waste clean-up program.

The agency said that in the early 1970s, spills of an organic cleansing solvent, a suspected carcinogen, had contaminated groundwater in the area and posed a threat to 32,000 people living within three miles of the site.

IBM notified the EPA in 1982 for the first time of tests that had detected the solvents in an aquifer that provides drinking water at the plant site, according to W. Jerrold Samford, chief geologist for Virginia's Water Control Board's northern regional office.

However, state and county environmental officials say that IBM has the threat under control, and that they were surprised the plant was on the EPA list.

Rep. J. Kenneth Robinson (R-Va.) charged that the EPA is "playing fast and loose with the facts" and "frightening the public without justification."

"It's nonsense to suggest that some of these sites . . . may rank among America's most hazardous and pose significant risks to human health and the environment," he said in a prepared statement.

Robinson said the list was issued "apparently to placate political critics who are exploiting the environmental issue in order to get themselves elected to federal office."

Other local officials said there has been no outcry from the community about the IBM plant.

Janet A. Luffy, a spokeswoman for EPA's regional office in Philadelphia, said yesterday that the agency's Superfund list is issued "to determine what are the worst sites in the country, in terms of potential, long-term dangers.

She said that the area around the IBM plant is dependent on groundwater, and that the risk posed by the spilled solvents is serious. "You just don't want the solvents in your groundwater," she added.

"We were very surprised by" IBM's inclusion on the list, said state geologist Samford. "IBM has done everything, and more, than we've asked them."

According to EPA, IBM used the solvents tetrachloroethylene and trichloroethylene to degrease electrical components at the plant. Spills or leaks between 1970 and 1975 have contaminated groundwater at the site with a variety of chlorinated organic solvents, according to analyses by IBM.

Recent IBM tests of private wells near the plant have not produced any sign of the solvents, however, according to Samford.

Manassas Mayor Edgar E. Rohr said he was also surprised. "The company has done all the things they needed to do," he said.