Bethlehem Steel Corp., Maryland's largest employer and the Chesapeake Bay's largest source of toxic industrial wastes, has been told by the state to dramatically reduce the pollution in its massive waste-water discharges into the bay by 1987.

The new pollution limits, characterized by environmentalists and federal officials as 10 times tougher than current limits, come at a time when cleaning up the Chesapeake Bay has become a national priority.

Three states -- Maryland, Virginia and Pennsylvania -- as well as the federal government and the District of Columbia, have called for coordinated, long-term efforts to decrease the daily flow of toxic chemicals and sewage into the nation's largest bay.

But Bethlehem Steel's long record of violating clean water standards has prompted environmentalists to wonder whether the giant steel plant in Baltimore will adhere to stricter pollution standards when it has consistently failed to meet the previous ones, and whether the state will be able to enforce the new standards.

"They have a dramatic and consistent history of not complying with their permit," said James Thorton, a lawyer with the Natural Resources Defense Council Inc., which joined the Chesapeake Bay Foundation in bringing suit against the company seeking to force compliance with the old permit.

"They needed the club of federal court order to take their obligation under the law seriously," he added.

In 1977 the company paid a $500,000 fine for repeated violations of its discharge permit.

Last May, U.S. District Court Judge Joseph Young ruled that Bethlehem Steel had regularly violated its discharge permit, and cited 369 permit violations between 1979 and 1984. Young scheduled a trial next March to assess damages against the company.

The two environmental groups that brought the civil suit -- the Chesapeake Bay Foundation and the Natural Resources Defense Council -- are asking for $3 million in remedies.

Company officials, while refusing to discuss the violations, said the stricter standards in the new permit will cost the company about $20 million.

The company will have to install new pollution control equipment at its Sparrows Point mill to scrub lead, chromium, zinc and other heavy metals, as well as oil and grease from the estimated 400 million gallons of water it discharges daily into the Patapsco River, which flows into the bay.

The new permit "will take what already is a sound and conscientious water cleanup program instituted by the company . . . to a higher, more stringent level. We will be removing well over 95 percent of the pollutants in the discharge water," said G. Ted Baldwin, spokesman for the plant. He added that the company has already spent $93 million to control pollution at the plant.

Dismissing the ruling as Young's "opinion," Bill Riley, the company's manager for environmental compliance, said, "Bethlehem should be applauded for accepting that original permit in the first place."

But environmentalists and the Environmental Protection Agency's top official on pollution reduction in the steel industry, said the company has saved millions of dollars over the years by consistently violating its original permit instead of installing pollution control equipment.

That permit, issued under the 1972 Clean Water Act's National Pollution Elimination System (NPDES), expired in 1977. Maryland officials allowed the company to continue operating under that permit while waiting for EPA to publish pollution standards for the steel industry, which the federal agency did in 1982.

"The state was willing to sit back and give them as much time as they wanted -- they just didn't feel pressed to get this new permit out," said Terry Oda, EPA's steel industry specialist. "What was issued last Thursday was a result of a negotiated settlement. The state bent, yeah. I wouldn't say they gave the store away -- they gave part of the store away."

Maryland officials refused to comment on the new permit yesterday, saying they would wait until today, when William Eichbaum, assistant state secretary for environmental programs, formally unveils it.

"This is the kind of permit the government should have issued to Bethlehem Steel five years ago," said Thorton, the NRDC lawyer. "The reason there are permits is so that the water stays clean, or in the case of the Chesapeake Bay, gets cleaned up. The reason for penalties, for fines, is so that companies understand that it's cheaper to obey the law than to violate it. That's really what you're trying to teach them."