In a victory for Maryland's coal mining and industrial interests, the General Assembly passed legislation yesterday that would substantially relax state air quality standards so they would match less stringent federal antipollution requirements.

If signed by Acting Gov. Blair Lee III, the measure would greatly benefit coal-burning industries, including utilities, by allowing them to burn less costly, lower grade coal. Coal companies in western Maryland also would substantially increase their sales.

The impact of laxer standards on the state's air quality is not expected to be severe during most times of the year, health experts said. But the bill's opponents warned of even greater air stagnation in urban areas during sticky summer months.

The legislation received final approval in the Senate yesterday, culminating several weeks of lobbying by utilities, manufacturing interests and western Maryland legislators. The measure passed the House of Delegates earlier in the session.

"We need to make it more attractive for businesses to locate in Maryland at low cost," said Sen. Edward J. Mason, the minority leader from Allegany County. "We need an industrial base. We need air quality standards, but they shouldn't be ridiculous."

Sen. Julian L. Lapides (D-Baltimore), noting that Baltimore has one of the highest cancer rates in the nation, argued, "This is a terribly significant bill and a major change in state policy. If we pass this bill, we are negating one of the best laws on our books."

"I've thought all along the federal government should set all (air pollution) standards," said Senate Majority Leader Roy N. Staten, a former employe of Bethlehem Steel Corp., a large coal-using industry. "Air knows no boundaries at all."

The thrust of the complicated legislation is to lower state standards for sulfur dioxide pollution to match the federal ceiling. The state's maximum allowable levels now are 27 percent lower than those tolerated by the federal government.

While sulfur-dioxide pollution is generally not a problem during the cool months of the year, a high concentration of the pollutants in stifling summer weeks often higts levels considered dangerous to public health, especially for persons with respiratory problems.

The legislation is not expected to have much impact on the Washington area because the Potomac Electric Power Co., one of the area's main industries, already is exempted from Maryland's sulfur-dioxide emission standards and burns a lower grade of coal.

As a result of the lower sulfur standard, Pepco saved $32 million in fuel costs in the past year, according to a company spokesman. A spokesman for Baltimore Gas & Electric Co. said the lower standards would save his company $45 million a year.

George P. Ferreri, head of the state's Air Quality Control Bureau, said industries like BG&E would be unable to increase emissions of pollutants soon because the area's air quality is worse than federal standards allow.