The Environmental Protection Agency yesterday proposed standards to reduce levels of airborne lead, a pollutant it said is particularly harmful to children.

The rules would have their heaviest impact on lead and copper smelters, which the EPA estimated would have to spend $600 million changing their facilities to reduce lead pollution.

Children have a lower tolerance than adults to lead. Lead in the body can cause damage to nervous and blood-forming systems.

"Our health effects information indicates a need for increasing concern about low-level, long-term exposure to lead, particularly among children," EPA Administrator Douglas Costle said. "Blood lead levels for most children in this country are higher than they should be . . ."

Until now the EPA has attacked lead pollution by requiring a gradual phaseout of the use of lead in gasoline. Because of the use of air pollution control devices on newer model cars which must run on lead-free gasoline, the agency has estimated that air-borne lead pollution will drop about 60 per cent by 1985 from current levels.

The Natural Resources Defense Council won a 1975 court case against EPA, however, saying the agency had to regulate all sources of lead pollution, not just that caused by gasoline. Yesterday's proposed regulations were the result of that decision.

David Schoenbrod, a staff attorney for the council, called the proposal "a victory because five years of litigation have now resulted in the beginning of a national program to protect health from lead pollution.

"This phase of the litigation is now over because EPA has begun to do its legal duty by assessing the voluminous medical data and making a hard judgment as to how much lead in the air our bodies can colerate."

The standard the EPA is proposing is that lead content may not exceed 1.5 micrograms per cubic meter of air, figured on a monthly basis. Four states have laws governing overall lead pollution - California 1.5 micrograms, Pennsylvania 5; Oregon 3, and Montana 5.

The Federal standard would supersede the state levels.

EPA will publish a final standard in June, 1978. After that, the states will have nine months to implement the rule and then from three to five years to make sure plants and other pollution sources comply.