After a prolonged behind-the-scenes struggle and a loud public debate, the Environmental Protection Agency yesterday released a proposal to toughen the standards for lead in gasoline.

At a news briefing, assistant EPA administrator Kathleen Bennett said the proposal would "reduce airborne lead by 31 percent more over the next eight years than we would have reduced had we kept the current rules in effect."

With the new rule, EPA hopes to salvage what has been a public relations disaster for the agency and to end the long-running lead soap opera, which the agency says it never wanted to get involved with in the first place.

The proposal was scheduled to be issued about three weeks ago, but was held up by an 11th-hour dispute with the Office of Management and Budget. A compromise agreed to at a White House meeting last week requires the Reagan administration to issue a final rule by Nov. 1, the day before the 1982 elections.

Eric Goldstein of the Natural Resources Defense Council said the EPA package "sounds pretty good, if adopted in its proposed form. EPA is back on the right track."

Christopher DeMuth, OMB's administrator for information and regulatory affairs, told reporters yesterday that "We think this is a terrific program." He said it would improve health protection while eliminating "economic distortions" in the lead program.

But the new proposal did not please everyone. "This thing started out as regulatory reform in the context of giving relief to business," said Urvan Sternfels, president of the National Petroleum Refiners Association. "This proposal makes the rules more onerous for the most part."

Lead is added to gasoline to raise its octane level, and can enter the air from auto emissions. The substance is known to cause learning disabilities in children, and children who live in cities where traffic congestion is high are the most frequent victims. A study released by the National Center for Health Statistics last year showed that as many as 18.6 percent of black children in some inner-city areas have dangerous levels of lead in the blood.

The existing lead standards, developed during the 1970s, were targeted by the Presidential Task Force on Regulatory Relief a year ago, and last fall OMB directed EPA to weaken the standards. EPA, anticipating strong public protests, resisted until February. Then it offered several options, ranging from maintaining the current standards to abolishing the whole regulatory framework.

Environmentalists, members of Congress and a parade of medical experts immediately blasted EPA's action in reopening the standard.

By June, EPA, already on the firing line for its handling of numerous other environmental health issues, was convinced that weakening the standards was political suicide. "Lead is bad for people, especially children. There's no way around that," said one EPA source. Another added, "We didn't want to give environmentalists the opportunity to go around saying we were in favor of causing retardation in children."

EPA informed OMB of its intention and in July began writing a new proposal. The main part of the package was a proposal prohibiting large refiners from adding more than 1.1 grams of lead per gallon of leaded gasoline. The existing system allows refineries to add 0.50 grams of lead for each gallon of gasoline produced, whether leaded or unleaded. The effect, as production of unleaded gasoline increased, was to permit the addition of greater amounts of lead to leaded gasoline.

The proposal also would continue a small refiners' exemption, established by Congress in the 1977 Clean Air Act amendments and scheduled to expire Oct. 1, and would set the level for small refiners at 2.5 grams per gallon. But it would substantially narrow the definition of small refiners, and would require that the firm had been in existence on or before Oct. 1, 1976.

These changes are intended to reduce the facilities that qualify for the small refiners' exemption from 159 to 74. Most of the facilities that will lose their exemption are blenders, firms that import inexpensive gasoline and add lead to it.

Imported gasoline would also be subject to the 1.10 limit. Currently gasoline refined abroad is not subject to any lead content restrictions.

When EPA completed the proposal at the end of July, it sent a copy to OMB and simultaneously leaked copies to the press and environmentalists. Most observers believe EPA leaked the information to strengthen its hand in overcoming anticipated opposition from OMB.

After reviewing the proposal, DeMuth wrote that during the comment period he would like EPA to consider the "appropriateness" of the 1.1 grams-per-gallon standard for leaded gasoline. In earlier conversations with EPA, DeMuth had suggested that the figure might be too low. OMB also objected to a proposed interim rule requiring that some of the small refiners meet the more stringent eligibility requirements for the special exemption by Oct. 1. OMB wanted the deadline suspended until the final rule was published.

But environmentalists and congressional critics opposed that, fearing that it might take EPA months to approve a final plan. They also objected to delaying any decision until after the November elections.