Significant controls on vehicle emissions, including the first tightening of auto tailpipe standards since 1981, are necessary if most U.S. cities are to rid themselves of dangerous smog, the American Lung Association reported yesterday.

The report, prepared by Michael P. Walsh, former chief of the Environmental Protection Agency's vehicle control program, is expected to fuel proposals in Congress -- strongly opposed by the auto industry -- for cutbacks in tailpipe discharges of hydrocarbons and nitrogen oxide that form smog in sunlight.

Walsh predicted that even with new restrictions on factory emissions and more vehicles entering service with previously required pollution controls, few cities will achieve federal air quality standards for ozone, the measure for smog.

But nearly all cities could conquer smog by early next century, Walsh said, if Congress approves vehicle controls in pending bills, including more stringent and durable antipollution devices. The measures would provide 38 percent of the additional reductions needed to achieve the clear air standards, the report estimated.

Congress had set a deadline of last Dec. 31 for cities to clean up smog, which can cause respiratory and pulmonary problems. With more than 50 metropolitan areas failing to meet the deadline, Congress granted an eight-month grace period while it debated the issue.

In November, meanwhile, the EPA filled the breach with a plan directing state governments to choose their own methods -- curbs on polluting industries or car pooling, for example -- to achieve standards in their cities. The agency was criticized for failing to further tighten tailpipe emissions.

Richard D. Wilson, the EPA's director of air pollution from mobile sources, said yesterday that stricter tailpipe controls would only reduce hydrocarbons by one percent and that most cities can achieve the ozone standards if they cut back industrial sources of pollution and adopt pending agency regulations restricting gasoline volatility, capturing gasoline fumes and improving vehicle maintenance.

Tim McCarthy, a lobbyist for the Motor Vehicle Manufacturers Association, said Walsh's report was "based on illusions" by stating that tighter tailpipe controls can improve air quality. He said the auto industry does not have the technology to further cut hydrocarbons.

In support of the report, David Hawkins, spokesman for the National Clean Air Coalition, said that Walsh's estimate that stricter auto emission controls can achieve 38 percent of necessary pollution reductions counters "a lot of hand-waving that it's no longer effective or productive to go after automobile pollution."