EPA’s Garden Variety Idea: Regulate Lawn Equipment : Environment: Mowers, saws and other gas engines account for 10% of nation’s pollution. New rules signal need for tighter controls to further clear the air.

The Environmental Protection Agency announced Wednesday that it will reach into the nation’s garden sheds to regulate the source of about 10% of air pollution: lawn mowers, chain saws, leaf blowers and other garden equipment.

EPA Administrator Carol Browner, standing on the manicured lawn of the Washington Monument in a driving spring rain, said that the federal government intends to impose unprecedented national emission standards on all new gas-powered garden tools sold in the United States.

“Reducing the emissions from these engines,” she told reporters, “will help us assure that all Americans have clean, healthy air to breathe.”

Americans own 89 million lawn mowers, garden tractors, chain saws and other gas-powered garden and outdoor equipment, according to the EPA.

The homeowner who indulges in the noisy Saturday morning ritual of mowing his lawn for an hour would contribute as much pollution as he would if he drove his modern automobile for 11 1/2 hours, the EPA said.

Officials said that the decision to regulate such small engines is a measure of how far regulators now must reach in their efforts to further cut air pollution. In addition to Wednesday’s announcement, EPA is working on new standards for outboard motors. The boat engines can emit as much pollution in an hour as 800 miles of driving in a typical automobile. Those regulations are to be announced later this summer.

“It’s getting harder and harder to control air pollution,” said Dick Wilson, director of the Office of Mobile Sources in EPA’s air quality bureau. “Despite having spent years and years cleaning up factories and cars, we need to keep looking at sources that 10 years ago didn’t seem that important.”

The government’s decision will become final after a lengthy period for public comment. It will allow the California Air Resources Board, after several years of delay, to enforce similar emission standards throughout California.

The board adopted similar rules in 1990 for “utility engines,” including gas-powered lawn tools, but chose to delay enforcement until the federal government had come up with the same regulations. The purpose was to allow manufacturers of lawn equipment to adhere to a single standard for the entire U.S. market.

Those rules now will go into effect for California consumers in 1995, said Bill Sessa, a spokesman for the state board. The rest of the nation will be subject to the EPA rules in 1996, with manufacturers required to improve the air and fuel mixture used by gas-powered garden equipment to ensure better combustion.

The EPA said that the changes would cost buyers $5 more per new lawn mower. By the year 2003, when the new engines are expected to power most lawn equipment, the changes would reduce carbon monoxide emissions in the atmosphere by 14%, the agency said.

Emissions of hydrocarbons, which contribute both to smog and to the accumulation of “greenhouse gases,” would fall by 32% under the plan, the EPA estimated.

In the second phase of the regulatory plan, the agency expects to reconsider the existing standards and the availability of new technologies, and possibly to propose new standards by 1996. The agency said that potential technologies for powering lawn equipment could include catalytic converters, multiple circuit carburetors, fuel injection systems and four-stroke overhead valves, as well as alternative fuels.

Manufacturers of lawn equipment responded calmly to the rules. They have been partners in negotiating them and have committed tens of millions of dollars to developing cleaner engines.

“We really as a company are positioned to support and respond to the final rules, whatever they are,” said Don St. Dennis, spokesman for The Toro Co. in Bloomington, Minn.