Those polluting engine-powered mowers that are a staple of suburban lawn care would become much cleaner under emission limits proposed Tuesday...

WASHINGTON — Those polluting engine-powered mowers that are a staple of suburban lawn care would become much cleaner under emission limits proposed Tuesday by the Environmental Protection Agency.

The regulators’ proposal follows a long-running dispute between California Democratic Sen. Dianne Feinstein and Missouri Republican Sen. Kit Bond, who has sought to block the change in order to protect a Missouri small-engine maker, Briggs & Stratton Corp.

Walk-behind and riding mowers and other garden equipment account for up to 10 percent of summertime smog-forming emissions from mobile sources in some parts of the country.

The EPA’s new proposal applies to engines under 25 horsepower, which power nearly all walk-behind and riding lawn mowers as well as small generators and other devices. The rule would cut smog-forming emissions from the engines by 35 percent; the reductions would probably be accomplished by adding catalytic converters that reduce pollution from exhaust.

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The rule would take effect in 2011 for riding mowers and 2012 for push mowers and would apply only to new engines.

Adding catalytic converters will make mowers more expensive, and some in the industry resisted the change. The California Air Resources Board has estimated that walk-behind mowers will cost 18 percent more under the new regulation.

The rule also would put new emission controls on powerboat and outboard engines starting with the 2009 model year that would result in a 70 percent reduction in smog-forming emissions from those engines, EPA said. Public comment is being accepted on the proposed rule until Aug. 3.

Overall, EPA said that the pollution sources being regulated by the new rule account for about 25 percent of all mobile-source hydrocarbon emissions.

“The bottom line is these standards are long overdue but they will be absolutely essential in order to help many parts of the country meet public-health standards,” said Frank O’Donnell, president of Clean Air Watch, an environmental advocacy group.