Cars and trucks are responsible for more than half the smog-forming emissions in urban areas.

Gallon for gallon, the 2006 lawn mower engines contribute 93 times more smog-forming emissions than those of 2006 cars.

Sharp reductions in smog-forming emissions are also likely, she said.

He said the Prius gets 40 to 50 miles to the gallon and produces 90 percent less smog-forming emissions than the Navigator.

By the Administration's estimate, that would ultimately remove 80 percent of the smog-forming emissions produced by even the cleanest gasoline cars.

Ultimately, using clean fuels in all vehicles would reduce smog-forming emissions by 10 percent - far more than almost any other control strategy.

The retooling costs at refineries will be substantial; so will the reductions in smog-forming emissions and carbon monoxide.

"If automakers don't reduce smog-forming emissions, greenhouse gases and the need for petroleum, I believe we won't be in business."

Ford claimed to have eliminated nearly three million pounds of smog-forming emissions from their U.S. cars and light trucks over the 2004 to 2006 model years.

Those smog-forming emissions can be filtered with a catalytic converter.