Hope that lawnmowers, leafblowers and other small engines will soon spew less smog has run into an unexpected roadblock — safety.

A Senate (search) committee approved a compromise Thursday that requires federal regulators to first study the safety of more environmentally friendly small engines before requiring manufacturers to build them.

The language, added to a big environmental spending bill, is a compromise between a Missouri Republican who wanted to put the new federal rules on hold for even longer and California lawmakers who are trying to reduce their state's smog problems. Environmental groups called it a setback for cleaner air standards.

After some last-minute negotiating, the Senate Appropriations Committee watered down a provision by Sen. Kit Bond (search), R-Mo., that requires the U.S. Environmental Protection Agency to conduct a safety study before issuing new pollution controls for small engines. Bond says the clean-air regulations would make small engines less safe and hurt manufacturing jobs in his state.

The committee action, on a voice vote, sends the bill to the full Senate.

Bond said catalytic converters that would be added to outdoor power tools to make them cleaner may be a fire hazard.

"I always believed the critics would come to see that this study was vital to protect the safety of consumers and prevent accidental fires," Bond said in a statement. "It just doesn't make sense to have a 1,100 degree catalytic converter three inches from your hand, as you use it in dry grass."

Under the new language, the EPA (search) now has only six months after the spending bill is passed to complete its safety study. Bond's original amendment set no time limit.

Bond's critics say the EPA is already six months behind schedule in proposing new rules and claim the study is just a guise to further delay the process.

"No government study has ever been completed on time and there's going to be no consequences if it's not completed on time," said Frank O'Donnell, director of the environmental advocacy group Clean Air Watch. "We are just concerned this will be another excuse for delaying the cleanup of dirty small engines."

The controversy goes back to 2003, when Bond succeeded in passing a measure to prevent all states — except California — from imposing small-engine emissions rules that are more stringent than those under the federal Clean Air Act. At the time, Bond said a national standard was needed.