WASHINGTON - The nation's farms no longer have to report to authorities the toxic, smelly fumes released from manure.

The Bush administration late Friday completed a regulation exempting farms from reporting releases of hazardous air pollution to federal, state and local authorities. The rule applies specifically to the gases from manure that are often responsible for odor problems.

The Environmental Protection Agency said that the changes will allow responders to focus on spills and releases that require their attention. But environmentalists say the rule will make it difficult to track air pollution problems at farms.

Large farms with hundreds of dairy cows or thousands of pigs will still have to report to local and state authorities.