SACRAMENTO, Calif. (AP) -- Fresh off adopting a sweeping plan to reduce greenhouse gases, California air regulators are considering cracking down on pollution from nearly a million diesel trucks that crowd the state's highways each year.
On Friday, the state Air Resources Board was expected to adopt what would be the country's most comprehensive rule to get the dirtiest trucks and buses off the road, including those that travel into California from other states, Canada and Mexico.
The heavy-duty trucks that cart food, electronics, toys and other goods are the leading cause of diesel pollution in a state that has some of the smoggiest skies in the country.
"The health benefits of this rule are just enormous," Air Resources Board chairwoman Mary Nichols said. "We're talking about thousands of lives saved."
The regulation would require owners of some of the oldest and most polluting trucks, school buses, motor coaches and street sweepers to begin transforming their fleets as soon as 2010.
It is a critical element of California's strategy to clean up its smoggy skies and meet state and federal air standards. The new rules would reduce ozone-eating nitrogen oxides and soot-forming particulate matter that can become embedded in lung tissue.
The idea is to speed up the replacement of thousands of trucks and buses that are usually on the road for decades and are not as clean as newer model vehicles that have stricter emission standards mandated by the federal government.
If the rules are adopted, old diesel vehicles would have to be outfitted with pollution filters or new engines or be replaced with newer, cleaner vehicles. The cost to businesses, school districts and transit agencies statewide is estimated at $5.5 billion.
That's a price the trucking industry and others say they can't afford, since the recession has left many truck and bus owners struggling to pay the bills.
"With this economy, this puts us in an untenable position," said Robert Ramorino, president of the California Trucking Association, which wants more time to meet the proposed mandates.
Ramorino said he and many truck owners would be forced to replace relatively new trucks for which they are still paying.
Regulators point out that the costs will be spread over 16 years and say they are dwarfed by the estimated $48 billion to $68 billion in health benefits to Californians who currently breathe diesel fumes.
By the time the regulation is fully implemented in 2023, regulators estimate the amount of diesel particulate matter and nitrogen oxides emitted from these vehicles would be cut by about a third.
The two pollutants can lead to premature death and increased asthma and heart attacks. The proposed rule is projected to prevent 9,400 premature deaths over 20 years, according to an analysis by the board.