The dirtiest trucks and busses on California roads will have to clean up their act beginning in 2011 -- even those coming in from out-of-state, Canada and Mexico.
Those vehicles are the leading cause of diesel pollution in a state that has some of the smoggiest skies in the country.
The California Air Resources Board made the bold move of mandatory reductions mainly because the related health problems were staggering. The new rules are estimated to prevent from 9,400 premature deaths to 150,000 respiratory ailments over 20 years.
"This is really good news for public health. We've been learning the last few years that diesel emissions, especially those occurring on-road, are one of the biggest health threats we have," said Dr. John Balbus from the Environmental Defense Fund.
Given this recession, trucking companies and other businesses tried to convince the board this is the worst time to force them to make expensive changes.
They would have to either install pollution filters or new engines or just replace their fleet with a newer, cleaner one.
"The cost doesn't change just because the economy is bad. So the only option people have to comply in a bad economy is to basically sell their equipment. They don't have the money to fix it. They don't have the money to replace it," said contractor Mike Lewis.
While truckers showed up in force to testify against the new pollution rule, perhaps it was the testimony of moms that was most convincing.
Anna Sanchez held up a picture of her young asthmatic daughter who she says is sick because of California's bad air.
"My whole family suffers from asthma, I do, my siblings. We just ask you to pass strong diesel truck rules," said Sanchez.
To help with the costs, the state will make several loans and bond monies available to companies to help them comply with the new regulations.