This week a new cleaner diesel fuel will go widely on sale in the US. The fuel could be a big boost for air quality and may encourage the use of more diesel-powered cars in the US.
A rule introduced this year requiring a 97 percent reduction in the sulfur content of highway diesel fuel phases in Sunday to an estimated 80 percent of the fuel sold in the United States.
The next step comes in January when new diesel truck engines will be required to have special filters to curb emissions even further.
The overall result is "the single greatest achievement in clean fuel since lead was removed from gasoline more than 25 years ago," says US Environmental Protection Agency chief Stephen Johnson.
The agency estimates that by 2030, when most old engines will have been replaced, 20,000 premature deaths, tens of thousands of illnesses, and more than 7,000 hospital visits will be prevented every year.