Researchers at the University of California, Berkeley, say diesel-powered vehicles are a bigger source of secondary organic aerosol, a major component of smog.
Diesel exhaust is responsible for 65 percent to 90 percent of a region's vehicular-derived SOA, depending upon the relative amounts of gasoline and diesel used in the area, a UC Berkeley release said Monday.
"We can now say that, while both motor vehicle sources are important for these 'secondary' particles, diesel is responsible for a larger portion, especially in regions such as the San Joaquin Valley with a lot of diesel use," study principal investigator Allen Goldstein said.
SOA leads to poor air quality and can cause respiratory problems, the researchers said.
"The data from our study contains the most comprehensive chemical detail to date on diesel and gasoline emissions," study lead author Drew Gentner, a Berkeley doctoral graduate in civil and environmental engineering, said.
"We expect that these findings will help policymakers improve air pollution control measures in the state, and also other parts of the world."
The study was published in the Proceedings of the National Academy of Sciences.