Are gasoline-fueled cars or large diesel trucks the bigger source of secondary organic aerosol (SOA), a major component of smog? UC Berkeley researchers have stepped into this debate with a new study that says diesel exhaust contributes 15 times more than gas emissions per liter of fuel burned.

The study, published today in the Proceedings of the National Academy of Sciences, elucidates the contributions to air pollution from the two types of fuel emissions. The authors estimate that diesel exhaust is responsible for 65-90 percent of a region’s vehicular-derived SOA, depending upon the relative amounts of gasoline and diesel used in the area.

For example, the researchers noted that in the San Francisco Bay Area, about 10 times more gas is used compared with diesel.

SOA contributes to respiratory problems and poor air quality, so pinpointing the major sources of the pollutant is important in evaluating current and future policies to reduce smog in the state.

The new findings contradict previous research that put the blame on gasoline-fueled vehicles as the predominant source of precursors that form secondary organic aerosol.

via Air pollution study clears the air on diesel versus gas emissions.