SUNDAY, March 11 (HealthDay News) -- Gasoline engines produce far more of a particular type of air pollution than diesel engines, according to a new study.

The researchers analyzed air pollution in Los Angeles and were surprised to find that gasoline engines were responsible for most secondary organic aerosols (SOAs), which are tiny particles that can harm human lung and heart health, reduce visibility and affect the climate.

The study confirmed that diesel trucks were used less on weekends than on weekdays, while the use of gasoline-powered vehicles remained nearly constant throughout the week. This led the researchers to expect that weekend levels of SOAs would be lower than weekday levels.

Instead, the researchers found that weekend and weekday levels of SOAs were about the same. This means that gasoline engines are the main source of SOAs, according to the study, slated for publication in the journal Geophysical Research Letters.

"The contribution of diesel to SOA is almost negligible," study leader Roya Bahreini, a research scientist at the Cooperative Institute for Research in Environmental Sciences, said in a journal news release. "Even being conservative, we could deduce from our results that the maximum upper limit of contribution to SOA would be 20 percent."

That means that gasoline engines account for 80 percent or more of SOAs.

"While diesel engines emit other pollutants such as soot and nitrogen oxides, for organic aerosol pollution they are not the primary culprit," said Bahreini, who also works at the U.S. National Oceanic and Atmospheric Administration's Earth System Research Laboratory.

The results suggest that finding ways to reduce SOA levels in emissions from gasoline engines could benefit human health and the environment.

More information

The American Lung Association has more about air pollution and health.