FRIDAY, Oct. 7 (HealthDay News) -- Traffic-related air pollution may put pregnant women at risk for a premature birth, according to a new study.

Researchers looked at 100,000 births among women in California who lived within five miles of an air quality monitoring station. The births spanned a 22-month period from June 2004.

Exposure to traffic-related air pollutants such as polycyclic aromatic hydrocarbons (PAH) was associated with up to a 30 percent greater risk of premature birth; exposure to ammonium nitrate fine particles was associated with a 21 percent increased risk, and exposure to benzene and fine particulate matter from diesel fumes was associated with a 10 percent higher risk, the University of California researchers found.

The study is published online Oct. 6 in the journal Environmental Health.

"Air pollution is known to be associated with low birth weight and premature birth. Our results show that traffic-related PAH are of special concern as pollutants, and that PAH sources besides traffic contributed to premature birth," Dr. Beate Ritz said in a journal news release.

"The increase in premature birth risk due to ammonium nitrate particles suggests secondary pollutants are also negatively impacting the health of unborn babies. To reduce the effects of these pollutants on public health, it is important that accurate modeling of local and regional spatial and temporal air pollution be incorporated into pollution policies," Ritz added.

More information

The U.S. Centers for Disease Control and Prevention has more about premature birth.