The US study of 100,000 births found that pollutants from traffic increase the risk by up to 30%.
Researchers looked at births within five miles of air quality monitoring stations in Los Angeles County, from 2004 to 2006.
The study found that exposure to pollutants, such as polycyclic aromatic hydrocarbons (PAH), linked to car exhausts, led to a 30% increased risk of giving birth prematurely.
The results also show that chemicals produced by diesel fumes were associated with a 10% higher risk of premature birth, while ammonium nitrate fine particles were linked to a 21% increase.
The study, published in the journal
Environmental Health, states: ‘Numerous studies have associated air pollutant exposures with adverse birth outcomes, but there is still relatively little information to attribute effects to specific emission sources or air toxics.’
It continues: ‘These latest analyses provide additional evidence of traffic-related air pollution's impact on preterm birth for women living in Southern California and indicate PAHs as a pollutant of concern that should be a focus of future studies.’
Dr Beate Ritz, from the University of California, one of the study authors, said to reduce the impact of pollutants on health it is ‘important that accurate modelling of local and regional spatial and temporal air pollution be incorporated into pollution policies’.
The researchers compared information from health officials about the babies and their mothers with air pollution statistics to measure their impact.
