Pregnant women may want to steer clear of traffic jams: A new study has found that exposure to traffic pollution can boost the risk of having a premature birth by up to 30 per cent.
The findings are based on 100,000 births over a 22-month period in the car-centric metropolis of Los Angeles. The researchers used data from an extensive network of air-quality monitoring stations, and matched that information with where the women lived.
The study, published in the journal Environmental Health, revealed that the chances of having a "preemie" rose steadily with increasing exposure to traffic-related contaminants.
This isn't the first study to suggest that pollution can be hazardous to a developing fetus. But it is one of the largest research efforts to chart the distribution of exhaust fumes in an urban area.
"There are scientists who don't believe that preterm birth can be affected by air pollution," said the senior author of the study, Beate Ritz of the school of public health at the University of California, Los Angeles.
"We did this study to convince our colleagues that this is a real effect."
Depending on local geography and weather conditions, traffic pollutants tend to disperse from some areas while concentrating in others. Some pollutants are especially worrisome, Dr. Ritz said.
For instance, polycyclic aromatic hydrocarbons (or PAHs) were associated with up to a 30-per-cent increased risk of premature birth among women with the highest levels of exposure. Other toxic substances, such as benzene and fine particulate matter from diesel fumes, were linked to a 10-per-cent rise in the preterm births, while ammonium nitrate fine particles pushed up the odds by 21 per cent.
Premature births are common, accounting for almost one in 10 deliveries. Dr. Ritz said the study results suggest that a significant proportion of preterm births among the most exposed women may be tied to traffic pollution.
Although most preemies are within a few weeks of the full 37-week term, some are very premature. These infants may face life-long health and developmental problems.
Dr. Ritz said she usually advises pregnant women to stay off roadways as much as possible. But, she acknowledged, "you don't really have a choice when you have to go to work." What's needed, she added, are government policies designed to curb emissions.