Women who live close to busy, pollution-spewing freeways are more likely than most to have a premature or low-birth-weight baby, concludes a new Canadian study that adds to the debate over vehicle emissions.
The results do not mean that pregnant women should move out of homes in the shadow of major throughways, says the University of Montreal scientist who spearheaded the research. But they do suggest planners ought to avoid building highways near residential districts -- or houses near existing highways, said Dr. Mélissa Généreux, a community-medicine resident at the university.
"There is a need for action," she said in an interview on Wednesday. "If we could re-organize the environment, we could do a lot to help society."
Curiously, the study showed proximity to a freeway to be a risk factor for affluent and well-educated women, but not poorer ones. That is likely because other factors that affect lower-income mothers disproportionately -- such as smoking and poor nutrition -- make the effect of the highway less statistically obvious for them, the authors say.
Even before the Montreal study, research had found evidence that air-pollution can lead to poor birth outcomes. Either the pollutants directly cause a problem by entering the mother's body and crossing into the womb, or they indirectly harm the fetus by making women more susceptible to respiratory disease, said Dr. Généreux.
There had been little study, though, into the impact of actually living close to a known source of air pollution, like the multi-lane, controlled-access roads that cut through many Canadian cities.
The University of Montreal researchers analysed Quebec government data on almost 100,000 births in Montreal between 1997 and 2001. Postal codes and map software were used to identify those mothers who lived within 200 metres of an expressway -- about 6% of the total. Census data and other information showed income levels within different neighbourhoods and the women's education level.