Air pollution linked to pre-term, smaller babies

Babies are much more likely to be born prematurely or underweight if exposed to high levels of air pollution in the womb, according to a new study released today.

The study of pregnant women in Southwestern Ontario showed even a one-part-per-billion increase in sulfur dioxide levels makes the women 3.4 times more likely to have a low-birthweight baby and twice as likely to give birth prematurely.

The main source of sulfur dioxide emissions is burning fossil fuels, such as coal, oil and natural gas.

“Our findings are in keeping with other research – and evidence is accumulating that toxic air travels through pregnant women’s lungs and are found in their placentas,” said Geography professor Jason Gilliland, a scientist at Children’s Health Research Institute. “There is definitely a major concern for pregnant women who live in areas with high exposure to sulfur dioxide.


Gilliland is also the Director for Western’s Human Environments Analysis Laboratory and the Urban Development Program.

The study, Geospatial analyses of adverse birth outcomes in Southwestern Ontario: examining the impact of environmental factors, published in Environmental Research, sampled more than 25,000 live births at London Health Sciences Centre (LHSC) between 2009-14.

Low birth-weight is defined as a baby born weighing less than 2,500 grams and pre-term birth as born less than 37 weeks of gestation.

In examining the potential causes for low-weight and pre-term births, researchers took into consideration other possible factors such as maternal income and education levels and medical, psychosocial and behavioral reasons.

And even though previous pre-term birth was the single biggest predictor of low birthweight, the only significant environmental variable in the mix was sulfur dioxide levels.

About 67 per cent of sulfur dioxide emissions come from smelters and utilities, with the remainder coming from other industrial sources and vehicle emissions.

Southwestern Ontario – located in the country’s manufacturing heartland and downwind from some of the most industrialized areas of the United States – is an effective proxy for studying the effects of pollution on a population.


“We were able to take advantage of a large neonatal and perinatal database from LHSC,” noted Brescia University College professor Jamie Seabrook, lead author of the study. “Through geographical mapping of maternal postal codes by our HEALab at Western, we tested the relative influence of the various factors.”

The next step will be to identify geographical clusters – or ‘hotspots’ – of sulfur dioxide exposure and adverse birth outcomes.

This will help provide knowledge on where health-promotion efforts need to focus in the future.

Short of a political and industrial commitment to curbing air pollution, recommendations could include suggesting pregnant women limiting their time outside on bad-air days

“While many factors contribute to a healthy pregnancy, the takeaway message is the quality of air women breathe is also important,” said Seabrook. “If health care providers could be informed of the hazards of air pollution to developing fetuses, they could make recommendations to pregnant patients about limiting exposure when air quality is poor.”