Air pollution exposure in pregnancy ups asthma risk in babies

Babies born to mothers exposed to air pollution from traffic sources during pregnancy have an increased risk of developing asthma before the age of five years, a new study has warned.

Children whose mothers lived close to highways during pregnancy had a 25% increased relative risk of developing asthma before the age of five, researchers said.

Researchers from the University of British Columbia in Canada studied over 65,000 children from birth until the age of 10 years.

They monitored physician-diagnosed asthma cases among this group and also assessed the mothers' exposure to air pollutants during pregnancy.

Each mother's postcode was used and exposure level was determined using three measures - land use regression models, which combine traffic-related air pollutant monitoring data and geographical information around the home address, measurements of air pollutants from monitoring stations close to each mother and assessing whether each mother lived close to a major road.

The measurements focused mainly on traffic-related pollutants, including black carbon, fine particulate matter, nitrogen oxide and nitric oxide.

The findings showed that exposure to air pollution from traffic sources during pregnancy increased the risk of developing asthma during the first 5 years of life, even in urban areas with relatively low levels of pollution.

The risk increased with an increase in levels of nitrogen dioxide and carbon monoxide - two markers of traffic-related air pollution, researchers said.

In addition, children born with a low birth weight were more susceptible to the respiratory effects of air pollution, they said.

The results were found after other factors, such as low birth weight at term, gestational period, breastfeeding and socio-economic factors had been controlled for.

"Our study results highlight the importance of exposure to pollution while babies are still in the womb," said Hind Sbihi from University of British Columbia.

"Air pollution from traffic sources increased the risk of developing asthma during early years before children reach school age, even in an urban area with relatively low levels of air pollution," she added.

The findings were published in the European Respiratory Journal.