Pregnant women who live in polluted areas risk damage to their children's lungs, a new study has warned. Researchers said exposure to pollution during the second trimester of pregnancy in particular raises the risk of harm to a child's lungs.

The finding underlines the multiple public health benefits of policies to reduce exposure to air pollution.

While previous research has highlighted the adverse effects of air pollutants on lung function in school-age children and adolescents, the effects of a mother's exposure to pollution on the lung function of her unborn child and shortly after birth are less well known. Researchers led by Eva Morales of the Centre for Research in Environmental Epidemiology in Spain, set out to examine the association of exposure to air pollution during specific trimesters of pregnancy and postnatal life with lung function in children.

Nitrogen dioxide (NO2) is a widely used marker of traffic-related air pollution, and benzene levels can reflect industrial activities and are considered as a surrogate for a mixture of predominantly traffic-driven pollutants. Analysis of the results showed that exposure to higher levels of benzene and NO2 in pregnancy was associated with reduced lung function parameters in breathing tests. Children whose mothers lived in a high traffic air pollution area for benzene during the second trimester of pregnancy had a 22 per cent higher risk of impaired lung function than those living in less polluted areas. The risk for children of mothers living in a high traffic air pollution area for NO2 during their second trimester was 30 per cent higher than those from less polluted areas.