Pollution exposure during pregnancy has been linked to lung damage in babies, especially during the second trimester, according to new research.

It has long been documented that exposure to air pollutants can cause adverse medical conditions such as poor lung function, particularly in young children and adolescents. What is less well known is the effects of pollution exposure to pregnant women and its effects on unborn children.

In a long-term study led by Dr. Eva Morales of the Centre for Research in Environmental Epidemiology (CREAL) in Barcelona, scientists analyzed 1,295 pregnant women who attended pre-natal clinics. Two traffic pollutants were measured – benzene and nitrous dioxide – in neighborhoods where the women lived at different times throughout their pregnancy. This data was then used to create a model of exposure for the women, as well as for their babies during their first year of life.

Differences in geography, time of year, climate, and population were accounted for. The lung capacity of 620 children was measured four and a half years later with a spirometer.

The researchers discovered that the children of women who were exposed to higher levels of benzene during months four to six during pregnancy had a 22 percent higher likelihood of having impaired lung function, compared to those who live in less polluted neighborhoods. The risk was 30 percent higher for nitrous oxide.

The association between pollution and impaired lung function was found to be stronger among children with allergies, or from a lower social and economic class.

The authors of the study stress that more needs to be done in order to reduce air pollution to improve public health, particularly when it comes to the lung health of the next generation.