Prenatal exposure to pollution impacts infant cognitive development

The prenatal period is a critical window for brain development, yet few studies have examined the impact of air pollution exposure during pregnancy on child cognition.

A new study led by the Barcelona Institute for Global Health (ISGlobal), a center supported by the "la Caixa" Foundation, in collaboration with the University of Barcelona (UB), shows that prenatal exposure to pollution is associated with lower cognitive performance in newborns. These findings highlight the importance of reducing air pollution exposure, especially during pregnancy, to protect neurodevelopment.

The study, published in Environmental Pollution, included data from 168 mother-child pairs participating in the BiSC (Barcelona Life Study Cohort) project, conducted in Barcelona between 2018 and 2023. Researchers assessed total exposure to nitrogen dioxide (NO₂), black carbon (BC), particulate matter (PM_2.5), and the copper (Cu) and iron (Fe) content in PM_2.5 during pregnancy using advanced models that combined pollution estimates with time-activity information at home, workplaces, and during commuting.

A novel method for assessing cognitive development

Cognitive development was assessed using eye-tracking, a non-invasive technique that evaluates how infants process visual information. A total of 180 infants participated at 6 months of age, with 75 re-evaluated at 18 months. During the test, infants were first familiarized with an image and then presented with two images simultaneously: one familiar and one new. The system recorded gaze duration for each image. A longer gaze at the new image, known as "novelty preference", indicates recognition of the familiar image and better memory performance.

This is the first study to examine the relationship between prenatal exposure to air pollution and child neurodevelopment using an eye-tracking task. This approach provides a more objective, direct measure that does not rely on clinician-administered scoring or caregiver reports, making it a robust and innovative tool for assessing early cognitive development."

Carmen Peuters, Study First Author and Researcher, Barcelona Institute for Global Health (ISGlobal)

Exposure to pollution reduces cognitive performance

The analysis found that higher prenatal exposure to air pollutants leads to lower novelty preference in visual memory tasks, indicating lower cognitive performance in newborns. The strongest associations were observed for black carbon, PM_2.5, and copper content in PM_2.5. For all pollutants, associations were stronger in boys than in girls, suggesting potential sex-specific vulnerability.

"Several biological mechanisms may explain how prenatal exposure to air pollution affects neurodevelopment. Pollutants can cross the placental barrier, triggering systemic inflammation and oxidative stress in the fetus, which may interfere with brain development," notes Jordi Sunyer, BiSC project coordinator and senior author of the study.

Public health implications

These findings add to growing evidence that air pollution not only harms lung and cardiovascular health but also affects neurodevelopment. In this sense, a previous study by the same team showed that prenatal pollution exposure is associated with changes in fetal brain structures.

"Our results confirm that the prenatal period represents a critical window of vulnerability to environmental exposures and reinforce the need for stricter environmental policies and targeted measures to protect the health of pregnant women and children," emphasizes Joan Birulés, researcher at the University of Barcelona and one of the study's authors.