Exposure to air pollution during pregnancy is associated with poorer cognitive development in infants as early as six months old, according to new research from Spain.
The study is the first to use eye-tracking technology to objectively measure how prenatal pollution affects early brain function.
Carmen Peuters, ISGlobal researcher and first author of the study, explained: ‘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.’
Researchers from the Barcelona Institute for Global Health (ISGlobal) followed 168 mother-child pairs, assessing infants at six and 18 months of age. They measured exposure during pregnancy to several pollutants, including PM 2.5, nitrogen dioxide (NO₂) and black carbon (BC), using detailed models that accounted for time spent at home, at work and commuting.
To test cognitive performance, babies completed an eye-tracking Visual Paired-Comparison task. They were shown a familiar face and a new face side-by-side; typically, infants look longer at the novel image, a sign of healthy recognition memory. The team measured this ‘novelty preference.’
The results revealed that higher prenatal exposure to air pollution was linked to a lower novelty preference. For example, an increase in black carbon exposure was associated with a 2.5% decrease in novelty preference. The strongest negative associations were found for black carbon, PM₂.₅, and the copper content of PM₂.₅.
Peuters said: ‘Our findings suggest that the prenatal period is a window of particular vulnerability for the developing brain. The results were consistent even after accounting for factors like maternal education, smoking, and infant age.’
The study also found preliminary evidence that boys might be more susceptible to the negative cognitive effects of air pollution than girls, aligning with some previous research, though this requires further investigation.
This research adds to growing evidence linking air pollution to neurodevelopmental risks – some of which has also been undertaken by ISGlobal – but stands out by using an objective, physiological measure in infancy rather than relying on parent reports or later childhood tests. The eye-tracking method offers a non-invasive way to detect subtle, early changes in memory and attention.
Jordi Sunyer, BiSC project coordinator and senior author of the study: ‘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 foetus, which may interfere with brain development.’
The full research can be read here.
Photo: Mohsen Ebrahimpour / Unspash
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