Exposure to air pollution during pregnancy linked to brain alterations

A new study conducted by the Barcelona Institute for Global Health (ISGlobal) - a centre supported by the "la Caixa" Foundation - and the Erasmus University Medical Center of Rotterdam has linked exposure to residential air pollution during fetal life with brain abnormalities that may contribute to impaired cognitive function in school-age children. The study, published in Biological Psychiatry, reports that the air pollution levels related to brain alterations were within those considered to be safe.

The study showed for the first time a relationship between air pollution exposure and a difficulty with inhibitory control - the ability to regulate self-control over temptations and impulsive behaviour - which is related to mental health problems such as addictive behaviour and attention-deficit / hyperactivity disorder. Exposure to fine particles during foetal life was associated with a thinner cortex - the outer layer of the brain - in several areas of both hemispheres, which is one of the factors that may explain the observed impairment in inhibitory control.

The study used a population-based cohort in the Netherlands, which enrolled pregnant women and followed the children from foetal life onward. Researchers assessed air pollution levels at home during the fetal life of 783 children. The data was collected by air pollution monitoring campaigns, and included levels of nitrogen dioxide and course and fine particles. Brain morphology was assessed using brain imaging performed when the children were between 6 and 10 years old.

The relationship between fine particle exposure, brain structure alterations, and inhibitory control was found despite the fact that the average residential levels of fine particles in the study were well below the current EU limit -- only 0.5 per cent of the pregnant women in the study were exposed to levels considered unsafe. The average residential levels of nitrogen dioxide were right at the safe limit.

This finding adds to previous studies that have linked acceptable air pollution levels with other complications including cognitive decline and fetal growth development. "Therefore, we cannot warrant the safety of the current levels of air pollution in our cities," says Dr. Mònica Guxens, lead author and researcher of ISGlobal and Erasmus University Medical Center. .

The foetal brain is particularly vulnerable --it hasn't yet developed the mechanisms to protect against or remove environmental toxins. "Although specific individual clinical implications of these findings cannot be quantified, based on other studies, the observed cognitive delays at early ages could have significant long-term consequences such as increased risk of mental health disorders and low academic achievement, in particular due to the ubiquity of the exposure," said Dr. Guxens.