Air pollution exposure during fetal life increases risk of mental disorders later

Studies in past have linked air pollution levels with complications including cognitive decline and fetal growth development.In new study researchers at Barcelona Institute for Global Health (ISGlobal) and Erasmus University Medical Center of Rotterdam used a population-based cohort to evaluate the relationship between air pollution exposure during fetal life and impairment in inhibitory control later in life. They found that exposure to residential air pollution during fetal life was linked with brain abnormalities that may contribute to impaired cognitive function in school-age children and increased risk of mental health disorders. The study has been published in Biological Psychiatry.

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 behavior--which is related to mental health problems such as addictive behavior and attention-deficit/hyperactivity disorder. Exposure to fine particles during fetal 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 fetal life onward. Researchers assessed air pollution levels at home during the fetal life of 783 children. The data were 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% 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," said Dr. Mònica Guxens, lead author and researcher of ISGlobal and Erasmus University Medical Center.

The fetal 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.