Urban air pollution affects structural and functional processes of brain maturation in children

Abstract

Introduction From conception to young adulthood, the human brain undergoes dynamic changes in both its structural and functional organization. This period of life is particularly vulnerable to environmental insults that may interfere with the cascade of neurodevelopmental processes. Exposure to urban air pollution has been associated with poorer cognitive performance, which is thought to be a result of direct interference with brain maturation. We aimed to assess the extent of such potential effects of urban pollution exposure during the prenatal period and the childhood. Methods A group of 263 children, aged 8 to 12 years, underwent magnetic resonance imaging to quantify regional brain volumes and functional connectivity in major neural networks and activation / deactivation dynamics during a sensory task. Prenatal NO2 exposure was estimated using both the mothers address during pregnancy and the data from an urban background monitoring station. A combined measurement of elemental carbon and NO2 in the school environment was used to assess urban air pollution exposure during the childhood period. Results While the children exposed to low prenatal NO2 levels showed an increase in white matter volume (WMV) with advancing age, no WMV progression was observed in the children exposed to higher prenatal levels. Similarly, in the opposite effect to that of age, a higher content of pollutants in the school environment was associated with lower functional integration and segregation in key brain networks relevant to both inner mental processes (the default mode network) and stimulus-driven mental operations. Conclusion Both prenatal and postnatal air pollution exposure appear to adversely affect the structural and functional brain maturation. Further research is needed to determine to what extent these disruptions in the brain maturation process are involved in the poor cognitive performance previously observed in children exposed to air pollution.