Air pollution exposure during pregnancy and childhood and brain morphology in preadolescents

Studies investigating the relationship between exposure to air pollution and brain development using magnetic resonance images are emerging. However, most studies have focused only on prenatal exposures, and have included a limited selection of pollutants. Here, we aim to expand the current knowledge by studying pregnancy and childhood exposure to a wide selection of pollutants, and brain morphology in preadolescents.

We used data from 3133 preadolescents from a birth cohort from Rotterdam, the Netherlands (enrollment: 2002-2006). Concentrations of nitrogen oxides, coarse, fine, and ultrafine particles, and composition of fine particles were estimated for participant's home addresses in pregnancy and childhood, using land use regression models. Structural brain images were obtained at age 9-12 years. We assessed the relationships of air pollution exposure, with brain volumes, and surface-based morphometric data, adjusting for socioeconomic and life-style characteristics, using single as well as multi-pollutant approach.

No associations were observed between air pollution exposures and global volumes of total brain, and cortical and subcortical grey matter. However, we found associations between higher pregnancy and childhood air pollution exposures with smaller corpus callosum, smaller hippocampus, larger amygdala, smaller nucleus accumbens, and larger cerebellum (e.g. -69.2mm³ hippocampal volume [95%CI -129.1 to -9.3] per 1ng/m³ increase in pregnancy exposure to polycyclic aromatic hydrocarbons). Higher pregnancy exposure to air pollution was associated with smaller cortical thickness while higher childhood exposure was associated with predominantly larger cortical surface area.

Higher pregnancy or childhood exposure to several air pollutants was associated with altered volume of several brain structures, as well as with cortical thickness and surface area. Associations showed some similarity to delayed maturation and effects of early-life stress.