Growing up in a polluted world: Population-based studies of air pollution exposure and child brain development

Air pollution is one of the leading environmental risk factors for adverse health outcomes worldwide, with children being particularly vulnerable due to their rapid development and immature defense capacities. This thesis investigated the impact of air pollution exposure on brain development, cognitive functioning, psychiatric symptoms, and allostatic load in children, drawing on longitudinal neuroimaging data and population-based cohorts from the Netherlands and across Europe.<br/>The first part of the thesis identified susceptible periods of pregnancy and early life during which air pollution exposure was particularly harmful to the developing brain. Exposure to multiple pollutants was associated with structural and functional brain differences, including smaller subcortical volumes, poorer white matter organization, and altered functional connectivity. Notably, exposure to PM₂.₅ and copper during pregnancy was associated with smaller hippocampal volumes, but these associations attenuated with increasing age. In contrast, exposure to multiple pollutants during pregnancy and childhood was linked to persistently lower white matter integrity and altered resting-state connectivity patterns across childhood. The second part examined whether higher exposure to air pollution was associated with differences in cognitive functioning and psychiatric symptoms in children, but observed no consistent evidence of harm. The third part found that higher PM₁₀ exposure was associated with elevated allostatic load in children of a multi-country European sample, driven primarily by metabolic and immune/inflammatory markers, although no associations were observed in a Dutch cohort that consisted of slightly younger children.<br/>Taken together, the findings of this thesis contribute to a growing body of evidence linking air pollution to child neurodevelopment and physiological stress. The results underscore the importance of longitudinal study designs and the need to consider multiple exposure windows and outcomes. Together with the existing literature, these findings highlight the necessity for continued efforts to translate the accumulated evidence on the adverse effects of air pollution on child health into meaningful political and policy change.<br/>