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BRain dEvelopment and Air polluTion ultrafine particles in scHool childrEn

Final Report Summary - BREATHE (BRain dEvelopment and Air polluTion ultrafine particles in scHool childrEn)

BREATHE (BRain dEvelopment and Air polluTion ultrafine particles in scHool childrEn) is a population neuroscience study assessing whether exposure of children to traffic related air pollutants (TRAPs) in schools adversely affects neurodevelopment. Exposure to TRAPs during pregnancy or infancy has been related to cognitive impairment and behavioral disorders in children but there is no evidence on the role of TRAPs in schools on cognitive function and neuroimaging. Children spend a large proportion of their day at school and many schools are located in close proximity to busy roads.
Children (n=2897) aged 7 to 10 years from 39 high and low TRAPs schools, paired by socio-economic status, were tested via a series of four computerized tests from January 2012 to March 2013 in Barcelona (Catalonia, Spain) to evaluate working memory development, executive attention, impulsivity, and selective attention. Behavioral problems (Strengths and Difficulties Questionnaire) were reported by parents. Attention Deficit and Hyperactivity Disorder (ADHD_DSM IV) was reported by teachers. MRI (T2, flair, spectroscopy and DTI) and fMRI (resting, visual and audition stimuli) were conducted in around 300 children. To assess gene-environment interaction GWAs was conducted in 80% of the children and DNA-based inflammatory markers (telomere length and mitochondrial DNA) were measured. Air pollution (nitrogen dioxide (NO2), ultrafine particle number (UFP), and particulate matter (PM) < =0.25 µm (quasi-ultrafines), 0.25 to 2.5 µm (accumulation mode), 2.5 to 10 µm (coarse mode), < =2.5 µm (PM2.5) and organics (PAHs)) was measured during two one-week campaigns both inside the classroom and in the courtyard simultaneously in each school pair during 2012. A total of 1,092 PM filters were collected and elements and hydrocarbons were analyzed. Traffic noise in the classroom and traffic intensity at school entrance was directly measured. Residential air pollution exposure was based on modeled geographical estimates. Similar protocol was applied to the 9 year follow-up of the INMA birth cohort children to replicate the results.
The children performed 10,973 cognitive tests. Cognitive functions increased notably (around 10% per year) during primary school years. TRAPs showed high variability across schools related to the traffic intensity and peaks. Some of the TRAPS (carbon particles) showed a high indoor penetration. Indoor PM levels were higher than outdoor due to continuous resuspension of soil particles and a mixed indoor source largely including organic and Ca-rich particles.
Children attending schools with higher TRAPS (largely diesel pollutants such as EC and UFP), had a smaller improvement with age in cognitive development (in all measured cognitive functions). Similarly, TRAPS were associated with more frequent behavioral problems. Only fine particles generated from traffic (no from other origins) showed the association with brain development. TRAPS were associated with lower functional integration and segregation in key brain networks using neuroimaging which indicates slower brain maturation. These chronic relationships were independent of the acute effects, though the short-term exposures to TRAPs (the day before) were also associated with daily fluctuations in attention. Furthermore, noise inside the classroom is related to attention deficit and hyperactivity disorder symptoms, but the effects of TRAPS were independent of noise. In addition, we proved that green space is beneficial for brain maturation (function and structure) and that moderate video-gaming is beneficial for brain functioning but at certain level is related to behavioral problems. Overall, school air is relevant for a healthy brain development. Results imply cost-benefit interventions in schools to endorse the protection of child brain maturation from traffic exhausts.