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Introduction: Children are more vulnerable to the effects of environmental elements. A variety of air pollutants are among the identified factors causing neural damage at toxic concentrations. It is not obvious, however, to what extent the tolerated high levels of air pollutants are able to alter brain development. We have specifically investigated the neurotoxic effects of airborne copper exposure in school environments. Methods: Speed and consistency of motor response were assessed in 2836 children aged from 8 to 12 years. Anatomical MRI, diffusion tensor imaging, and functional MRI were used to directly test the brain repercussions in a subgroup of 263 children. Results: Higher copper exposure was associated with poorer motor performance and altered structure of the basal ganglia. Specifically, the architecture of the caudate nucleus region was less complete in terms of both tissue composition and neural track water diffusion. Functional MRI consistently showed a reciprocal connectivity reduction between the caudate nucleus and the frontal cortex. Conclusions: The results establish an association between environmental copper exposure in children and alterations of basal ganglia structure and function. © 2016 The Authors. Brain and Behavior published by Wiley Periodicals, Inc. ; This work was supported by the European Research Council under the ERC (grant number 268479) ?the BREATHE project. The Agency of University and Research Funding Management of the Catalonia Government participated in the context of Research Group SGR2014-1673. We acknowledge C. Persavento, J. Gonz?lez, L. Bouso, M. L?pez, and P. Figueras their contribution to the field work. We also acknowledge all the families and schools participating in the study. ; Peer reviewed

Background Polycyclic aromatic hydrocarbons (PAHs) have been proposed as environmental risk factors for attention deficit hyperactivity disorder (ADHD). The effects of these pollutants on brain structures potentially involved in the pathophysiology of ADHD are unknown. Objective The aim of this study was to investigate the effects of PAHs on basal ganglia volumes and ADHD symptoms in school children. Methods We conducted an imaging study in 242 children aged 8–12 years, recruited through a set of representative schools of the city of Barcelona, Spain. Indoor and outdoor PAHs and benzo[a]pyrene (BPA) levels were assessed in the school environment, one year before the MRI assessment. Whole-brain volumes and basal ganglia volumes (caudate nucleus, globus pallidus, putamen) were derived from structural MRI scans using automated tissue segmentation. ADHD symptoms (ADHD/DSM-IV Scales, American Psychiatric Association 2002) were reported by teachers, and inattentiveness was evaluated with standard error of hit reaction time in the attention network computer-based test. Results Total PAHs and BPA were associated with caudate nucleus volume (CNV) (i.e., an interquartile range increase in BPA outdoor level (67 pg/m3) and indoor level (76 pg/m3) was significantly linked to a decrease in CNV (mm3) (β = − 150.6, 95% CI [− 259.1, − 42.1], p = 0.007, and β = − 122.4, 95% CI [− 232.9, − 11.8], p = 0.030 respectively) independently of intracranial volume, age, sex, maternal education and socioeconomic vulnerability index at home). ADHD symptoms and inattentiveness increased in children with higher exposure to BPA, but these associations were not statistically significant. Conclusions Exposure to PAHs, and in particular to BPA, is associated with subclinical changes on the caudate nucleus, even below the legislated annual target levels established in the European Union. The behavioral consequences of this induced brain change were not identified in this study, but given the caudate nucleus involvement in many crucial cognitive and behavior processes, this volume reduction is concerning for the children's neurodevelopment. © 2017 The Authors ; Marion Mortamais is supported by a Marie Sk?odowska-Curie Individual Fellowship (H2020-MSCA-IF-2014; EU project 656294). This work was supported by the European Research Council under the ERC [grant number 268479]?the BREATHE project. The Agency of University and Research Funding Management of the Catalonia Government participated in the context of Research Group SGR2014-1673. We also thank the Caixa Foundation for their financial support in the PAHs analyses. ; Peer reviewed