Purpose or Case Report: Traffic-related air pollution (TRAP), a complex mixture of particulate matter, metals,
elemental and organic carbon, polycyclic aromatic hydrocarbons, and other constituents, is strongly associated with
cardiopulmonary health effects. Evidence suggests the developing brain may also be a target organ for these particles
due to translocation either from the respiratory system or through the olfactory nerve. Using an established pediatric
epidemiological cohort with extensive longitudinal exposure assessment since infancy, we tested the hypothesis that
exposure to TRAP during critical windows of brain development is significantly associated with changes in brain
structure and organization. Our imaging study design targeted recruitment of participants from the cohort with the
highest and lowest quartiles of exposure at time of birth.
Methods & Materials: One hundred forty six participants (mean age 12.1 years, 57% male, 73% white, 55% high
TRAP exposure) completed a high-resolution (1 mm3) anatomical imaging protocol with a 32-channel head coil at 3
Tesla. We evaluated brain volume and cortical thickness using the Computational Anatomy Toolbox for SPM 12
software running in Matlab. We derived diffusion metrics (fractional anisotropy (FA), mean (MD), axial (AD) and radial
(RD) diffusivity) by employing a 32-direction, diffusion tensor imaging sequence (b values 0, 800 s/mm2). Analyses
were performed using DTI Studio and custom software. Exposure to TRAP at birth was estimated using a previously
developed land use regression model. One-way ANOVA and multiple linear regression analyses were used to
investigate the relationship between brain volume, cortical thickness, and diffusion metrics with TRAP exposure,
respectively.
Results: Children with high TRAP exposure levels at time of birth were associated with regionally specific reductions in
brain volume and cortical thickness, particularly within the posterior frontal lobe, at 12 years of age compared with
children with low TRAP exposure (Figure 1). Higher exposed participants at birth demonstrated regions with
diminished FA, increased MD, and RD within the right frontal lobe (Figure 2). In addition, higher exposed participants
showed within the posterior left frontal lobe increased FA, AD and decreased RD (Figure 3).
Conclusions: Different regional patterns in brain structure and organization may reflect variability in TRAP effects at
time birth on the development of the brain cortex and white matter, especially with axonal structure and myelination.