The Effects of Air Pollution on Brain Development

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In recent years the topic of climate change has become increasingly popular, with many scientists’ warnings about the irreparable damage it will cause if no action is taken. It is also known that air pollution causes some kind of biological damage as we inhale particles from the air which subsequently enters our bloodstream. Additionally, a new study from The University of Southern California (USC) has found that a particularly fine pollutant particle known as PM2.5 may be affecting neurological development in children.

PM2.5 refers to atmospheric particulate matter (PM) that has a diameter of less than 2.5 micrometers. They are small enough to enter the lower respiratory tract and cause oxidative stress which is the imbalance between free radicals (oxygen with an uneven number of electrons) and antioxidants in the body. This form of stress can also cause systemic inflammation, which puts stress on the body, and toxic effects on the nervous system and brain. Several epidemiological studies have indicated that PM2.5 exposure may especially harmful to children, as their brain continues to develop across childhood and their 30s.

Effects of PM2.5
Source: Eastbourne-air. Air Pollution and Our Health. (2019)

Researchers at USC aimed to examine how annual PM2.5 exposure is related to gray matter morphology, in 10-year-olds enrolled in the Adolescent Brain Cognitive Development Study (ABCD). Gray matter refers to the part of the brain which contains most of the neural cell bodies which include regions involved in muscle control and sensory perception, i.e. seeing, hearing, memory, etc. In order to collect data researchers used MRI scans from about 11,000 children aged 9-10 from 21 different cities across the US and matched each scan with yearly pollution data from each child’s residence. FreeSurfer, a brain imaging software was also used to quantify cortical surface area, cortical thickness, and subcortical and cerebellum volumes in each hemisphere.


Source: TechnologyNetworks. Gray Matter vs White Matter. (2019)

It was found that annual residential PM2.5 exposure was associated with hemispheric and region-specific differences in gray matter. However, no associations were found with cognitive function as measured by the NIH toolbox. Additionally, researchers found a regional-specific association between PM2.5 exposure and cortical thickness of the frontal lobe, temporal lobe, and basal ganglia, as well as differences in associations by hemisphere. These differences in regions and hemispheres have been identified in a number of neurodevelopmental and mental health disorders such as ADHD, depression, and Autism, however, more research is needed in order to fully understand if and how environmental exposures contribute to brain maturation and the development of such disorders.

Interestingly, this study is the first of its kind, demonstrating that at relatively low levels, current PM2.5 exposure may be an important environmental factor that influences patterns of neurological development in children in the US. As the study was only recently conducted, no conclusive long-term effects have been determined in those exposed to PM2.5. This said, USC researchers plan to follow-up with the ABCD study cohort in order to better determine how current levels of PM2.5 exposure may affect neurological development and subsequent risk for cognitive and emotional impairment during teenage years.

Original Source: Cserbik, D., et al. (2020). “Fine particulate matter exposure during childhood relates to hemispheric-specific differences in brain structure.” Environ Int 143: 105933.

Link: https://www.sciencedirect.com/science/article/pii/S0160412020318882

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