Early Exposure to Air Pollution and Children's Developing Brains

Representative image,  AP Photo

"The take-home message is that the quality of air we breathe matters, especially to our children."
"This [fewer brain cells and fewer brain connections resulting from poor air quality], in turn, can alter or impair function, depending on where it is located and when this is occurring."
"A question we haven't answered yet is whether these results are the brain failing to develop properly or if brain cells are dying due to exposure. If it's a developmental problem, it's possible the brain can rewire itself to compensate."
"If established cells are dying, the change to function can be more pronounced and possibly permanent."
Travis Beckwith, research fellow, Imaging Research Center, Cincinnati Children's Hospital Medical Center, Ohio

A new study, recently reported in PLoS ONE, suggests that high levels of exposure to traffic-related air pollution may lead to structural changes in the brain of the very young. Reduced thickness of the cortex and decreased grey matter volume were seen in 12-year-old children through brain scans. The children lived under a quarter of a mile distance from a major highway at one year of age. A thinner cortex and less grey matter may correlate with fewer brain cells and fewer connections to the brain.

Dr.Beckwith, lead author of the recently-published study, explains that the cerebellum whose function is to handle fine-tuning in motor control and which may also play a role in regulating emotions and behaviour, was also seen to be affected. In the interests of determining the potential impact of traffic-related air pollution, Dr.Beckwith and his research colleagues took MRI scans of 135 children who had participated in a larger research project.

That long-term study, the Cincinnati Childhood Allergy and Air Pollution Study, recruited families of children under six months of age for the purpose of examining the health impact of early childhood exposure to air pollution. At ages one, two, three, four and seven, child participants in the study were brought to the clinic until the last check-in at age twelve. Caregivers filled out questionnaires enquiring about the children's health, general well-being, housing characteristics and residential history, at each visit.

Air pollution may impact children's mental health

Children were assessed on reading ability, executive function, mental health, intelligence and other neurodevelopmental outcomes at age twelve. Using data from an air sampling network that included 27 sites in the Cincinnati area, estimates for pollution exposure for each child identified outcomes.

The researchers found that children exposed to the highest pollution levels possessed thinner cortexes in comparison with those children with little pollution exposure -- once other factors that might influence brain development, such as maternal IQ and neighbourhood poverty level were taken into account.

"The primary motor cortex is responsible for planning out movements and the execution of those movements."
"The primary sensory cortex [is involved in] tactile senses, such as how things feel, sensing temperature and vibrations as well as identifying objects based on touch."
"The results of this study, though exploratory, suggest that where you live and the air you breathe can affect how your brain develops"
"While the percentage of loss is far less than what might be seen in a degenerative disease state, this loss may be enough to influence the development of various physical and mental processes."

These brain images of 12-year-old children show regions of the brain in red, orange and yellow that are most affected by traffic-related air pollution (TRAP). Those regions denote a reduction in cortical thickness linked to elemental carbon attributed to traffic. Of these images, the darker the color, the stronger the effect. Image is credited to Cincinnati Children’s Hospital Medical Center.