A recent study by scientists from the University of British Columbia and the University of Victoria. The peer-reviewed findings, published in the journal Environmental Health, show that just two hours of exposure to diesel exhaust causes a decrease in functional connectivity of the brain.
The study provides the first evidence from a controlled experiment of altered brain network connectivity induced by air pollution in humans. “For many decades, scientists thought that the brain could be protected from the harmful effects of air pollution,” said Dr. Chris Carlsten, professor and chief of respiratory medicine and the Canada Research Chair in Occupational and Environmental Lung Disease at UBC.
“This study, which is the first of its kind in the world, provides new evidence supporting a link between air pollution and cognition.”
For the study, researchers exposed 25 healthy adults to diesel exhaust and filtered air at different times in a laboratory setting. Brain activity was measured before and after each exposure using functional magnetic resonance imaging (fMRI).
The researchers analyzed changes in the brain’s default mode network (DMN), a cluster of interconnected brain regions that play a key role in memory and internal thinking. fMRI revealed that participants had reduced functional connectivity in wider regions of the DMN after exposure to diesel exhaust compared to filtered air.
“We know that altered functional connectivity in the DMN is associated with reduced cognitive performance and symptoms of depression, so it is concerning to see traffic pollution disrupting these same networks,” Dr Jody Gavriluk, Professor of Psychology at the University of Victoria said and the first author of the study.
While more research is needed to fully understand the functional effects of these changes, it is possible that they may impair people’s ability to think or function. Notably, the brain changes were temporary and participants’ connectivity returned to normal after exposure.
Dr Carlsten speculates that the effects may be longer lasting where exposure is continuous. He added that people should be mindful of the air they are breathing and take appropriate steps to reduce their exposure to potentially harmful air pollutants such as car exhaust. “People might want to think twice the next time they are stuck in traffic with their windows down,” Dr Carlston said.
“It’s important to make sure your car’s air filter is in good working order, and if you’re walking or biking on a busy road, consider switching to a less busy route,” Dr Carlston continues.
While the current study only looked at the cognitive effects of traffic-derived pollution, Dr Carlsten said other products of combustion are probably a concern. “Air pollution is now recognized as one of the greatest environmental threats to human health and we are increasingly seeing effects on all major organ systems,” says Dr Carlsten.
“I expect we will see similar effects on the brain from exposure to other air pollutants such as wildfire smoke. With the increasing incidence of neurological disorders, this is an important consideration for public health officials and policy makers.”
The study was conducted at UBC’s Air Pollution Exposure Laboratory, located at Vancouver General Hospital, which is equipped with a state-of-the-art exposure booth that can simulate what it’s like to breathe in a variety of air pollutants.
In this study, which was carefully designed and approved for safety, the researchers used freshly generated extract that was diluted and aged to reflect real-world conditions.