A new study conducted by researchers at the University of British Columbia, Canada, and the University of Victoria, Australia, has shown that typical levels of traffic pollution can damage human brain function in a matter of hours. The results, published in the scientific journal ‘Environmental Health‘, show that just two hours of exposure to diesel engine exhaust causes a decrease in functional brain connectivity, a measure of the brain’s ability to function.
The controlled experiment provides the first evidence in humans of air pollution-induced disruption of brain network connectivity. “For many decades, scientists thought that the brain could be protected from the harmful effects of air pollution,” said Chris Carlsten, lead author of the research. “This study, the first of its kind in the world, provides new evidence supporting a connection between air pollution and cognition,”
The researchers briefly 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).
This study provides new evidence supporting a connection between air pollution and cognition.Chris Carlsten, lead author of the study
“Air pollution is currently considered the greatest environmental threat to human health, and we are seeing increasing effects on all major organ systems,” said Carlsten. “I expect that exposure to other air pollutants, such as smoke from forest fires, will have similar effects on the brain. With the increasing incidence of neurocognitive disorders, this is an important consideration for public health officials and policy makers.”
The researchers analyzed changes in the brain’s default mode network (DMN), a set of interconnected brain regions that play an important role in memory and internal thinking. The fMRI revealed that participants had decreased functional connectivity in large regions of the DMN following exposure to diesel exhaust compared to filtered air.
“We know that impaired functional connectivity in the DMN has been associated with lower cognitive performance and depressive symptoms, so it is concerning to see traffic pollution disrupting these same networks. While more research is needed to fully understand the functional implications of these changes, it is possible that they impair people’s thinking or ability to work,” detailed Jodie Gawryluk, professor of psychology at the University of Victoria and first author of the study.
The changes in the brain were temporary and the participants’ connectivity returned to normal after exposure. Carlsten noted that the effects could be long-lasting when exposure is continuous. He urged people to be aware of the air they breathe and take appropriate steps to minimize their exposure to potentially harmful air pollutants, such as car exhaust.
“People should think twice the next time they find themselves in a traffic jam with their windows down. It is important to make sure the car’s air filter is in good working order, and if walking or cycling on a busy street, consider detouring to a less busy route,” Carlsten said.
Although the study only looked at the cognitive impacts of traffic-derived pollution, the authors noted other combustion products could also be of concern.