Researchers have, for the first time, demonstrated the effect of exposure to traffic pollution on the brain’s functioning.

In a controlled experiment, healthy volunteers were briefly exposed to diesel exhaust. The scientists watched, in real time, disruptions to the ability of different areas of the brain to interact and communicate with each other.

The experiment suggests that “common levels of traffic pollution can impair human brain function in only a matter of hours”.

The researchers, from Canada’s University of British Columbia (UBC) and University of Victoria, said their study, the first of its kind in the world, “provides fresh evidence supporting a connection between air pollution and cognition”.

The experiment

According to a statement from UBC, the researchers recruited 25 healthy adults who were briefly exposed to diesel exhaust and filtered air, on separate occasions, in a laboratory setting.

Brain activity was measured before and after each exposure using functional magnetic resonance imaging (fMRI).

The researchers analysed changes in the brain’s default mode network (DMN), ‘a set of inter-connected brain regions that play an important role in memory and internal thought’.

The fMRI revealed that participants had decreased functional connectivity in widespread regions of the DMN after exposure to diesel exhaust, compared to filtered air.

Notably, the changes in the brain were temporary and participants’ connectivity returned to normal after the exposure.

The researchers speculated that the effects “could be long lasting where exposure is continuous”.

What the researchers say

Dr Jodie Gawryluk, a psychology professor at the University of Victoria and the study’s first author said:

“We know that altered functional connectivity in the DMN has been associated with reduced cognitive performance and symptoms of depression, so it’s concerning to see traffic pollution interrupting these same networks.

Associate professor Jodie Gawryluk.

She said more research is needed “to fully understand the functional impacts of these changes”.

It’s possible that they “may impair people’s thinking or ability to work”.

Senior study author Dr Chris Carlsten is professor and head of respiratory medicine at UBC. He said:

“For many decades, scientists thought the brain may be protected from the harmful effects of air pollution.

“This study … provides fresh evidence supporting a connection between air pollution and cognition.”

He said that people should be mindful of the air they’re breathing and take appropriate steps to minimize their exposure to potentially harmful air pollutants like car exhaust.