Traffic pollution exposure is known to be harmful to our lungs — but could it also be changing the way our brains work?

A new study by researchers at UBC and the University of Victoria has shown common levels of traffic pollution can impair human brain function in only a matter of hours.

“For many decades, scientists thought the brain may be protected from the harmful effects of air pollution,” says Dr. Chris Carlsten, Professor and head 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 fresh evidence supporting a connection between air pollution and cognition.” 

Ryon Anas participates in an experiment in the Air Pollution Exposure Laboratory (credit: UBC Faculty of Medicine).

The study was conducted at UBC’s Air Pollution Exposure Laboratory, located in Vancouver General Hospital, which is equipped with a stateof-the-art exposure booth that can mimic what it is like to breathe a variety of air pollutants. In this study — carefully designed and approved for safety — researchers used newly generated exhaust fumes that were diluted and aged to reflect real-world conditions.

The focus of their research was on 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 study measured brain activity in 25 healthy adults over periodic exposures to diesel exhaust and filtered air. Brain activity was measured before and after each exposure using functional magnetic resonance imaging (fMRI). The fMRI revealed that participants had decreased functional connectivity in widespread regions of the brain’s DMN after exposure to diesel exhaust, compared to filtered air. 

Despite changes in brain activity being temporary in the study, Dr. Carlsten speculates that the effects could be long-lasting when exposure is continuous.

Altered functional connectivity in the DMN has been associated with reduced cognitive performance, and symptoms of depression. While the current study only investigated the cognitive impacts of traffic-derived pollution, future research will explore how other sources of air pollution, such as forest fire smoke, affect brain health.