A traffic jam on a highway.

Those Traffic Jams Are Worse Than You Think

Air pollution from cars is, unsurprisingly, bad for our lungs. But now researchers have evidence of what it might be doing to our brains.


Before the pandemic, the average Canadian spent at least 60 minutes per day commuting to work — and more than half of these commuters did so by car. Even now, after a slight dip in commute times during the pandemic, many Canadian employees have started driving to and from work once more.

It’s no surprise that long commutes by car are bad news for the environment, but according to new research, all this driving may also impact your brain. In a study published in Environmental Health, researchers from the Universities of Victoria and British Columbia investigated how traffic-related air pollution rapidly affects the way your brain functions.

Pollution in the air pollutes your body and mind

Air pollution is one of the leading causes of death worldwide, and according to the World Health Organization, 99% of the global population is at risk. Recent studies have found that long-term exposure to air pollution is just as damaging to our lungs as smoking, and that air pollution can lead to cognitive deficits in children and increased levels of dementia in adults.

Cars are a major source of air pollution around the world, and the team behind this study wanted to learn how diesel exhaust in particular affects our brains. Many of us spend hours each week exposed to car-related pollution during our commutes, and it’s important to know how this pollution is affecting our health.

To learn more, the researchers exposed 25 healthy adults to both diesel exhaust and filtered air at UBC’s Air Pollution Exposure Laboratory in the Vancouver General Hospital. This is a laboratory setting which can safely mimic the effects of different types of air pollution.

The researchers also monitored the study participants’ brain activity before and after being exposed to these air samples. In particular, they were looking for changes in the brain’s default mode network, or DMN, which relates to memory and internal thought.

The team found that after being exposed to diesel exhaust, the study participants showed less functionality in their DMNs compared to when they were exposed to filtered air. Given how often we’re exposed to diesel exhaust and other air pollution throughout our days, these results are particularly worrying. Many commuters likely don’t realize that the time they’re spending in traffic could be having serious impacts on their health.

“For many decades, scientists thought the brain may be protected from the harmful effects of air pollution,” said Chris Carlsten, professor and head of respiratory medicine at UBC and senior author of the study, in a press release. Carlsten is also the Canada Research Chair in occupational and environmental lung disease.

“This study, which is the first of its kind in the world, provides fresh evidence supporting a connection between air pollution and cognition.”

How can we protect our brains?

The good news is that while participants initially showed decrease functionality in their DMNs, their brains returned to normal shortly after the study. More work will be needed to show whether or not the effects are long-lasting, especially after continuous, long-term exposure to air pollution.

In the meantime, the authors recommend that commuters be mindful of the air they’re breathing, and adjust their commutes where possible. For example, commuters who are stuck in traffic jams could consider keeping their windows rolled up to avoid exposure. Commuters who can take alternate routes down less busy streets might consider doing so in order to avoid crowded traffic jams.

The authors also hope that policymakers will take these concerns into consideration. Air pollution is a major health risk around the globe, and will likely only get worse without some sort of intervention.

“Air pollution is now recognized as the largest environmental threat to human health and we are increasingly seeing the impacts across all major organ systems,” Carlsten said.

“With the increasing incidence of neurocognitive disorders, it’s an important consideration for public health officials and policymakers.”

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Emily Deibert is a PhD student in the Department of Astronomy & Astrophysics at the University of Toronto with a passion for science outreach and communication. She earned her HBSc (Astronomy, English, and Mathematics) at the University of Toronto. She is excited about turning scientific research into stories and sharing these stories with the public.