Traffic pollution impairs brain network connectivity

A new study led by the University of British Columbia has revealed that traffic pollution impairs brain function in a short matter of time. According to the research, just two hours of exposure to diesel exhaust causes a decrease in the brain’s functional connectivity.

“For many decades, scientists thought the brain may be protected from the harmful effects of air pollution,” said study senior author Dr. Chris Carlsten. “This study, which is the first of its kind in the world, provides fresh evidence supporting a connection between air pollution and cognition.”

For the investigation, 25 adults were briefly exposed to either diesel exhaust or filtered air. The researchers used functional magnetic resonance imaging (fMRI) to measure brain activity before and after each exposure. 

The default mode network (DMN) is a set of interconnected regions in the brain that are activated during internal mental-state processes such as memory retrieval. When the experts analyzed the brain scans, they discovered that there was decreased functional connectivity in the DMN after exposure to diesel exhaust.

“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,” said study first author Dr. Jodie Gawryluk. “While 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.”

The researchers found that brain connectivity changes were only temporary. Dr. Carlsten speculated that the effects could be long lasting where exposure is continuous. He said that people should be mindful of the air they are breathing and take appropriate steps to minimize their exposure to potentially harmful air pollutants like car exhaust.

“People may want to think twice the next time they’re stuck in traffic with the windows rolled down,” said Dr. Carlsten. “It’s important to ensure that your car’s air filter is in good working order, and if you’re walking or biking down a busy street, consider diverting to a less busy route.”

“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. I expect we would see similar impacts on the brain from exposure to other air pollutants, like forest fire smoke. With the increasing incidence of neurocognitive disorders, it’s an important consideration for public health officials and policymakers.”

The study is published in the journal Environmental Health. 

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By Chrissy Sexton, Earth.com Editor

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