Traffic Air Pollution Can Impair Human Brain Function Within Just Two Hours, Study Finds

Researchers at the University of British Columbia and the University of Victoria have found just how quickly air pollution can negatively impact the human brain. While previous studies have found links between traffic pollution and negative health outcomes, this study has found that diesel exhaust exposure can impair the brain in as little as two hours.

The research, published in the journal Environmental Health, is the first of its kind to show changes in the brain’s functional connectivity following traffic-related air pollution. The brain’s functional connectivity measures how different parts of the brain interact with each other, but air pollution can affect these communications when humans are exposed to diesel exhaust.

“For many decades, scientists thought the brain may be protected from the harmful effects of air pollution,” Dr. Chris Carlsten, senior study author and professor and head of respiratory medicine and the Canada Research Chair in occupational and environmental lung disease at the University of British Columbia, said in a statement. “This study, which is the first of its kind in the world, provides fresh evidence supporting a connection between air pollution and cognition.”

The researchers used a controlled lab setting to conduct their experiments, in which they exposed 25 healthy adults, ages 19 to 49, to diesel exhaust and filtered air. Exposures lasted for varying amounts of time. Before and after each exposure, the team used functional magnetic resonance imaging (fMRI) to measure brain activity and how its different parts interacted.

The findings showed that after exposure to diesel exhaust, there was decreased functional connectivity throughout the default mode network of the brain, which includes regions of the brain that are important for thoughts and memories.

“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 Dr. Jodie Gawryluk, a psychology professor at the University of Victoria and first author of the study. “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 team noted that while the exposure did impact brain activity, the impairment was temporary. But they warned that long-term exposure could lead to long-lasting impairments, and they warned that people should try to minimize exposure to traffic pollution, and other forms of similar air pollution, such as fire smoke.

Carlsten recommended that people keep their car filters in good condition and leave the windows rolled up when stuck in traffic to minimize the exposure to exhaust fumes. For those who walk or bike, they may consider taking a less busy route. 

In London, commuters will soon have an app to help them determine routes with the least pollution, technology that may become more widespread as studies like this determine how traffic pollution can impact the human brain.

The study authors also hope that the findings can impact policy regarding traffic pollution to protect public health.