Even brief exposure to air pollution has rapid and measurable impacts on the human brain, a new study has shown.
Within a matter of hours, diesel exhaust fumes seriously impairs human brain function.
The researchers at the University of British Columbia (UBC) and the University of Victoria used MRI scanners to measure the impact on brain activity.
Senior study author Dr Chris Carlsten, professor and head of respiratory medicine at UBC, said, "For many decades, scientists thought the brain may be protected from the harmful effects of air pollution.
"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 briefly exposed 25 healthy adults to diesel exhaust and filtered air at different times 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 interconnected 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.
Dr Jodie Gawryluk, a psychology professor at the University of Victoria, 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.
"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 changes in the brain were temporary and participants' connectivity returned to normal after the exposure.
Dr Carlsten speculated that the effects could be long lasting where exposure is continuous.
The researchers advise that people take appropriate steps to minimise 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 recognised as the largest environmental threat to human health and we are increasingly seeing the impacts across all major organ systems," said Dr Carlsten.
"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 neuro-cognitive disorders, it's an important consideration for public health officials and policymakers."
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