Traffic pollution can impair human brain function in just a couple of hours, a new study suggests.
It is the first time that an experiment has found evidence of altered brain network connectivity in humans due to air pollution.
"For many decades, scientists thought the brain may be protected from the harmful effects of air pollution," said senior study author Dr Chris Carlsten, head of respiratory medicine at the University of British Columbia (UBC) in Canada.
“This study, which is the first of its kind in the world, provides fresh evidence supporting a connection between air pollution and cognition."
How is traffic pollution impacting us?
Being in the vicinity of idling traffic is certainly unpleasant on the senses, but the study points to more insidious effects.
The researchers briefly exposed 25 healthy adults to diesel exhaust and filtered air at different times in a laboratory setting at Vancouver General Hospital.
Brain activity was measured before and after each exposure using ‘functional Magnetic Resonance Imaging’ (fMRI). This technique measures brain activity by detecting changes associated with blood flow; when a particular part of the brain is being used, blood flow to that area increases.
The researchers watched for 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 common levels of diesel exhaust, compared to filtered air.
"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.
"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."
How can you protect yourself from traffic fumes?
Thankfully, the changes in the brain were temporary and participants' connectivity returned to normal after the exposure.
Though 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're breathing and take appropriate steps to minimise their exposure to potentially harmful air pollutants like car exhaust.
How can we minimise the impact of traffic fumes?
While it may be tempting to drive around with the windows down, especially in warm weather, this lets all the damaging fumes into your car.
"People may want to think twice the next time they're stuck in traffic with the windows rolled down," said Dr Carlsten, who is also the Canada Research Chair in occupational and environmental lung disease at UBC.
Checking your car’s systems is also important.
"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."
While the current study only looked at the cognitive impacts of traffic-derived pollution, the professor added that other products of combustion are likely a concern.
"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," says 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 neurocognitive disorders, it's an important consideration for public health officials and policymakers."