Inhaling diesel exhaust while sitting in traffic for just a few hours can impair brain function and cognition, a new study shows.
Traffic pollution has long been linked to memory problems, but long-term exposure was widely believed to pose the greatest risk.
Researchers in Canada have found that the damage causes measurable changes in just two hours.
Air pollution not only affects neurological health, it also increases the risk of death from all causes.
Diesel exhaust caused neurological connectivity damage that specifically affected a part of the brain called the default mode network that plays a role in people’s internal thoughts and memories
In the new study published in the journal Environmental Health, researchers from the University of British Columbia and the University of Victoria exposed 25 individuals aged 19 to 49 to filtered air and air contaminated with diesel exhaust in a laboratory at various times for 120 minutes.
During that time, subjects in the study rode a stationary bike with light exercise for about 15 minutes to increase inhalation.
All subjects underwent an MRI scan before and after each exposure to monitor brain activity at different stages.
They found that inhaling diesel exhaust reduced functional connectivity, a measure of how parts of the brain interact and communicate with each other, compared to inhaling filtered air.
Dr. Chris Carlsten, a senior study author, said: ‘People might want to think twice the next time they get stuck in traffic with the windows down.’
“It’s important to make sure your car’s air filter is in good condition, and if you’re walking or cycling down a busy street, consider diverting to a less busy route.”
The researchers specifically focused on changes in the brain’s default mode network (DMN), a set of regions in the brain that are more active during passive tasks than tasks that require focused external attention.
Damage to the DMN affects several parts of the brain, including the medial prefrontal cortex, posterior cingulate cortex, inferior parietal lobe, lateral temporal cortex, and the forming hippocampus.
Activity in the DMN peaks when we are awake and not engaged in any specific mental exercise.
We can daydream, reminisce, imagine the future, monitor our surroundings, consider the intentions of others, and so on.
Dr. Jodie Gawryluk, a psychologist at the University of Victoria and the study’s first author said: ‘We know that altered functional connectivity in the DMN has been associated with reduced cognitive performance and symptoms of depression, so it is concerning to see traffic pollution disrupting these networks.’
“While more research is needed to fully understand the functional consequences of these changes, it is possible that they could impair people’s thinking or ability to work.”
The standard mode network has a variety of functions that can be hampered after spending hours stuck in traffic on your commute. The DMN is a center for self-reflection and shows activity while worrying about who we are, our personality traits, and our feelings.
The DMN plays a role in our memory of the past. Its functionality is crucial to our ability to retain episodic memories, or detailed records of events that happened during specific moments in our lives.
The team’s findings offered a glimmer of hope: The neurological effects caused by exposure to exhaust fumes were short-lived. However, long-term exposure to daily traffic commutes will significantly increase health risks.
The study said: ‘Real world exposures tend to be more persistent, especially in regions of the world for which levels such as those we use are not uncommon.
‘It is hypothesized that chronic exposure is, in fact, a series of short-term exposures (to which our participants were exposed to only one) that eventually leads to accumulated stress deficits on allostatic load… but whether this applies to pollution in the neurocognitive domain , although hypothetical, requires further study.’
The fact that exposure to diesel exhaust can damage the brain is not a new finding in itself. In 2008, Dutch researchers followed 10 volunteers who were hooked up to an electroencephalograph (EEG) and exposed to air for 30 minutes in a laboratory polluted with diesel fumes adjusted to levels typical of a busy city street.
At the time, researchers noticed that the people’s brains showed a stress response, indicative of altered information processing in the cerebral cortex, that continued to increase even after the subjects were taken out of the fumes.