Breathing in diesel exhaust while sitting in traffic for just a couple of hours can impair brain function and cognition, a new study shows.
Traffic pollution has long been linked to memory problems but it was generally thought that long-term exposure posed the biggest risk.
Researchers in Canada have found that the damage causes measurable changes within just two hours.
Air pollution not only erodes neurological health, it also increases a person’s risk of death from all causes.
Diesel exhaust fumes caused neurological connectivity damage specifically affecting a region of the brain called the default mode network, which plays a part in people’s internal thoughts and memories
In the new study published in the journal Environmental Health, researchers at 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 lab at different times for 120 minutes.
During that time, subjects in the study rode on a stationary bike with light effort 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 breathing in diesel exhaust decreased functional connectivity, a measure of how regions of the brain interact and communicate with each other, compared to inhaling filtered air.
Dr Chris Carlsten, a senior study author said: ‘People may want to think twice the next time they’re stuck in traffic with the windows rolled down.’
‘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.’
The researchers specifically zeroed in on changes to the brain’s default mode network (DMN), a set of regions in the brain more active during passive tasks than tasks demanding focused external attention.
Damage to the DMN affects several areas of the brain including the medial prefrontal cortex, the posterior cingulate cortex, the inferior parietal lobe, the lateral temporal cortex, and hippocampal formation.
Activity in the DMN spikes when we are awake and not involved in any specific mental exercise.
We might be daydreaming, recalling memories, envisioning the future, monitoring our environment, thinking about 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’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.’
99% of humans breathe air that exceeds pollution limits
The World Health Organization warned last spring that 99 percent of humans live in an area with unacceptable pollution levels driven primarily by fine particulate matter and nitrogen dioxide.
The default mode network has a variety of functions that could be hampered after hours of sitting in traffic on your commute home. The DMN is a hub for self-reflection and shows activity during rumination about who we are, our personality traits, and our feelings.
The DMN plays a role in our recollection of the past. Its functionality is crucial to our ability to retain episodic memories, or detailed accounts of events that have happened during specific moments in our lives.
The team’s findings offered some glimmer of hope: the neurological effects brought on by exposure to exhaust were short-lived. Though, long-term exposure from daily commutes in traffic will greatly compound the health risks.
The study said: ‘Real-world exposures are often more persistent, particularly in regions of the world for which levels such as those we use are not uncommon.
‘It is hypothesized that chronic exposure is effectively a series of short-term exposures (only one of which our participants were exposed to) that ultimately leads to accumulated deficits through a stress on allostatic load… but whether or not this applies to pollution in the neurocognitive realm, while hypothesized, requires further study.’
The fact that exposure to diesel exhaust can damage the brain is not in and of itself a new finding. In 2008, Dutch researchers monitored 10 volunteers who were hooked up to an electroencephalograph (EEG) and exposed for 30 minutes to air in a lab polluted with diesel fumes adjusted to levels typical of a busy city street.
In that time, researchers saw that the peoples’ brains displayed a stress response, indicative of changed information processing in the brain cortex, which continued to increase even after the subjects had been removed from the fumes.