COMMUTING can be hazardous to your health in more ways than one. 

Aside from the dangers from reckless drivers and road obstructions, breathing in diesel exhaust fumes impairs functional brain connectivity in humans, according to a study published in January in BioMed Central.

Researchers from the University of Victoria and University of British Columbia delved into the effects of exposure to traffic-related air pollution, which has been associated with adverse cardiovascular and respiratory effects.

They found that exposure to diesel exhaust led to short-term decreases in default mode network functional connectivity compared to exposure to filtered air. 

The default mode network is a set of regions in the brain that is active during passive tasks, and it is believed to be used when people are remembering or engaged in internal thought.

This reduction in brain function from diesel exhaust, though short-term, may still lead to adverse effects in daily life, the researchers noted. 

“There are several ways in which decrements in brain connectivity, such as those we demonstrated, might manifest in daily life. Changes in brain connectivity have been associated with decreased working memory and behavioural performance, and deterioration in productivity at work (which is also associated with air pollution). It is also possible that these decrements worsen further in the context of multifaceted exposures not studied here,” they said. 

How the study was conducted 

The researchers studied 25 adult participants who were tested immediately pre- and post-exposure to diesel exhaust and immediately pre- and post-exposure to filtered air for comparison.

The exposure lasted for 120 minutes, during which the subjects cycled on a stationary bicycle at light effort for 15 minutes during the first quarter of each hour to maintain a representative level of activity. 

The subjects’ brains were then studied through magnetic resonance imaging or MRI pre and post exposure. 

What researchers found 

The researchers found small but significant differences when they compared the groups exposed to diesel exhaust and filtered air.

They said the participants had greater functional connectivity in widespread regions of the default mode network following exposure to filtered air compared to following exposure to diesel exhaust.

In short, exposure to diesel exhaust led to a decrease in functional connectivity compared to exposure to filtered air.

Researchers said the precise functional impact of the changes seen in the functional MRI are unknown and may be modest given the limited exposure of the subjects. But they noted that real-world exposures could be more persistent.

The study results also support findings suggesting that exposure to air pollutants is associated with decreased functional connectivity, they said. 

What next? 

The researchers said the findings on the effect on brain function could add to the already strong evidence on the adverse effects of air pollution and could put pressure for emissions control. 

“This data may be informative therein, while deepening the evidence base for direct evidence of neurocognitive effects due to acute exposure to [traffic-related air pollution]. As the changes in cognition we have demonstrated may put individuals at risk for impaired vocational performance, this is an important consideration for public health,” they said.