Brief exposure to diesel exhaust can affect human brain function

A new study by researchers at the University of British Columbia and the University of Victoria shows that common levels of traffic pollution can impair human brain function in just a matter of hours.

The peer-reviewed results published in the journal environmental healthshows that just two hours of exposure to diesel exhaust causes a decrease in functional brain connectivity — a measure of how the study provides the first evidence in humans, from a controlled experiment, of altered brain network connectivity caused by air pollution.

“For several decades, scientists have believed that the brain may be protected from the harmful effects of air pollution,” said study senior author Dr. Chris Carlstein, professor and chair of the Department of Respiratory Medicine and Canada Chair of Research in Occupational and Environmental Pulmonology at the University of British Columbia. “This study, which is the first of its kind in the world, provides new evidence supporting the relationship between air pollution and cognition.”

For the study, researchers briefly exposed 25 healthy adults to diesel exhaust and filtered air at various times in a laboratory setting. Brain activity was measured before and after each exposure using functional magnetic resonance imaging (fMRI).

The researchers analyzed changes in the brain’s default mode network (DMN), a group of interconnected brain regions that play an important role in memory and internal thinking. Functional magnetic resonance imaging revealed that participants had reduced functional connectivity in diffuse areas of the DMN after exposure to diesel exhaust, compared to filtered air.

We know that altered functional connectivity in the DMN has been associated with decreased cognitive performance and depressive symptoms, so it is troubling to see traffic pollution interrupting these same networks. While more research is needed to fully understand the functional effects of these changes, it is possible that they may impair people’s thinking or their ability to function.”

Dr Judy Gorelock, professor of psychology at the University of Victoria and first author of the study

Take steps to protect yourself

Notably, the changes in the brain were temporary and the participants’ communication returned to normal after the exposure. Dr. Carlsten speculated that the effects could be long-lasting when the exposure is continuous. He said people should pay attention to the air they breathe and take appropriate steps to reduce their exposure to potentially harmful air pollutants such as vehicle exhaust.

“People may want to think twice the next time they’re stuck in traffic with the windows open,” said Dr. Karlstein. “It’s important to make sure your car’s air filter is working well, and if you’re walking or biking on a busy street, consider switching to a less busy road.”

While the current study only looked at the cognitive effects of pollution from traffic, Dr. Carlsten said other products of combustion are likely to be a concern.

“Air pollution is now recognized as the greatest environmental threat to human health, and we are increasingly seeing the effects across all major organ systems,” says Dr. Karlstein. “I expect that we will see similar effects on the brain from exposure to other air pollutants, such as wildfire smoke. With the increasing incidence of neurocognitive disorders, this is an important consideration for public health officials and policymakers.”

The study was conducted at the University of British Columbia’s Air Pollution Exposure Laboratory, located at Vancouver General Hospital, which is equipped with a state-of-the-art exposure booth that can simulate what it’s like to breathe a variety of air pollutants. In this study, which was carefully designed and approved for safety, the researchers used freshly generated exhaust that had been diluted and aged to reflect real-world conditions.


Journal reference:

Gawryluk, JR, et al. (2023) Brief exposure to diesel exhaust impairs brain functional connectivity in humans: a randomized controlled study. environmental health.

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