Inhaling Hazardous Wildfire Smoke Reaches the Brain, Causing Neurological Perils

While it is common that wildfire smoke harms people already suffering from respiratory problems, among other health effects, another hazard in the smoke was discovered by a university professor.

The report published in the journal Toxicological Sciences tackled the microscopic particles from woodsmoke inhaled into the lungs, but managed to work its way into the bloodstream, even reaching the brain. The neurological risks from this menace can range from premature aging and various forms of dementia to depression, and worse, psychosis.

"These are fires that are coming through small towns and they're burning up cars and houses," said Matthew Campen, Ph.D., a professor in The University of New Mexico College of Pharmacy who led the research.

These microplastics and metallic particles can travel from thousands of miles. A "hidden danger of woodsmoke that might not be dense enough to trigger respiratory symptoms," he adds.

Neurological consequences from inhalation exposure

"It's only these really small ultra-fine particles that travel a thousand miles to where we are. They're more dangerous because the small particles get deeper into your lung and your lung has a harder time removing them as a result."

In the study conducted last year at Laguna Pueblo, these particles have traveled 41 miles west of Albuquerque and nearly 600 miles from the source of wildland fires. The research team found three weeks later that the mice exposed to the smoke-laden air exhibited age-related changes in their brain tissue.

These tiny particles burrow into lung tissue and triggers the release of inflammatory immune molecules into the bloodstream. These are carried into the brain and start to degrade the blood-brain barrier. "That causes the brain's own immune protection to kick in," Campen said.

"It looks like there's a breakdown of the blood-brain barrier that's mild, but it still triggers a response from the protective cells in the brain -- astrocytes and microglia -- to sheathe it off and protect the rest of the brain from the factors in the blood," he explains.

"Normally the microglia are supposed to be doing other things, like helping with learning and memory."

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Burden of aging-related impairments

Interestingly, alongside the neuroinflammatory and neurometabolomic consequences examined from inhalation exposure to naturally occurring wildfires in California, Arizona, and Washington in 2020, researchers found metabolic changes in mice's neurons, suggesting that wildfire smoke exposure may add to the burden of aging-related impairments.

As these particular cells transition to resolution of inflammation subsequent to the 20-day exposure, neurometabolites were decreased, and a hallmark of neurodegeneration, a progressive loss of structure or function of neurons, was observed.

"Neuroinflammation, together with decreased levels of key neurometabolites, reflect a cluster of outcomes with important implications in priming inflammaging and aging-related neurodegenerative phenotypes," the authors wrote.

Even mounting evidence from a previous study shows that the small particles released from fires across the western U.S. and Canada can enter the body and cause adverse mental health outcomes. This points out the fact that these fires do not just pose physical health risks, but damage to our brains as well.

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