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Smoke from California wildfires could be increasing the risk of dementia, study finds

While the risk of wildfires causing devastation to communities and the environment is well known, new research is showing that the smoke from massive vegetation fires may also have serious effects on the brain.

A study from the University of Michigan published last month, found that wildfires, as well as emissions from farming, may pose especially toxic threats to a person’s cognitive health, even increasing their risk of developing dementia.

The study from Michigan’s School of Public Health found a “strong likelihood” that agriculture and wildfires may be doing more damage than previously thought and will need to be closely monitored and studied for their risks to public health.

“We saw in our research that all airborne particles increased the risk of dementia but those generated by agricultural settings and wildfires seemed to be especially toxic for the brain,” said Sara Adar, associate chair of the Department of Epidemiology in the School of Public Health. Adar is leading multiple studies on the impacts of exposures on cognitive aging and dementia.

A man on a rooftop looks at approaching flames from the Springs Fire on May 3, 2013 near Camarillo, California. (Getty Images)
A man on a rooftop looks at approaching flames from the Springs Fire on May 3, 2013 near Camarillo, California. (Getty Images)

Boya Zhang, a research fellow who studies the effects of air pollution on the body, said this recent study suggests that “particulate matter air pollution from agriculture and wildfires might be more neurotoxic compared with other sources.” Zhang stressed that more research would be need to confirm that hypothesis.

The research focused on 30,000 Americans who were involved in a previous study that looked into the development of dementia over an 18-year period. Data was provided by the Health and Retirement Study, with participants regularly interviewed to provide feedback about their overall health and cognition. Michigan researchers then took that data, focusing on where the participants lived, cross-referenced it with exposure to particulate matter air pollution, and found that those who were exposed more regularly had greater risk of dementia. The findings could not be explained by other factors, researchers added.

“These findings are quite timely given the increasing frequency of wildfire smoke in our
communities,” Adar said. “Our data suggest that in addition to some of the more obvious health impacts of wildfire smoke like irritation to our throats and eyes along with breathing difficulties, high smoke days might also be taking a toll on our brains.”

Unusually poor air quality across the country has regularly triggered public health alerts warning of microscopic toxins in air pollution. Some fine particulate matter is so small it can enter the brain through the nose directly or cross the brain’s protective blood-brain barrier. Some particulate matter is also known to affect the lungs and heart, in addition to the brain.

This year saw a record-number of air quality alerts in the U.S., propelled by massive wildfires in Canada. In California alone, there have have been more than 5,000 wildfires this year with more than a quarter-million acres burned in what is widely considered a “mild” fire season.

Adar said wildfire smoke is becoming a “more widespread stressor” with many cities experiences as many as 30 days or more, in which they are impacted by smoke. Wildfires are believed to contribute up to 25% of the fine particulate matter exposures across the entire country and as much as 50% in western states.

A boat motors by as the Bidwell Bar Bridge is surrounded by fire in Lake Oroville during the Bear fire in Oroville, California on September 9, 2020. (Getty Images)
A boat motors by as the Bidwell Bar Bridge is surrounded by fire in Lake Oroville during the Bear fire in Oroville, California on September 9, 2020. (Getty Images)

Any new health effects linked to wildfires are extra concerning to researchers as global climate change increases the risk of the ecological disaster happening with more regularity.

“While individual wildfires may be short-lived, these events are becoming more frequent in our communities due to warmer temperatures, drier conditions, and longer fire seasons. As we’ve seen, wildfire smoke can also travel very far distances,” Adar said.

The purpose of the study was mainly to provide evidence to policymakers about the risks of exposure to these emission sources.

Dementia, which is the seventh-leading cause of death in the world and one of the major causes of disability for older people, could take years to develop, so any evidence of a possible increased risk factor is critical in understanding and possibly preventing it.

“With the knowledge of which sources are more toxic than others, it may be possible to design interventions for specific sources as a more effective way to decrease the burden of dementia,” Zhang said.

A similar study published by the University of New Mexico found that wildfire smoke could cause inflammation of the brain that can persist for months or longer. That inflammation can be found in the hippocampus, the region of the brain responsible for learning and memory.

In addition to increased risk of dementia, wildfire could also be affecting your memory and overall mood, researchers theorized.

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