Aria Bendix – NBC News
Parts of California, Oregon and Montana are experiencing dangerous levels of air pollution due to several wildfires in the area, including the Park Fire in Northern California, which has become the fifth-largest in that state’s history. Because smoke can travel hundreds or thousands of miles, it poses a health hazard to people even if they are not near the fire.
The tiny particles in that smoke aren’t just bad for your lungs. A number of studies in recent years have found that they also negatively affect your brain, increasing the risk of dementia, cognitive and mental health problems.
“Much of the research on wildfire smoke has focused on our lungs and hearts,” said Stephanie Cleland, an associate professor at Simon Fraser University who studies the health impact of wildfire smoke. “The shift in focus to cognitive impact and mental health is more recent.”
The latest addition to the list of evidence: Research presented Monday at the Alzheimer’s Association International Conference suggests that wildfire smoke could increase the chances of a dementia diagnosis.
The study analyzed medical records of more than 1.2 million adults aged 60 or older in Southern California between 2009 and 2019.
Researchers looked at where people lived to determine their exposure to fine particulate matter from wildfire smoke and other forms of pollution. Their results showed that the odds of developing dementia increased by 21% for each additional microgram per cubic meter of fine particles from smoke that participants were exposed to, on average, for three years.
In contrast, the same increase in exposure to fine particles from other sources, such as cars or factories, was linked to a 3% increase in the odds of developing dementia.
The evidence is preliminary but shows that chronic exposure to wildfire smoke contributes to cognitive decline, said study author Dr. Holly Elser, a neurology resident at the Hospital of the University of Pennsylvania.
However, she said, “the threshold at which wildfire smoke begins to pose a risk for dementia is unknown.”
A study published in August also found that increased exposure to fine particulate matter from a variety of sources, including wildfires, could be associated with higher rates of dementia.
Wildfires are becoming more frequent and intense due to the climate emergency, increasing many people’s exposure to smoke. The frequency of extreme wildfires more than doubled between 2003 and 2023, according to a recent study.
Scientists believe the reason wildfire smoke affects the brain is that the tiny particles it contains can cross the barrier between the bloodstream and the brainwhich causes inflammation in the central nervous system. The particles could also travel directly to the brain through the nose, which in turn can affect people’s ability to think, learn or remember.
The impact of smoke on learning
Dementia isn’t the only potential consequence. A 2022 study found that adults who had recently been exposed to wildfire smoke performed worse on a brain-training game that measures skills like memory, attention, flexibility, processing speed and problem-solving ability.
“Within hours and days of smoke exposure, we saw significant reductions in people’s ability to pay attention,” said Cleland, one of the study’s authors.
Another study, published that same year, showed that exposure to wildfire smoke during the school year lowered students’ test scores compared to a smoke-free year.
“The more smoke you breathe, the worse you do on tests,” said Marshall Burke, an associate professor of Global Environmental Policy at Stanford University who co-authored the study. “The impact on a single student is probably small, but if you add up the results for all students in schools, it amounts to significant losses in overall learning.”
However, Burke said he has some doubts about the findings published this week because wildfire smoke and other forms of pollution “are not an apples-to-apples comparison.”
Elser acknowledged that many questions remain about the effects of smoke on the brain. It is not clear, for example, whether smoke triggers dementia in healthy people or only among those who were already at risk.
“It’s a really intriguing question whether this is creating new cases of dementia that would never have occurred or whether it’s simply accelerating the onset of clinically evident dementia,” she said.
Other questions that linger relate to the link between wildfire smoke and mental health. A February study found that exposure to wildfire smoke in the Western United States was associated with increased emergency room visits for anxiety. Air pollution in general has been shown to be associated with depression and psychotic disorders such as schizophrenia.
Elser said it’s possible that wildfire smoke alters people’s brain chemistry, potentially leading to depression and anxiety. But it’s also possible that the anxiety and stress of experiencing or living through a wildfire could independently lead to mental health problems.
Other problems arising from smoke
Other health consequences of wildfire smoke are much better understood. Scientists have known for decades that when fine smoke particles are inhaled, They can travel deep into the lungs or enter the bloodstream.which increases the risk of asthma, strokes, heart attacks, lung cancer, and weight loss in newborns.
Cleland said it’s not just people living in fire-prone areas who have to worry about these risks, as demonstrated by last summer’s Canadian wildfires, which blanketed parts of the Midwest and Northeast in smoke.
“Last summer completely changed our conversation about who is exposed to wildfire smoke,” she said. “Oregon, California, Washington and British Columbia received a lot of wildfire smoke, but that doesn’t mean places like the Northeast U.S. or Ontario weren’t affected.”
To reduce exposure to wildfire smoke, experts recommend that people in areas with an air quality index of 100 or higher avoid outdoor activities, close all windows, use indoor air filters and wear an N95 mask if they need to leave their homes.
