Wildfires were once a rare occurrence, but as the climate becomes warmer and drier, they’ve become more common and more widespread.
Now, a study has shown they could be putting tens of millions of people at risk of dementia.
It found people exposed to wildfire pollution have an 18 percent higher risk of developing any type of dementia after just three years’ exposure.
While people exposed to pollution not caused by wildfires – such as that from manufacturing or cars – have just a one percent higher risk of dementia.
Long-term exposure to pollutants known as total fine particulate matter (PM2.5) is a recognized risk factor for dementia, but less is known about how the tiny specs of pollution produced by wildfires – ash, carbon monoxide and dioxide, formaldehyde, volatile compounds and various other carcinogens – affect people’s brain.
Researchers studied the medical records of 1.2million people who had been exposed to wildfire pollution for an average of three years from 2008 to 2019 in California.
According to CAL FIRE, there were 90,157 wildfires during that time period, and the study found approximately 81,000 people received a dementia diagnosis during the study period.
The researchers said their results show that wildfires are even more harmful than the already-deadly pollution released by traditional means such as cars and factories.
Flames consume a home as the Mountain Fire burns in Camarillo, California in November 2024
Inmate firefighters battle the Mountain Fire at Swanhill Farms in Moorpark, California in November 2024
PM2.5 is small enough to enter the lungs through inhalation and the researchers believe the particulates then enter the bloodstream and circulate throughout the body, penetrating the brain’s protective barriers.
This, they concluded, can accelerate the deterioration of the brain and lead to dementia.
PM2.5 is also produced by the burning of gas, diesel, wood, manufacturing and refineries, as well as burning candles, though the substances released from wildfires are more damaging, according to the researchers.
The study looked at diagnoses of Alzheimer’s disease, Lewy Body dementia, vascular dementia, frontotemporal dementia, Parkinson’s dementia and unspecified dementia.
An estimated 7million Americans 65 and older had dementia in 2020, and the proportion of adults 70 and older with dementia was 10 percent in 2019.
If current trends continue, more than 9million Americans could have dementia by 2030 and 12million by 2040, according to the Population Reference Bureau.
But researchers from the University of Pennsylvania and Kaiser Permanente in California, who performed the latest study, claimed as wildfires become more common, so too may dementia – and they called for more research into the matter.
They also said more needs to be done about mitigating air pollution on especially vulnerable populations, such as minorities and people who live in more impoverished neighborhoods.
The researchers concluded: ‘As the climate changes, interventions focused on reducing wildfire PM2.5 exposure may reduce dementia diagnoses and related inequities.
‘These latter findings underscore the importance of research that considers the effects of air pollution on potentially vulnerable population subgroups and aims to identify potential strategies to mitigate inequities in air pollution exposure effects.’
The above map shows wildfire hotspots across the US
An estimated 7million Americans 65 and older had dementia in 2020
Data from researchers at the University of Maryland, calculated that the area burned by forest fires increased by about 5.4 percent per year from 2001 to 2023.
PM2.5 refers to the concentration of microscopic airborne particles that are 2.5 micrometers or smaller. They are measured in micrograms per cubic meter (µg/m³).
These pollutants are small enough to penetrate deep into the lungs when breathed in and circulate throughout the entire body, including the brain.
The particulates can produce highly reactive molecules and free radicals.
Excessive productions of these molecules can overwhelm brain cells’ defense systems, leading to cell damage, DNA mutations and impaired cell function.
Excess production has also been implicated in heart diseases, cancer and Alzheimer’s disease.
Researchers also posit wildfire PM2.5 can cause the overactivation of certain types of immune cells that help maintain a healthy balance in the brain, fight infections and help remove harmful debris from the brain.
Their overactivation can lead to harmful effects on the brain and spinal cord.
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Wildfire pollution can also produce an overwhelming amount of something called cytotoxic factors – things that damage or kill healthy living cells.
The researchers added that exposure to PM2.5 may indirectly lead to dementia by disrupting the body’s normal processes, which can increase the risk of blood clots, excessive bleeding, dysfunctions of blood vessels in the brain and stroke, which could be an underlying risk factor for dementia.
About two-thirds of the study participants were diagnosed with unspecified dementia. The second-most diagnosed dementia was Parkinson’s dementia with 13 percent and Alzheimer’s followed with 12 percent.
Other analyses of the data found study participants younger than 75, those from minority groups and people living in high-poverty areas had ‘heightened responses’ to wildfire PM2.5.
According to the study, published in JAMA Neurology, the 2018 wildfire season resulted in an estimated $149billion in healthcare costs, along with capital and economic damages.
