The destruction caused by the recent Palisades, Eaton, and Hughes Fires in Los Angeles County is hard to put into words. Together, they have burned nearly 50,000 acres, destroyed more than 16,000 structures, and killed at least 29 people, according to reports from NBC News. Even though these fires are mostly now contained, those affected have a long, difficult journey ahead.
In addition to rebuilding, dealing with insurance claims, and seeking emotional support, there is also the issue of air quality, which may be more pressing than anyone realized. According to a recent study published in the journal JAMA Neurology, fine particulate matter from wildfire smoke may be linked to dementia.
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How wildfire smoke could lead to a dementia diagnosis:
For the study, which was published in November before the recent spate of fires, researchers analyzed the electronic health records of 1.2 million Kaiser Permanente Southern California (KPSC) patients between 2009 and 2018. (KPSC serves 4.7 million people across 10 California counties, including Los Angeles, where wildfires are common.) The patients were age 60 or older and did not have a prior dementia diagnosis.
More than 80,000 people were diagnosed with dementia by the conclusion of the study, supporting the hypothesis that those exposed long-term to wildfire-generated fine particulate matter (PM2.5) had an increased incidence of cognitive decline.
It should be noted that PM2.5 refers to the size of the particulate matter—in this case, 2.5 microns or less in diameter, according to the California Air Resources Board (CARB). These harmful particles typically make their way into outdoor air via car emissions and the combustion of gasoline, oil, diesel fuel, or wood in factories.
However, the JAMA study found that PM2.5 particles generated from wildfires are particularly dangerous, as those exposed to PM2.5 from other origins had a much lower increase in their dementia risk.
"We have this aging population, and we have strengthening climate change, and those may converge for really bad neurological health outcomes," said Joan Casey, the study's lead author and an associate professor of environmental and occupational health sciences at the University of Washington, in speaking with The Washington Post.
CARB explains that once inhaled, particulate matter can be "deposited on the lung surface," which can "induce tissue damage and lung inflammation." But this new research shows how air pollution can also affect the brain.
Jacques Reis, a neurologist and professor of environmental medicine at the University of Strasbourg who was not involved in the study, told The Washington Post that air particles can cause inflammation in the brain as well as neuron and DNA damage.
"[Particulates] will trigger a lot of modification at the cellular level and it’s why this is a risk factor for neurodegenerative disease," he explained.
Other researchers have made similar claims. For example, a 2015 study published in Environmental Health Perspectives found that long-term exposure to PM2.5 led to increased diagnoses of dementia, Alzheimer’s disease, and Parkinson’s.
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How you can protect yourself from wildfire smoke:
The bad news is that, according to a 2024 report produced by the nonprofit Resources for the Future (RFF), "Wildfire smoke frequently causes particulate matter pollution to exceed federal standards, and these smoke impacts are expected to grow over the century as the climate warms."
But the good news is that there are steps you can take to protect yourself from the harmful and residual effects of wildfire smoke.
Following the L.A. fires earlier this month, Cedars-Sinai recommended that those in the area wear masks outdoors for several weeks, even if their phones don't classify the air as "unhealthy." Weather data doesn't measure tiny particles, and shifting wind patterns can quickly change the air quality.
"People may think, 'Well, I don’t see or smell smoke anymore, and it looks sunny like it normally does in Southern California,' and be lulled into thinking everything is fine," said pulmonologistJeremy Falk, MD, an associate professor of Medicine at Cedars-Sinai. "But much of what can harm us in situations like this doesn’t have an odor. The Air Quality Index system was developed for everyday pollution, and not necessarily to warn us about particles that are not typically in the air because of wildfires."
Falk says an N95 mask if your best line of defense: "What makes the air pollution associated with fires so dangerous is that the particles that seem to do the most damage are much smaller than even the microscopic droplets we saw with COVID-19. Because the particles are so tiny, they can fit between the fibers of a simple paper mask or cloth mask and get far down into our airways, causing damage."
Other ways to stay safe include keeping your home's window closed and ensuring your air filtration systems (both in the home and car) are up to date.
