Yves here. Hopefully some will find this post on the dangers of PM2.5 pollution to be useful. Air quality is one of the main reasons I live in an infamous coastal city as opposed to glamorous Bangkok. 9+ months of the year the prevailing winds come in from the sea and PM2.5 levels are low. The times when they aren’t generally are also when it’s so hot that at least occasional air con is necessary, so keeping windows closed and an air filter on isn’t a hardship.
IQ Air provides maps of air quality readings updated hourly even in secondary cities, so you can get an idea of what your ‘hood is like if you don’t want to run out and buy a PM2.5 monitor. From my general area (conditions worse today than a week ago when most stations were green; we are getting into high season, so much more traffic, and also crop burning times). You can see it is pretty granular:
You can zoom in too. This is just one notch bigger. The little arrows show the wind is coming from the sea. One monitoring post is close to me so these maps offer a good approximation:
PM2.5 actually increases with elevation at urban-type heights (tall buildings), so being on an upper floor is of no benefit.
Now to the main event.
By Paula Span. Originally published at KFF Health News
For years, the two patients had come to the Penn Memory Center at the University of Pennsylvania, where doctors and researchers follow people with cognitive impairment as they age, as well as a group with normal cognition.Both patients, a man and a woman, had agreed to donate their brains after they died for further research. “An amazing gift,” said Edward Lee, the neuropathologist who directs the brain bank at the university’s Perelman School of Medicine. “They were both very dedicated to helping us understand Alzheimer’s disease.”
The man, who died at 83 with dementia, had lived in the Center City neighborhood of Philadelphia with hired caregivers. The autopsy showed large amounts of amyloid plaques and tau tangles, the proteins associated with Alzheimer’s disease, spreading through his brain.
Researchers also found infarcts, small spots of damaged tissue, indicating that he had suffered several strokes.
By contrast, the woman, who was 84 when she died of brain cancer, “had barely any Alzheimer’s pathology,” Lee said. “We had tested her year after year, and she had no cognitive issues at all.”
The man had lived a few blocks from Interstate 676, which slices through downtown Philadelphia. The woman had lived a few miles away in the suburb of Gladwyne, Pennsylvania, surrounded by woods and a country club.
The amount of air pollution she was exposed to — specifically, the level of fine particulate matter called PM2.5 — was less than half that of his exposure. Was it a coincidence that he had developed severe Alzheimer’s while she had remained cognitively normal?
With increasing evidence that chronic exposure to PM2.5, a neurotoxin, not only damages lungs and hearts but is also associated with dementia, probably not.
“The quality of the air you live in affects your cognition,” said Lee, the senior author of a recent article in JAMA Neurology, one of several large studies in the past few months to demonstrate an association between PM2.5 and dementia.
Scientists have been tracking the connection for at least a decade. In 2020, the influential Lancet Commission added air pollution to its list of modifiable risk factors for dementia, along with common problems like hearing loss, diabetes, smoking, and high blood pressure.
Yet such findings are emerging when the federal government is dismantling efforts by previous administrations to continue reducing air pollution by shifting from fossil fuels to renewable energy sources.
“‘Drill, baby, drill’ is totally the wrong approach,” said John Balmes, a spokesperson for the American Lung Association who researches the effects of air pollution on health at the University of California-San Francisco.
“All these actions are going to decrease air quality and lead to increasing mortality and illness, dementia being one of those outcomes,” Balmes said, referring to recent environmental moves by the White House.
Many factors contribute to dementia, of course. But the role of particulates — microscopic solids or droplets in the air — is drawing closer scrutiny.
Particulates arise from many sources: emissions from power plants and home heating, factory fumes, motor vehicle exhaust, and, increasingly, wildfire smoke.
Of the several particulate sizes, PM2.5 “seems to be the most damaging to human health,” Lee said, because it is among the smallest. Easily inhaled, the particles enter the bloodstream and circulate through the body; they can also travel directly from the nose to the brain.
The research at the University of Pennsylvania, the largest autopsy study to date of people with dementia, included more than 600 brains donated over two decades.
Previous research on pollution and dementia mostly relied on epidemiological studies to establish an association. Now, “we’re linking what we actually see in the brain with exposure to pollutants,” Lee said, adding, “We’re able to do a deeper dive.”
The study participants had undergone years of cognitive testing at Penn Memory. With an environmental database, the researchers were able to calculate their PM2.5 exposure based on their home addresses.
The scientists also devised a matrix to measure how severely Alzheimer’s and other dementias had damaged donors’ brains.
Lee’s team concluded that “the higher the exposure to PM2.5, the greater the extent of Alzheimer’s disease,” he said. The odds of more severe Alzheimer’s pathology at autopsy were almost 20% greater among donors who had lived where PM2.5 levels were high.
Another research team recently reported a connection between PM2.5 exposure and Lewy body dementia, which includes dementia related to Parkinson’s disease. Generally considered the second most common type after Alzheimer’s, Lewy body accounts for an estimated 5% to 15% of dementia cases.
In what the researchers believe is the largest epidemiological study to date of pollution and dementia, they analyzed records from more than 56 million beneficiaries with traditional Medicare from 2000 to 2014, comparing their initial hospitalizations for neurodegenerative diseases with their exposure to PM2.5 by ZIP codes.
“Chronic PM2.5 exposure was linked to hospitalization for Lewy body dementia,” said Xiao Wu, an author of the study and a biostatistician at the Mailman School of Public Health at Columbia University.
After controlling for socioeconomic and other differences, the researchers found that the rate of Lewy body hospitalizations was 12% higher in U.S. counties with the worst concentrations of PM2.5 than in those with the lowest.
To help verify their findings, the researchers nasally administered PM2.5 to laboratory mice, which after 10 months showed “clear dementia-like deficits,” senior author Xiaobo Mao, a neuroscientist at the Johns Hopkins School of Medicine, wrote in an email.
The mice got lost in mazes that they had previously dashed through. They had earlier built nests quickly and compactly; now their efforts were sloppy, disorganized. At autopsy, Mao said, their brains had atrophied and contained accumulations of the protein associated with Lewy bodies in human brains, called alpha-synuclein.
A third analysis, published this summer in The Lancet, included 32 studies conducted in Europe, North America, Asia, and Australia. It also found “a dementia diagnosis to be significantly associated with long-term exposure to PM2.5” and to certain other pollutants.
Whether so-called ambient air pollution — the outdoor kind — increases dementia because of inflammation or other physiological causes awaits the next round of research.
Although air pollution has declined in the United States over two decades, scientists are calling for still stronger policies to promote cleaner air. “People argue that air quality is expensive,” Lee said. “So is dementia care.”
President Donald Trump, however, reentered office vowing to increase the extraction and use of fossil fuels and to block the transition to renewable energy. His administration has rescinded tax incentives for solar installations and electric vehicles, Balmes noted, adding, “They’re encouraging continuing to burn coal for power generation.”
The administration has halted new offshore wind farms, announced oil and gas drilling in the Arctic National Wildlife Refuge in Alaska, and moved to stop California’s plan to transition to electric cars by 2035. (The state has challenged that action in court.)
“If policy goes in the opposite direction, with more air pollution, that’s a big health risk for older adults,” Wu said.
Last year, under the Biden administration, the Environmental Protection Agency set tougher annual standards for PM2.5, noting that “the available scientific evidence and technical information indicate that the current standards may not be adequate to protect public health and welfare, as required by the Clean Air Act.”
In March, the EPA’s new chairman announced that the agency would be “revisiting” those stricter standards.
Paris. 8;11 am
Why I like NC: From Quora
“Ukraine’s Main Intelligence Directorate (GUR) reports that the Russian army is disintegrating due to widespread negligence, substance abuse, and poor living conditions. Over 600 soldiers from Russia’s Central Military District have died between 2024 and 2025 from alcohol and drug overdoses, fights, and unsanitary environments.
The intelligence report highlights a sharp rise in suicides and drug-related deaths. At least 71 Russian soldiers took their own lives in 2024, with 86 more suicides already recorded in the first half of 2025. Drug poisoning has claimed 112 lives so far this year, nearly matching last year’s total of 143.”
So, I love you guys
Well the US military must be in deep trouble. It had 523 suicides in 2023 (last complete year of data) and we are not in any ground wars:
https://www.war.gov/News/Releases/Release/Article/3964785/department-of-defense-releases-its-annual-report-on-suicide-in-the-military-for/
Feels free to move or delete the comment….It’s off topic. And just another unsupported opinion.
But seriously…I though quota ppl were supposed to be intelligent.
Having an air monitor (indoors and outdoors) made me more anxious about the air I breathe than ever! I note that the air quality in Australia generally much better than in the European continent (at least by looking at the IQAir index of main cities worldwide). My outside air monitor is on one of the islands between England and France facing south by the sea. I am baffled to see quite high reading almost everyday if the wind blows from the south (from the sea). I am thinking it might be the sea salt particles that make it high? Or maybe the dirty air from Frances reaches my monitor? It’s a mystery I’m trying to solve!
Also to note, I’ve got two indoor air monitors side by side: one is IQAir (German/Swiss made)and another one is QingPing (Chinese). Both were bought about 8 months ago, so quite up to date. Chinese monitor seems to be more advanced (it shows eTVOC as well as PM particles and CO2) and gives higher PM particle reading than IQAir. Not sure which one to trust more.
I bought two air filters from the same supposedly good company. They read PM2.5 and display their take on air quality and crank up to higher fan speeds when warranted. Sitting side by side they gave very different readings! I returned the more permissive one.
Cargo ships are infamous for polluting emissions caused by their reliance on diesel and heavy fuel oil. Perhaps you are getting whiffs of smoke from the funnels of the many ships passing through the English Channel?
If you think PM2.5’s are dangerous, try the even smaller particles. This is one reason why Europes transition to diesel engines in the 1980’s and 1990’s to reduce fuel use was a terrible idea.
It’s a notoriously difficult area of study due to very high variability of different size/types of particles. There were also studies done in the 1990’s, which so far as I know were not followed up that indicated that if the particles picked up a charge (by, for example, passing a high powered electrical cable), they may be able to pick up gaseous toxins, which could be an explanation for the very slight and controversial statistical correlation between high voltage lines and some cancers. Another significant area of uncertainty is how much exposure in homes and offices correlates to outdoor measurements. It’s worth pointing out that a huge source of domestic PM2.5’s is open fires and gas cookers. This may be why we don’t see a huge difference in diseases caused by air pollution between urban and rural areas.
One can only wonder the damage done in many developing countries as PM2.5 levels are much higher when fuel grades are lower, which is a feature of most countries outside Europe and the US, especially in the poor countries of Asia. India/Pakistan is a particular offender in this, and Chinese gasoline quality is significantly worse than most countries of similar levels of development (although it is getting better). Incineration is also a major source and many of those countries have been going all in on incineration as a ‘solution’ to the waste problem.
Just roughly checking it out, the prevalence of asthma in kids globally is something like 14% (~13,539 per 100,000) compared to where I am with a prevalence of something like 30%, not to mention our prevalence of chronic sinusitis which I haven’t checked but also feels extreme.
A noticable number of vehicles emit either white or black smoke and plastic garbage is burnt in backyards daily so you don’t have to wonder the damage done PK, it is pretty bad. Still, even persons that are here will swear you’re fussing over nothing.
Our dementia #s as well are 5% compared to 0.7% internationally (though there are a lot of other factors affecting that and I have some reason to doubt the methodology. Even anectdotally, however, the number feels high).
Thanks. Of course if air pollution is a major source of dementia then one would conclude that most people in our USA past had it and much more so than today. There was a time when Pittsburgh had to light their street lamps during the day because it was so dark.
I have mild asthma and am very sensitive to pollutants. Back when I did a lot more camping I gave up on campfires because of the smoke. Air quality wise I’d say the eco movement has given us huge improvements in this country. But for sure the Trumpie attack on the environment may take things backwards.
I wondered about the dementia prevalence back in the day myself.
Part of it could be that 1) the populatiom was smaller but also 2) life expectancy was shorter. Alzheimers and Vascular Dementia are two of the most common types and Alzheimer’s generally happens after age 65, with the risk seeming to increase slightly each year. Vascular dementia (and Alzheimer’s as well) are related to chronic disease burden, so they’re more likely in persons with Diabetes, Hypertension etc. I believe those, from what I’m seeing anyway, weren’t as common in the US until the 60’s with the spread of cigarettes and increasingly high carb diets.
Another risk factor, specifically for Alzheimer’s, is ‘loneliness’ as in, reduced social interactions and support. Somebody who knows more history can correct me on this but there may have been more family cohesiveness in earlier years.
Finally a lot of the early signs may have been chalked up to ‘old person things’ (something that still happens) and the person ends up dying from something else before the symptoms became obvious. (As a side note, memory loss and slowing of processing speed can happen during aging but it shouldn’t be particularly significant. I know health insurance is crap but it wouldn’t hurt to get checked for dementia (can be done with a 30 item questionnaire) if memory/behaviour really starts changing, if possible).
Definitely a good point though and I think it also highlights that air pollution alone isn’t likely to be sufficient. Though it seems it does increase the risk, a couple of other things still have to go wrong.
Whilst I get the gist of the post the endless and increasing back ground toxification of the environment is only accelerating. How that squares with economics and social constructs is a slow process.
Sequoia NP always has the worst air quality of any National Park, and luckily i’m inoculated from its effects mentally, through acquired immunity from growing up with horrendous LA smog in the 60’s and 70’s.
My front doorstep was a straight shot 10 miles across the San Gabriel Valley view of the San Gabriel mountain range, and i’d see it maybe 2 or 3x a year, always after a healthy rainstorm, and then the smog would return and close ranks.
Isn’t L.A. much like Phoenix in that it sits in a bowl of mountains? Air quality in that latter is getting worse as more people crowd in.
I think the most polluted place I’ve ever been was Mexico City back in the 70s–more bowl effect.
I remember being amazed at how smoggy of a place Denver was back in the day, but the same dynamic, in a bowl set against a mountain range.
The Sandias trap the smog in Albuquerque as well.
Hence why in the 80s some considered everything East of PCH/405 non Calif. Just due to Sea Breezes keeping the industrial/sprawl pollution on the other side of the 405 with a side of Bch culture/lifestyle thingy. It was sort of funny how, not unlike Musk’s EV tax credit scam parallels how pollution credits were used by big emitters in L.A. back in that time. Major polluters just bought them off lots of randoms and never skipped a beat.
I know what Wuk means as I had to do businesses in Glendale near the Observatory a few times. Around 12 noon its like someone is playing with the sky dim knob, till your lucky to see a stop sign not far away.
In Denver’s case, back in the day its was old style wood burning fire places until the ban. Also it altitude, Mountains, with an inversion layer over the whole thing. Luckily here in Brisbane its only a factor when bush fires are in play.
I wish you guys would keep it quite about the PM2.5 problem. It’s only a matter of time until some billionaire gets the bright idea to scale up air filters to the size of shipping containers so that they can be deployed all around the world to solve this problem. So invest your money now and get in on the ground floor.
This is suppose to be satire but these days, if this happened, I would not be surprised at all. But I do wonder at the aftermath of all those massive fires breaking out all around the world and all the smoke generated with all sorts of particle matter carried in them.
Prometheus did us no favors when he traded us internal combustion engines for our horses.
I see the citizens of Dehli are choking on AQIs over 400.
Wildfire smoke won’t be going away anytime soon. Same with cars and gas grills.
I wonder if getting Alzheimer’s is like being expelled from the present, cursed to forever wander the dusty chambers of memories long ago.
You’re describing my typical Spotify listening experience. ;) You’re right about Prometheus. Some people point at agriculture, others at language. We were “altering” ecosystems with fire well before the ICE. (Remember when the internal combustion engine was what “ICE” was used for?)
As Yves talks about, “burning season” is still very much a thing in Thailand. My son hates it more than monsoon. And we seem to have adopted the practice here and in Canada, though it can’t claim an agricultural purpose in North America.
Excellent walk-through and explanation by neuroscientist Tim Cheung of the Lewy body dementia paper here: https://www.microbe.tv/twin/twin-065/
The full preprint of the Science article is here: https://pmc.ncbi.nlm.nih.gov/articles/PMC12459341/
There is a related issue about aluminum nano-particle spraying by jets for cloud seeding. Some states like Florida and Wyoming have taken steps to restrict that spraying. All concerning if you live on a flight path.
Articles are on the geoengineering watch website.
PM2.5 is the wrong parameter for health, its really PM0.1; however analyzers to measure it are very very expensive, which is why the EPA set on PM2.5.
These very small nano particles get very deep in the lungs with month long clearance times, they are able to cross all body barriers (if 30 nm or smaller), and the immune system attacks the particles and tissues around the particle. Hence air pollution health impacts mirror many of the Covid19 health impacts. Of course where the two occur simultaneously, disease incidence is higher. I was able to show the COVID incidence in LA increased significantly the week after the wildfire smoke.
This author links serial killers in the Pacific Northwest to industrial polution.
Murderland