[HN Gopher] Studies increasingly find links between air pollutan...
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Studies increasingly find links between air pollutants and dementia
Author : quapster
Score : 113 points
Date : 2025-11-01 16:54 UTC (6 hours ago)
(HTM) web link (www.nytimes.com)
(TXT) w3m dump (www.nytimes.com)
| mackeye wrote:
| https://www.nytimes.com/2025/11/01/health/alzheimers-dementi...
| crazygringo wrote:
| > _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._
|
| PM2.5 is not a neurotoxin, that's an absurd thing to say.
|
| It's literally _any_ particles under a certain size. Whether it
| 's a neurotoxin is necessarily going to depend on what the
| substance is made of.
|
| Whether your PM2.5 exposure is coming from automobiles or
| wildfires or a factory, the potential outcomes may be different
| in different areas of the body. Heck, my PM2.5 meter skyrockets
| whenever I cook anything in a frying pan, because many of the
| aerosolized oil droplets are PM2.5.
| epistasis wrote:
| Frying pan PM2.5 is pollution, and has been linked to increased
| childhood asthma, on of the easier and more immediate readouts
| from exposure. Linking dementia to that is a far harder
| scientific task due to the amounts of exposure and variability
| over time. Here's one blog post going over some of the evidence
| linking gas stoves to asthma:
|
| https://www.health.harvard.edu/blog/have-a-gas-stove-how-to-...
| blueflow wrote:
| How is that related to what GP wrote?
| epistasis wrote:
| That poster seemed to be saying that frying pan PM2.5 was
| not a health risk:
|
| > Heck, my PM2.5 meter skyrockets whenever I cook anything
| in a frying pan, because many of the aerosolized oil
| droplets are PM2.5.
|
| I'm not sure how they determined that PM2.5 is not a
| neurotoxin, or the full extent of their claims, but frying
| pans inside are a common cause of minor health problems.
| blueflow wrote:
| The point was that PM2.5 is a measurement of particle
| size, and that by itself allows no judgement about its
| toxicity. The same way you cannot argue that things of 5
| centimeter diameter are healthy.
|
| The toxicity judgement comes from the information _what_
| substance has the form of PM2.5, and the journo managed
| to omit that.
| epistasis wrote:
| > The point was that PM2.5 is a measurement of particle
| size, and that by itself allows no judgement about its
| toxicity.
|
| This does not logically follow at all. The size indicates
| where it can reach in the lungs, whether cilia can eject
| it, etc.
|
| A 5cm ball shot at the head at high speed is indeed
| dangerous. We are talking about inhalation of particles
| causing irritation, and the size is indeed the major
| factor. Content as well, but frying pan particles filled
| with carbon chains that have gone through who knows what
| reactions are indeed of concern. Lots of extremely nasty
| things are easily accessible from chains of hydrocarbons,
| from toluene to formaldehyde.
|
| > The toxicity judgement comes from the information what
| substance has the form of PM2.5, and the journo managed
| to omit that.
|
| I believe the journalist is not at fault here in the
| least. The scientific papers I have seen usually class
| all PM2.5 together, and perhaps by source. But the size
| itself is of great concern due to the size allowing easy
| entry to the body that is not possible for larger sizes.
| plorkyeran wrote:
| There is nothing inherently impossible about the idea
| that _all_ airborne substances of some specific size are
| harmful to breathe. It simply requires that they be bad
| because they physically fit into somewhere that shouldn
| 't have foreign substances of any kind in it rather than
| because of something specific to the substance.
| stevenwoo wrote:
| Small enough particles can easily pierce the blood brain
| barrier.
| https://pmc.ncbi.nlm.nih.gov/articles/PMC10141840/ They
| also appear to interact with human gut microbiota.
| https://pmc.ncbi.nlm.nih.gov/articles/PMC11056917/
|
| What they do there is up for further study.
|
| Many studies show a high correlation with childhood
| respiratory defects and living near roads (or even
| attending school near roads) specifically a road with
| diesel truck traffic, and a recent study showed a
| decrease in effects when air filters are installed in the
| schools.
| https://pmc.ncbi.nlm.nih.gov/articles/PMC6949366/
| Terr_ wrote:
| > That poster seemed to be saying that frying pan PM2.5
| was not a health risk
|
| They said that the category "small particles" is not
| equal to the category "neurotoxic".
|
| Much like how "Walks on Two Legs" is not "Men", there may
| be some overlap in the categories, but the first does not
| reliably indicate the second. (Or vice-versa.)
| culi wrote:
| This is what frustrates me the most about air pollution
| indexes. They all treat PM2.5 equally regardless of the source.
| Smoke from a wildfire in an industrial area is NOT the same as
| smoke from a wildfire in a woodland. Hell, even some pollen
| fragments can be PM2.5. Formaldehyde and benzene particulate
| matter should not be treated equally to pollen fragments
| readthenotes1 wrote:
| Pollen fragments are really bad for some of us....
| culi wrote:
| Of course! Different bodies have different sensitivities.
| But we're talking averages here. What's gonna cause the
| most _social_ harm
| hollerith wrote:
| OK, but wood smoke is really bad for you even if the wood is
| completely natural.
| daedrdev wrote:
| yes but smoke from any urban area will have asbestos and
| numerous other potent toxins
| culi wrote:
| Sure, but asbestos, lead, formaldehyde, benzene, etc
| particulate matters are all undoubtedly going to be more
| harmful than _most_ types of wood smoke. An urban area will
| have both wood smoke (which is often treated, possibly with
| methyl bromide) and industrial smoke. Few would deny
| breathing in campfire smoke is less likely to cause more
| immediate harm than a fire at a waste site
| oidar wrote:
| Formaldehyde and benzene are not particulates, they are VOC's
| - a very different kind pollutant.
| epistasis wrote:
| But PM2.5 from, say, a frying pan could easily contain
| abundant formaldehyde and benzene as part of the oil
| particles.
| embedding-shape wrote:
| > PM2.5 is not a neurotoxin, that's an absurd thing to say.
|
| Indeed, imagine seeing "... chronic exposure to 5 ML, a
| chemical poison, not only...". Not sure how they can mistake a
| measurement for what the _particles actually are_.
| mrob wrote:
| The "PM" in PM2.5 stands for "particulate matter", so it
| actually is a noun and not just a unit of measurement.
| notmyjob wrote:
| I don't know. Pm2.5 by definition doesn't include gasses and as
| I understand it the issue is that the particulate matter,
| whatever it happens to be, gets in the bloodstream. Is there
| any particulate matter of that size that is not neurotoxic once
| it enters the bloodstream? I don't know the answer but it seems
| like a legitimate question.
| blueflow wrote:
| Amino acids!
|
| I'm sure now some other HN poster will come up with an
| explanation how Amino Acids are still neurotoxic of some
| sort.
| tpm wrote:
| That's too easy, glutamate is neurotoxic in high doses.
| blueflow wrote:
| What about sugar?
| amluto wrote:
| One would imagine that salt spray from the ocean (which can
| easily register as PM2.5) is mostly sodium chloride, is
| rather water-soluble, and is entirely harmless in your
| bloodstream in any quantity that you could plausibly inhale.
| meowface wrote:
| Yeah, very silly statement for them to write. I wouldn't be the
| slightest bit surprised if certain pollutants in that range
| were proven or will be proven to be causing gradual damage to
| the brain but that has to be presented properly.
| tzs wrote:
| From what I've read apparently pretty much all PM2.5
| encountered by most people has neurotoxic effects.
|
| It looks like there are a couple reasons for this.
|
| 1. There are a lot of substances that are neurotoxic. Most
| things that create PM2.5 pollution will involve some of them.
|
| 2. PM2.5 is good at getting to places where the body really
| doesn't like foreign objects and so the mere presence of PM2.5
| particles can trigger responses, such as inflammation, that can
| cause neurological damage even if the particle itself is made
| of a normally non-toxic substance.
| asgraham wrote:
| I was initially skeptical of this claim because I'd previously
| learned that to cross the blood-brain barrier particles need to
| be ~200nm (PM2.5 = 2500nm). However, PM2.5 does seem to be an
| important category of particles for brain damage: somehow these
| particles can access the brain [1]. Obviously, yes, it depends
| on exactly the particle whether it will be "neurotoxic," but
| generally "unnatural" particles in the brain are not going to
| do good things. (I am not an expert in particulates) it seems
| like things larger than this don't penetrate the blood-brain
| barrier, so they can't be neurotoxic. So PM2.5 is probably at
| an intersection of large enough to be unhealthy but small
| enough that the blood brain barrier doesn't help (probably some
| evolutionary argument to be made here).
|
| [1]
| https://pmc.ncbi.nlm.nih.gov/articles/PMC9491465/#:~:text=PM...
| pedalpete wrote:
| The article does suggest the particles travel "from the nose
| to the brain", but I think that may be a bit of hyperbole.
|
| In the studies described, they weren't looking for these
| particles in the brain.
|
| There is potentially a case to be made that the particles
| result in systemic inflammation, or some other pathway which
| leads to effects in the brain, rather than a direct action.
| ahaucnx wrote:
| 100% agree. It is super important to know the composition of
| the particles.
|
| Unfortunately currently only super expensive instruments can
| measure this in real-time.
|
| This is why I believe contextual information will become much
| more important in future.
|
| Detect an indoor short PM2.5 spike around lunch time, probably
| a cooking event.
|
| Detect medium elevated levels outdoor in a city in the morning
| and late afternoons, probably traffic related smoke.
|
| I actually made a small tool to simulate different events that
| contain a quiz. Give it a try here [1].
|
| [1] https://www.airgradient.com/air-quality-monitoring-
| toolkit/p...
| malfist wrote:
| The quiz hides the chart. Makes it hard to answer
| kccqzy wrote:
| Eh I'd give the author a bit of a benefit of the doubt. It's
| probably just sloppy writing for identifying correlation but
| not causation. PM2.5 particles themselves are not categorically
| neurotoxins; they just happen to be associated with other
| neurotoxins, such that high PM2.5 is a good proxy for high
| neurotoxin pollutants.
| encoderer wrote:
| " After controlling for socioeconomic and other differences, the
| researchers found that the rate of Lewy body hospitalizations was
| 12 percent higher in U.S. counties with the worst concentrations
| of PM2.5 than in those with the lowest."
|
| Not a very powerful effect.
| xezzed wrote:
| the article is clearly a fear mongering one
| epistasis wrote:
| These sorts of pollution are largely caused by building massive
| amounts of car infrastructure and not building transit instead.
| The health effects extend beyond the direct pollution exposure to
| lifestyle things such as inactivity social isolation, and more.
|
| And yet the US largely bans healthier, denser living by law.
| Density grows out of less dense areas, and those less dense areas
| nearly all have strict density caps preventing density, as well
| as road infrastructure designed to never allow density. And the
| dense areas of the country, which already show healthier lives
| for people and longer lifespans, have similarly tight caps on
| building more density
|
| All this is to say that we have made a political choice as a
| society and are now reaping what we have sown. However we can
| choose something better for the future.
| glitchc wrote:
| Your proposal flies in the face of what people actually want.
| Everyone wants a detached home with a yard. No one wants to
| live in a condo, an oct or a quad, or even a row house, as a
| permanent life-long dream. Not the people who currently own
| detached homes and not the people looking to buy homes.
| Everyone sees high-density housing as a stepping stone towards
| detached home ownership. Detached home ownership is the dream,
| the more land it comes with, the better.
| epistasis wrote:
| If people actually wanted that, you wouldn't have to ban
| denser living.
|
| Our choices are not the result of a free market, but one
| highly constrained by land use restrictions.
|
| This is seen very clearly in housing prices. Dense living is
| hugely undersupplied, and therefore very expensive.
| mjamesaustin wrote:
| This is some suburban delusion. Do you think the people who
| own multimillion dollar condos in NYC would rather live in a
| single family home? What's stopping them?
|
| I want to be in the heart of a bustling city where I can walk
| to everything and do something different every night. That's
| not possible in suburbia.
| greenchair wrote:
| Has a lot to do with time of life too. I had similar
| feelings in 20s while single.
| tzs wrote:
| > Do you think the people who own multimillion dollar
| condos in NYC would rather live in a single family home?
| What's stopping them?
|
| They'd probably rather live in a single family home in NYC.
|
| They have to choose between contradictory desires: single
| family home over condo, but NYC over suburbs or rural.
| nurumaik wrote:
| I want to live in a condo rather than detached home. Private
| home is too much of a hassle to maintain properly and also
| less likely to have many different shops/restaurants within 5
| min walk
| ta9000 wrote:
| Most people, even in the US, don't live in detached homes
| with a yard. The amount of sprawl required to accomplish that
| "dream" of everyone living in a detached home with a huge
| yard would be a disaster for the environment and commutes.
| rufus_foreman wrote:
| In 2023, 54% of the housing units in the US were single
| family detached, https://eyeonhousing.org/2024/10/owner-
| occupied-single-famil.... I guess some of those could not
| have yards, but that is pretty rare to not have any sort of
| yard in a single family detached home.
|
| 2/3 of home buyers have single family detached as their
| preferred housing, so more people want to live in that type
| of housing than currently do so.
| dboreham wrote:
| In the area with which I'm familiar it's a
| zoning/planning requirement to dedicate some proportion
| of lot area to yard. I forget the details -- it's been a
| while since I dug into this. I think that's also why
| mother in law units became popular in some jurisdictions:
| a workaround for yard area requirements since it piggy
| backs on the existing home yard arrangement.
| gausswho wrote:
| OK. Since that's what people actually want, the market should
| work without single-family-home zoning laws and minimum
| parking requirements.
|
| Glad to see different people want different things in life.
| tuveson wrote:
| > Detached home ownership is the dream, the more land it
| comes with, the better.
|
| Not everyone wants to live in the country or the suburbs. I
| wouldn't live there if you paid me.
|
| https://www.youtube.com/watch?v=93oFXRedHy0
| analog8374 wrote:
| As a country dweller I feel the same about the city. The
| city is an ugly, noisy, filthy hive of madness.
| casey2 wrote:
| Mainly due to car industry friendly legislation and
| entitled suburbanites
| epistasis wrote:
| How funny, having grown up in a rural area, I'd never
| live one again due to the madness, filth, and ugliness! I
| hope we both have ample choices for the ways we choose to
| live.
|
| Noise in cities is mostly from cars, as is the dirt and
| death and destruction. Which is why I advocate so hard
| for allowing low car lifestyles and building, something
| that is largely banned in the US.
| antisthenes wrote:
| > How funny, having grown up in a rural area, I'd never
| live one again due to the madness, filth, and ugliness!
|
| The only reason there would be madness, filth and
| ugliness in a rural area is if you left it there, because
| you are the only one living on your property.
|
| Obviously, you have to sometimes go out into a hub of
| activity to get groceries or whatnot, but the onus is on
| you to provide evidence that those hubs are epicenters of
| madness and filth in a rural area, but not the urban
| area.
|
| Your argument makes 0 sense without any evidence.
| epistasis wrote:
| > because you are the only one living on your property.
|
| This makes me think you don't actually live in a rural
| area. It's not like you're pioneering, no connection to
| the rest of society. There's still school for the kids,
| church, stores, and yes, even neighbors.
|
| Plus, most humans find having a social life to be one of
| the greatest joys in life.
|
| I find it fascinating that you think it's acceptable to
| call cities centers of madness, filth, and ugliness, but
| think it's completely unacceptable to think that of rural
| areas. Have you actually lived in a city? Or are you just
| basing it off of perceptions you get from media?
| analog8374 wrote:
| So you traded trees for hard advocating.
| epistasis wrote:
| Plenty of room for trees once there's fewer cars. Urban
| trees are great, and plentiful when they are planned for.
| theshackleford wrote:
| As someone who was a country dweller (born and raised)
| you couldn't pay me any amount of money to return to it.
|
| It's nice we get the choice though, and I do like to
| visit it still. I could just never return to such
| isolation and poor services.
| glitchc wrote:
| Sure, that's your personal preference and to each their
| own. The market speaks otherwise. Detached homes are the
| most desirable section of the real estate market based on
| consumer surveys, see the greatest growth in value compared
| to other real estate over the medium to long term and are
| basically recession proof. Even in the financial crisis of
| 2008-2009, the average loss was 10-15% in market value,
| which was recouped over the next five years.
| epistasis wrote:
| The only consumer survey they actually reveals
| preferences is the price that people are willing to pay.
| Ask them questions in isolation and you miss all the
| implicit tradeoffs inherent to the questions.
|
| And on that front, prices in dense areas are way way
| above suburban areas. Even if you subtract the lawn.
| People will pay far far more per sqft for a home in a
| dense urban area without a lawn! Which indicates that
| dense living is far undersupplied.
|
| Not coincidentally, we don't have to ban suburban living,
| we only ban dense living. Literally anybody could buy an
| apartment building, tear it down and build a single
| family home, but how often do you ever see that happen?
| But you can't go the other direction, by law.
| daedrdev wrote:
| The market shows we do not have enough housing first and
| foremost. Many people care most of all about the cost,
| which is why people live in terrible buildings, so denser
| housing which can lower housing costs is the only real
| solution to increasingly unaffordable housing. Real
| estate is recession proof because we have effectively
| banned new housing which creates a massive rent seeking
| wealth transfer to those holding onto land simply by
| being there first
| kfarr wrote:
| > Everyone wants a detached home with a yard. No one wants to
| live in a condo, an oct or a quad, or even a row house, as a
| permanent life-long dream.
|
| This is easily disproven by the state of the real estate
| market and relative value of said urban condos to suburban
| sfh
| crazygringo wrote:
| Your comment would be a lot better if you didn't use words
| like "everyone" and "no one".
|
| You'd be correct if you referred to _some_ people, but
| acknowledged that for plenty of people, a detached home with
| a yard is the _last_ thing they want. Lawn care and home
| maintenance, no thanks. Let me just pay a fee for my share of
| building maintenance, please.
| alistairSH wrote:
| People want the single family, but they don't want to pay for
| the externalities that come with sprawl.
|
| Price in the full cost of that sprawl and it becomes less
| desirable.
| theshackleford wrote:
| I in fact want none of the things you claim. I have zero
| interest in living in the burbs, in maintaining a yard. It is
| in fact my long term dream to live in the city in my
| wonderful apartment until I cark it.
|
| How bizarre you think you can talk for literally everyone in
| existence.
| analog8374 wrote:
| Dementedness is higher in cities then, right?
|
| What differences in behavior do we see between city and rural?
| culi wrote:
| Probably not true per capita. In the suburb I partially grew up
| with they would kidnap homeless people and bus them to the
| nearest city. This is quite common throughout California and
| many red states.
|
| Suburbs have more cars per capita, more driving in general,
| more asphalt,[0] more time commuting/being on the streets to
| reach common destinations, more exposure to smoke from fires,
| and sometimes even more exposure to pollutants and pesticides
| from farming (especially if they have golf courses. Golf
| courses use about 5x more pesticides than farmland per acre).
| Suburbs also have more suicides per capita than cities
|
| [0]
| https://www.sciencedirect.com/science/article/abs/pii/S03043...
| bobthepanda wrote:
| AFAIK generally health studies don't distinguish all that
| much between urban and suburban, partially because that would
| require you to come up with a consistent definition of both;
| and even across states in the US, the definition of a "city"
| is wildly inconsistent and more a reflection however the
| politics of a place evolved.
| layer8 wrote:
| Previous discussions:
|
| https://news.ycombinator.com/item?id=45157897 (129 comments)
|
| https://news.ycombinator.com/item?id=44846164 (124 comments)
| mberning wrote:
| I think they have also done studies in rodents that show pm2.5
| diesel particulate decreases insulin sensitivity.
| moneywoes wrote:
| live near a highway and can't afford to move, any ideas what I
| should do
| hexbin010 wrote:
| Air purifiers? Winix, Conway, IKEA etc
| culi wrote:
| Air purifiers are capable of removing PM2.5. Most people can
| get one under $150. I found that unused second-hand ones are
| abundant on Craigslist, eBay, etc. Get one that doesn't have
| ozone. I found that the Winix's ozone runs even when turning it
| "off".
|
| There are reviews online that also take into account long-term
| cost (including the price of the filters themselves and how
| often they need to be replaced).
| dredmorbius wrote:
| Archive / paywall: <https://archive.is/86eOb>
| disambiguation wrote:
| I recently found this blog post about an effective DIY air filter
| - explicitly filters pm2.5
|
| https://chillphysicsenjoyer.substack.com/p/measuring-my-diy-...
|
| I built one (< $50) and I'm pretty happy with the results. As
| someone with a life long sensitivity to air quality, the air
| definitely feels cleaner.
| kccqzy wrote:
| You really don't need to DIY unless you really want to. My non-
| DIY mass produced air filter from Home Depot can filter PM2.5
| too.
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