> 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.
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.
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-...
Gas stoves produce NO2, not PM2.5.
https://www.cieh.org/ehn/environmental-protection/2025/april...
Quote: Research shows cooking on domestic gas hobs can cause two of the most harmful air pollutants, NO2 and PM2.5, to exceed WHO guidelines
Frying pans produce PM2.5, gas stove or no. I am talking about PM2.5. What is your point?
The point is that your link seems to be almost entirely talking about something else (pollutants from burning gas inside, which is primarily NOx)! There is one passing mention of gas stoves producing some extra PM2.5 (which I expect will be different in composition to the PM2.5 produced in the pan) but all of the rest of it seems to be focused on the NOx
You link to a report about gas stoves not frying pans.
OH! Thank you for pointing out the error! I seem to have pasted the wrong link, and am not on my computer that I was doing the searching on before... please accept this short book chapter instead, though it is far more dry than the page I remember reading before.
https://www.ncbi.nlm.nih.gov/books/NBK385529/
Apologies!
Ah - that makes more sense.
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> Children living in households that use gas stoves for cooking are 42% more likely to have asthma, according to an analysis of observational research. While observational studies can't prove that cooking with gas is the direct cause of asthma, data also show that the higher the nitrogen dioxide level, the more severe the asthma symptoms in children and adults.
Nobody is saying frying some eggs is equivalent to sucking the tail pipe of a 50s era car. You're arguing with yourself.
Makes me wonder if cooks, who (in many countries) stand in front of a gas stove for long hours every day have a statistically higher chance of asthma?
Even worse than asthma
https://preventcancer.org/article/lung-cancer-asian-american...
> Environmental exposures, such as cooking oil fumes and secondhand smoke, have long been identified as risk factors for lung cancer among women in Asia who do not smoke
Those exposures are completely unrelated to the burner used in the kitchen.
How is that related to what GP 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.
> 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.)
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.
> 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.
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.
To be just a touch pedantic, that all particles of a certain size are harmful is a silly assertion.
Water and sugar particles, for instance, are almost certainly harmless below some reasonable threshold.
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/
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
OK, but wood smoke is really bad for you even if the wood is completely natural.
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
yes but smoke from any urban area will have asbestos and numerous other potent toxins
Formaldehyde and benzene are not particulates, they are VOC’s - a very different kind pollutant.
But PM2.5 from, say, a frying pan could easily contain abundant formaldehyde and benzene as part of the oil particles.
"could easily"
I just asked ChatGPT: when using a fry pan, does the smoke contain formaldehyde and benzene?
That is a mighty hot fry pan. The hottest cooking that I know of in common practice is "wok hei"-style from China. When you start cooking, the food rarely exceeds 230C. When you are heating the pan, the oil may exceed 230C for a few seconds. If you use a fry pan, but cook in Mediterranean-style, the temperatures are much lower."could easily"? Hardly.
Formaldehyde and benzene are to volatile to condense onto or absorb into PM2.5 particles. Cooking oil particles can contain other toxic compounds formed during heating, including polycyclic aromatic hydrocarbons (PAHs), acrolein, and various aldehydes and ketones. If formaldehyde or benzene react to form less volatile products, those reaction products might become part of particulate matter, but they're no longer formaldehyde or benzene at that point. So while cooking emissions do produce both harmful VOCs and harmful PM2.5 simultaneously, they remain distinct categories of pollutants.
They don't seem to have considered fungus spores as PM2.5 either. Seems like a single spore could cause more damage than many carbon particles.
Lumping all PM2.5 together is kind of like counting calories without considering whether they come from broccoli or corn syrup
Pollen fragments are really bad for some of us....
Of course! Different bodies have different sensitivities. But we're talking averages here. What's gonna cause the most social harm
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...
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.
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.
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.
As I understand it you are incorrect. Salt from sea breeze is pm10 not pm2.5. My information may be inaccurate but google backs it up.
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.
That's too easy, glutamate is neurotoxic in high doses.
What about sugar?
pm2.5 is a metric used in assessing air quality. Amino acid aerosols are not a source of air pollution.
amino acids droplets are pm2.5. pm2.5 refers to the particle size.
See what i wrote in the other thread... https://news.ycombinator.com/item?id=45784538
Pm2.5 is a specific particle size, yes, we do agree on that. Importantly, it is also a common measurement used in assessing air quality. In that context it is typically composed of particles from a set of common sources, like wildfires, industrial sources, automobile pollution, etc…. It is, in the context of air quality monitoring, never composed of amino acids. It seems valid to make claims about pm2.5 and health, even though the claim does not distinguish wildfire pm2.5 from pm2.5 from automobile pollution or other sources. Maybe I misunderstood you to be saying otherwise.
Yeah but which substances/sources is not given when you just say "Pm2.5". Which is what the article did. And depending on the actual substances you get different health effects or none at all.
On second thought, i think this is intentional. If scientists interpolate from well-chosen substances onto all Pm2.5, it should be provable that earths atomosphere is toxic beyond limits and uninhabitable. "We destroyed earth" sells well and would justify further research funding.
</tinfoil-hat>
Is this a bit like saying that bullets made from glass are healthier than those made of lead?
I thought some of the harm comes from the size of PM2.5 particles alone.
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...
The quiz hides the chart. Makes it hard to answer
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.
Ideally we'd move toward more source-specific or composition-specific air quality standards but that's a much tougher data and policy problem
> 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.
The "PM" in PM2.5 stands for "particulate matter", so it actually is a noun and not just a unit of measurement.
Still doesn't make sense to claim that "PM2.5" is a neurotoxin, depends entirely on what the specific particles are, not the size of them.
What is more dangerous, PM2.5 or PM10? Well, naturally, smaller particles are more harmful to humans usually, but without knowing what the particles are, it's impossible to tell. Just like "5ML is/isn't more dangerous than 10ML", it doesn't really tell us anything.
There are a lot of things wrong with this. Almost anything under 2.5nm is going to weigh <500 daltons, which will cross the blood brain barrier, allowing it to have neurotoxic effects.
They might intentionally saying that something of that size is problematic.
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.
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