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What’s important to understand is that PM2.5 is not PM2.5.

It only defines the diameter of the particles but can be composed of very different elements. From salt that dissolves in the lungs to toxic metals.

Currently it is extremely difficult to get a comprehensive understanding of the health impacts of these particles.

Much more research needs to be done to understand which particle compositions and thus what sources of air pollution (eg traffic, wildfires, factories, landfills, ports etc) have what kind of health effects.

If you are interested to see an image how different PM2.5 particle look like, have a look at the photo in this blog post that one of our in-house scientists wrote [1].

[1] https://www.airgradient.com/blog/pm25-is-not-pm25/

(Edited and replaced weight with diameter)

Thanks. Unrelated, but this is the first time I grasped why electron microscopes are needed and not just some fancy tech:

> 0.3 micrometers are even smaller than the wavelength of light, which demonstrates the problem: how should we see something that is smaller than light itself?

> It only defines the weight of the particles

Diameter, not weight. PM2.5 is particles of diameter 2.5μm or less.

I've also seen studies where the toxicity per microgram varied hugely depending on whether the source was traffic, coal, or biomass burning
If I had to place bets, it would be reactive species. PAHs, alcohols, and other volatiles.
very interesting article, thanks for posting
This is an obvious third-factor for poverty and marginalization. Air pollution exposure is the most classic example of unequal protection from harm in environmental justice. Alameda county did a study on this that found as an isolated, direct-result of unequal exposure to air pollution, black people live 15 years less than white people on average in Alameda County alone.
If you could see long term PM2.5 averages and how they vary, we'd approach as a national crisis.

https://www.sciencedirect.com/science/article/pii/S266601722... (this groups methods can be substantially improved).

Having done some additional follow on work in the space -- the results definitely do not follow socioeconomic boundaries as one might expect.

Roads are a huge contributor.

I find this very hard to believe... Mind sharing that study?
Literally the poor people in London lived in the East End because it was downwind.
Yeah, that tracks with a lot of the environmental justice research
On the other hand life expectancy of richest people in US is on par with poorest in EU. (Poverty is still factor within those regions).
Recently started looking at daycares in San Diego. All the good ones near me are within a couple hundred feet of a major freeway. I can't believe people send their kids to something like that.

Intuitively, I don't mind the ones 0.5 mi away from the freeway, especially if the prevailing winds place them up-wind. I have no idea if that's correct, but it seems to me that you'd have a fairly fast drop-off in noxious substances as you move away from the freeway.

We also have this recent trend of building huge apartment complexes right next to the freeways while many of the nicer areas are given to commercial and industrial uses. Makes no sense to me.

How does a freeway compare to a lower speed but busy road?
Meanwhile, current administration gutting the clean air act: https://www.npr.org/2025/07/29/nx-s1-5463771/epa-greenhouse-...
As the sole caregiver for a father with dementia I can tell you it's a nightmare.

If you have children please, please plan for late life care. And if you're going to be caring for either of your parents start planning and build a support network. By the time I knew I needed help I was drowning. Learn how to ask for help. I thought I was a relatively progressive 50 year old man, but it turns out help is a 4-letter word.

My sympathies.

As hard as it is, supporting family members also need to learn to prioritize taking care of themselves and avoiding a spiral towards burnout. With dementia, there is often a time when the patient needs a more controlled environment with 24x7 supervision. Dementia sleep schedules and behaviors fall apart and are not really compatible with a family caregiver's own health needs.

Depending on the dementia case, risky behaviors may emerge at night, and having observant caregivers awake 24x7 may be very important. The financial picture for this is quite difficult in the US. Normally this requires a care facility at some point, as it is impossibly expensive to bring sufficient dementia care via visiting professionals.

To safely handle dementia with "sundowning" and wandering behaviors, you usually need a facility that has about a dozen residents or more. Then, budgets allow for multiple onsite staff and overnight wakeful staff. This can bring more distinct staff roles too, e.g. cooking and housekeeping versus care.

Even this may be overwhelmingly costly, to the point where the dementia ends up depleting the estate and then shifting to some kind of government support. For family or trustees managing this process, it is full of difficult decisions regarding budget and care tradeoffs. For example, do you splurge on "nicer" facilities or other caregiver factors early on, or try to reserve more funds for the inevitable crises? Dementia can be a drawn-out process, where care needs expand to a crescendo before collapsing back to hospice care, which may be more like other terminal illnesses.

You have my condolences. I helped my wife care for her late father with Lewy body dementia. I think many people recognize they may need to care for the people that raised them at some point, but the realities of the costs--both financially and emotionally--are rarely discussed. @lemonberry feel free to reach out if you need a friendly ear, my email is in my profile.

On a personal note to anyone in this situation: Do not go it alone. Being a caregiver is hard, but being a caregiver for someone with serious memory issues is brutal and requires 24/7 monitoring. Your loved one will not always cooperate. They may change into someone who does not resemble the person you knew. Many states require such persons to be homed somewhere with a 24/7 nursing staff. Plan accordingly.

One major reason I'm working extra years despite being FI is so I have money to provide for memory care for my parents if they end up needing that. They have downright nothing to their name and memory care can easily run into half a million dollars total.
Don't neglect yourself. Wishing you the best. https://www.caregiveraction.org/
My wife and I don’t have children, but my exit strategy is assisted suicide. I have no intention of living past my brain.
Your advice about planning ahead is gold.... by the time the crisis point comes, you're usually too exhausted to build that support system from scratch
> Dementias such as Alzheimer's disease are estimated to affect more than 57.4 million people worldwide, a number that is expected to almost triple to 152.8 million cases by 2050

Meaningless number. Make it % or incidence rate per 1000 or something.

57 million people? That’s not so many compared to the billion in China or India. Or is it? Compare it to cancers or car accidents.

> Make it % or incidence rate per 1000 or something.

Just type it into a calculator. The computer will do all the work.

Current world population is ~8 billion so 57_000_000 / 8_000_000_000 = 0.007125

So 0.7% or 7 per 1000 people.

The increase is almost entirely due to aging population.

"The Lancet study indicates that although the total number of dementia cases is expected to increase substantially, the percentage of the global population affected, once age-adjusted, remains nearly constant, with just a 0.1% change globally between 2019 and 2050"

Given that recent Nature paper which claims that a lithium depletion could be responsible for Alzheimer's disease, is there any mechanism that could link increased air pollution to a reduction in lithium levels?
Some research suggests air pollution may disrupt blood-brain barrier integrity, potentially affecting mineral transport including lithium, while particulate matter can also bind to metal ions in the bloodstream altering their bioavailability.
The two have been posited:

Lithium can be viewed an antioxidant – correctly or not?, I do not know.

Air pollution can be viewed as oxidative stress.

It’s interesting to search Google Scholar for “lithium antioxidant”.

Right now, most of the pollution–dementia work points more toward inflammation, oxidative stress, and vascular impacts rather than nutrient depletion
Exposure to another similar metal could in theory displace lithium in biological processes.
What's frustrating is that we already have decades of knowledge on how to cut NO2 and soot from transport and energy, but politics moves at a glacial pace while the damage accumulates
Literally car-brained.
Coal trains:

https://arstechnica.com/science/2024/07/coal-pollution-is-ki... | https://www.sciencedirect.com/science/article/pii/S001393512... | https://doi.org/10.1016/j.envres.2024.118787

Warehouses:

Air pollution impacts from warehousing in the United States uncovered with satellite data - https://www.nature.com/articles/s41467-024-50000-0 | https://doi.org/10.1038/s41467-024-50000-0

Where Warehouses Are Built, Air Pollution Follows - https://earthobservatory.nasa.gov/images/153471/where-wareho...

Impact of Warehouse Expansion on Ambient PM2.5 and Elemental Carbon Levels in Southern California's Disadvantaged Communities: A Two-Decade Analysis - https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GH00... | https://doi.org/10.1029/2024GH001091

Global air quality map: https://explore.openaq.org/

(this is why it is so important to electrify trucks and to disallow industrial and commercial parks with lots of truck traffic near residential and school areas; all of this combustion/fossil energy pollution is creating health debt that will catch up with us)

Nice to know I've got bits of tire in my brain.
Proves ULEZ is the right call.
What can I do to minimize the effects of air pollution if I have to live in a city with high pollution levels? It seems completely out of my control.
I was expecting lead to be called out. I didn't go deeper than the article, but assuming the studies mentioned had a higher average age since they were studying dementia, many of them likely grew up around cars burning leaded gasoline.
ChangeTheAirFoundation.org claims 50% of US residences have problems causing this, and worse.

Nobody thinks about the quality of their air until it's been hurting them.

I was one of many.

well, long-term exposure to outdoor air pollution already shortens their lifespan so they won't even live long enough to reach the average age for dementia
It's only been what, 20 years since we've been able to remove the lead from avgas and haven't?
Get a cheap air filter at Ikea, or in a pinch a box fan with a HVAC filter taped to it.
crbox just build boat loads of them? everywhere you're going to spend more than reasonable amount of time is worth it. filters aren't expensive, it's either they suck it or our lung suck it the rest are just talk
This would suggest that a city is a hive of insanity. The bigger the crazier.
For a brief fleeting moment, man was not plagued by indoor air pollution nor outdoor air pollution
alzheimer's, parkinson's, dementia, diabetes...all metabolic diseases caused by insulin