Comment by ahaucnx | Hacker News Reader

Comment by ahaucnx | Hacker News Reader

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 looks like this EUV microscope can image features that small: https://sharp.lbl.gov/

> It only defines the weight of the particles

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

Yes of course! Thanks for pointing it out. I corrected the above.

You're both right enough. Aerodynamic diameter doesn't measure the particles themselves, but how their settling velocity compares to a spherical reference ideal of a certain density (1g/cm*3) in a medium.

I don't deal with gas cleaning, but at those scales, if you work a lot with applied processes like filtration and separation, you can ballpark things like daltons with mass and size. I know I do with MWCOs.

I've also seen studies where the toxicity per microgram varied hugely depending on whether the source was traffic, coal, or biomass burning

Which source was worse?

If I had to place bets, it would be reactive species. PAHs, alcohols, and other volatiles.

Even VOC is still an open question. Are great smelling food, onions, etc bad for our lungs?

very interesting article, thanks for posting

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