But it is a special dust that serves a special purpose. Let's take "Arizona dust" as an example. This is dust with a defined composition (modeled on Arizona road dust) that is needed for the standard-compliant testing of air filters for car engines in accordance with ISO 12103-1. And "synthetic house dust" is used for testing household vacuum cleaners in accordance with the standard.
So anyone testing vacuum cleaners or air filters needs such dusts. This is a niche market, for example for TÜV Nord, which offers around sixty types of test dusts and sells no less than eight tons of such dusts every year, which are not easy to produce because they are made entirely of artificial materials. The aim is therefore to replicate the "natural" dust as closely as possible in terms of its composition and properties.
This means that the production and sale of dusts is a complex matter and a serious business, which other suppliers such as KSL Staubtechnik and PTI/Fiatec have mastered in addition to TÜV Nord. If you need standardized dust, you can visit their homepages and webshops.
Here is the link to three suppliers of test dusts:
https://www.ksl-staubtechnik.de/branchen_produkte/pruefstaub-teststaub/normstaeube/
https://testdust.dmt-group.com/normstaeube/
https://www.fiatec.com/PTI-Pruefstaeube/iso-test-staub-produkte_1
And here is an explanation by an expert from TÜV Nord why test dusts are needed and how they are produced:
https://www.tuev-nord.de/explore/de/erklaert/was-sind-pruefstaeube/