They don’t need to be filtered. They get trapped in mucus. The constant flow of mucus from all your mucosal membranes pushes these outwards.

In the case of your lungs they get delivered to the great acid bath that is your stomach.

This. We evolved in an environment with plenty of particulate matter. It's the exotic stuff that has no analog from the time when we evolved that causes problems.

As opposed to acrylic?

Without knowing for sure, I imagine acrylic to be inert and most like any other dust on the time scale it takes for our bodies to expel it. But I could be wrong. Certainly, there are modern dangerous materials which do affect us, such as asbestos and heavy metals.

Fiberglas is listed in the US anyway as a carcinogen.

Interesting that fiberglass fibers are typically 5-25 micrometers (µm), while asbestos fibers can be 180A to 300A (1 angstrom = 1/10000th of a micrometer. So an asbestos fiber is between ~200 to 1400 times smaller than a glass fiber.

Acrylic fibers are 15 µm to 25 µm. Merino wool fibers are 15 µm to 30 µm. And human hairs diameters are between 20 to 200 µm.

Seems to be a biological limit to the body cleaning system e.g. nanoparticles, abestos

It all depends on how well your body is able to clean them out and what it does if it remains. Asbestos isn't bad because it's a fiber it's bad because it is hard for your lungs to move and damages the interior.