I highly doubt that. Soil, skin and pollen are usually the big ones. Hairs depending one how you count dust, but eliminating hair like fibres would also eliminate most of the sources of plastic, unless you allow really large particle sizes.
[edit] Checking research. The highest claim I found was 39% of fibres (in household dust, Japan). but that seemed to be per particle not by volume.
>eliminating hair like fibres would also eliminate most of the sources of plastic
If you allow fibres they'd be 0.01% of fibres if you've got a dog anything like mine.
One of the sources of intentionally manufactured microplastics are known as porous polymers in fine mesh sizes.
This is over a $1 billion market and growing.
One of the pharmaceutical uses is precisely as a medium to deliver oral medications in a time-release way.
https://www.linkedin.com/pulse/porouspolymer-bead-real-world...
These porous polymer powders consist entirely of microscopic little sponges where they soak up and/or leach out all kinds of chemicals more so than the plain polymer, and with different affinity too.
However, even when common waste plastic particles themselves are not microscopically porous, different plastics soak up different chemicals to different degrees depending on what type of contact they come into. For instance kilos of polyethylene nurdles floating in the water will actually become "soaked" with some hydrocarbon liquids that are also floating or dissolved in the water. Even physically softened. These are very solid pea-sized beads that are not micro-sized plastics at all. They would have to degrade a whole lot before they fall into the micro category. And they are not manufactured to intentionally have a nano-porous structure like the finer mesh porous polymer powders.
Chemicals and plastics just don't go away so safely every time.