Do 3D printers release microplastics? yes, that's a fact. See for example this paper:
https://pubs.acs.org/doi/10.1021/acs.est.9b04168

As we don't know yet if they are an health issue or not, better to be little bit cautious about the 3D printing environment.
Microplastics are little plastic particles with size below 5 millimetres. 3D printers can produce microplastics below 100 microns, and even nano plastics (below 100 nanometers).
In this video I do some experiments trying to see if a small dust sensor can help in detect some of the microplastics produced by 3D printing.
The sensor is a PM5003 attached to an arduino using Adafruit libraries:
https://www.adafruit.com/product/3686

For risk management you should:
- decrease the amount of micro plastics in the environment (HEPA filter and fresh air)
- decrease your exposure, don't be in the same room while printing
- don't print exotic materials

In a following video I will try to visualise the particles using a fluorescence microscope.

Music used
Summit - by Jonny Easton
Link: https://youtu.be/ZH5B_C8r9Dk
Check out his channel
Link: https://www.youtube.com/jonnyeaston