@xhcui
I am unable to comment at all on hazards or potential health effects of exposure to dust from abraded fiberglass. That research may exist but I am not familiar with it.
I do have good familiarity with general research on abrasion and simulated mechanical wear of polymer composites, a class of materials that would include fiberglass. That research may not be directly relevant to the application you described in your post, but generally speaking such processes do liberate substantial quantities of composite particles, and those particles frequently have the embedded fibers/materials protruding out from the surface of the particles. (Imagine concrete blocks at a demolition site with rebar sticking out.) Free fillers/fibers have also been found. Much of that work is accomplished by abrading the materials under controlled conditions in environmental and analyzing collected aerosolized and deposited dust using electron microscopy. The characteristics and number of abraded particles depend on numerous factors including the energy input, force directionality and duration, temperature, and nature of the material. Regardless of the conditions, abraded particles may or may not be hazardous to touch, inhale, or ingest - but were it me I would take sensible precautions to limit exposure where I could, particularly if this was something I would be doing a lot of.
I imagine you could search google scholar to turn up occupational safety studies more specific to your application, and I would bet there has been done some research on potential hazards and health effects.