Its alright as long as it stays bonded to resin (like fiberglass resin, its usually within a binder) its the tiny fibers that can come off if its cut/sawed/ground that pose the major (and downright nasty) hazard.
Pretty distressed atm, because I can't find a certain erlenmeyer (flat bottomed, conical type) flask of mine. The contents of it were made with something very, very hard to get, and even harder to get safely (its not illegal just watched like a hawk from most sources) theres only one place I can get replacement supplies now, and of what I have, I'm down to maybe 100ml or less, plus some of what I made with it and then have to subject to a further reaction to get the intermediate for what I want. And the intermediate for my (belated, and indeed only, birthday treat of any kind I've, well not got, but would get. if I don't find it, my last birthday, I'd have got nothing at all a) and am pretty distressed right now because I can't find it anywhere and I put weeks of work into replacing what my stupid cunt father destroyed and refused to replace (the glassware it was in alone cost me £120-125). I've not given up, I've kept at it, and now its fucking vanished:()
I used almost the very last of what is ALMOST irreplaceable to make its replacement too, I've barely any left. Some of an intermediate, but of the chemical in question, I can only just get it from the one supplier and that isn't easy. I have enough for one more attempt, not counting the intermediate that I have to clean up first then lose some in the reaction to replace what I can't find:( and thats if I do every step perfectly.
