A gentle note to anyone reading, fiberglass insulation requires wearing air filters, for the same reasons noted else in this thread. Wear them expecially to cut it, but also just putting it up or working in a crawlspace with it.
That’s not what the manufacturers of modern glass fiber insulation would have you believe. Plenty of people cutting and handling it with no PPE at all in their promotional literature.
Fiberglass is at least pretty easy one to figure out. Don't have to get that stuff in your skin more than once to realize it's probably really, really bad to breathe.
My understanding is that fiberglass and mineral wool [1] are classified as skin (yes, it itches), eye, and lung irritants (coughing), but they're not carcinogenic. Considering how extremely widely they have been used for a long time, if they were we'd most likely have seen it by now.
Sure it's not good for you, so using PPE is certainly warranted, but it's on a whole different level of badness compared to asbestos.
[1] Per wikipedia, there are some varieties of mineral wool used for high temperatures (think insulating industrial furnaces and such) which are carcinogens.
