To build on this conversation, the problem is that silica can't be broken down by the body. The form as encountered in rock dust is a crystaline structure that is effectively an abrasive particle like the silicon carbide or aluminum oxide in sandpaper. That basically sits in your lungs and rubs and rubs and rubs until the inflammation and scaring develops into Silicosis. This is why respiratory protection is so important, because you don't really have the ability to get over the silica you inhale.
At the minimum wearing an N95 approved mask should be the standard, N100 obviously would be better (the number is the % particulate matter down to .3 micrometer screened in nearest whole number). The N designation is aerosolized oil-resistance, with N being not oil resistant. R and P offer progressively more oil resistance.
I've run a couple clinics on re-bolting techniques and best practices and in the slide deck I cover PPE considerations. I've also written a short primer that might be of interest to people reading this thread and worth discussing/debating.