Good find. And yes, NEVER sand or trim anything without some form of adequate respiratory protection!
And with these things it isn't enough to just use the white dust masks, you need one with a carbon filter, that can be gotten as a similar style to the regular dust mask, in grey, or you can get the larger style that's a bit more expensive.
But the one Mac found also protects your eyes, so you can see while working and not getting dust specs in your eyes that are hazardous and can cause irritation and possibly inflammation.
