There are bathroom tiles on the wall (natural stone), the bathroom tends to get pretty humid (pre-code/no ventilation, do our best to keep it low). We are seeing that a few of the bathroom tiles are beginning to flake off--there seems to be a veneer and a dusty material underneath. What's the recommended way to fix this in the short-term? (there's the systemic solution to get rid of the humidity, but during the interim we don't want to inhale this underlying tile dust). Thank you!
It appears that your wall is failing. Whatever those tile are, they weren't intended for bathroom use. You can scrap off the loose particles and then apply a thin layer of caulk or sealer to the area to prevent you from inhaling the dust. How many tiles you're taking about. Other than that, you're going to have to plan on redoing the walls. The tiles will probably continue to fail even if you improve the ventilation.