Silicosis? Lung condition?
Yes, a lung respiratory disease.
First signs are pain in your lungs. Ask me how I know. I stopped using sand long ago.
What happens is that when the sand hits metal at high speed, it fragments. Some turns into dust. The dust has sharp edges that connect onto your lung sacs inside your lungs.
My preferred method now of blasting is to remove paint first with paint remover. Srape and clean off.
Then blast. Way less work in the long run done this way. Also less chance of sheet metal warpage besides since you won't be putting as much effort of stripping in any particular area.