Wear a good HEPA mask when you're using it. I speak from experience. Silicosis is not fun. Glass beads...last I heard glass is silica and silica is glass, as they are used the beads break down into shards which work even better than beads due to their sharp, irregular shapes, until they break down to the point where they are too small and light to work. Glass dust is glass dust. You don't want to breathe it.
Even if you use steel shot or some other media that does not break down, there are all kinds of interesting bacteria, fungi etc. living on old rusty objects. You don't want to inhale them. Your lungs are a nice warm, wet dark place, where such things like to grow if they can. Of course some people can tolerate more than others.
Those old paints were mighty toxic sometimes too.
Fresh air supply to your mask with a remote hose is best if you can be sure of an inlet location for your hose that won't be contaminated by blown dust etc. from the dust/media collector's outlet. That's what the professionals use.
Soda is excellent for soft metals like brass and aluminum or thin steel which peens and warps with sand, and sometimes even with glass beads. Too bad the media is so expensive.
Poor man's sandblaster is a siphon feed for a pressure washer. Keeps the dust down, but best done on a very hot day.