Hi Jeff,
I use my blaster for a bit of a specialized application on stainless steel. The abrasive I use is iron free so it doesn't contaminate the surface. Garfield sands supply a wide range of abrasives.
http://www.garfieldsands.com.au/.
You are rightly concerned about silicosis and need to take appropriate precautions but you can use all sorts of non sand alternatives like soda, although I have not tried it personally.
Graeme