Well, glad ya got your stuff done. Perhaps a little fine tuning will have it flowing better for you next time.
OLDRED- I stand corrected. I was mistaken about the free silica content of the coal slag. Thanks for pointing that out cranky1.
In terms of health affects, you're right- no blasting agents are "safe". I wouldn't consider black beauty a safer alternative though.
As stated in the report I linked to:
"Coal slag is the most frequently used substitute for sand in abrasive blasting (Paumanok Publications, Inc., 1992), and it was more inflammatory and caused greater cell damage than blasting sand." Just FYI.
Thanks for the other link, Jon.