Should I be concerned about respiratory hazard from leftover/lurking silica sand from abrasive blasting (sandblasting)?
Silica becomes a hazard with long term exposure.  Wear a mask, face shield and gloves while blasting.  Clean up and you are fine afterwards.  A small amount of exposure will not affect the vast majority of people.  If you have asthma you might want to be a little more aggressive on the clean up.