I know the media itself is a respiratory hazard while blasting (I'm told the silica sand itself breaks apart from the blasting and becomes dust-like). The area will be ventilated. However, I worry about whether this hazard will remain or spread, and for how long. Would cleaning the area with large amounts of water help mitigate this issue?
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.