Are you trying to politely tell Greg he has a dandruff problem?

After all that sweeping and blowing there will be a lot of dust in the air. Better give it a chance to settle. A trick I picked up is to place two box fans at opposite sides of your work space aimed in opposite directions. Duct tape a furnace filter over each fan's intake side and spray them with Endust. As the air circulates a lot of the fine dust will be trapped in the filters.

As for that dandruff you can always check out MedWeb.