Is it fine white powder? (No, I am not implying Canon or the retailer are involved in drug trafficking!)
I have seen this before. It is from some sort of low-density plastic or rubber, from what I gather, probably as an agent to keep it dry enough not to harbour fungus (think talc). From what I have read, it being of the amount that it is visible is rare (perhaps limited to a particular batch), but is also quite stationary and "stuck" to the surface upon which it sits. I guess it isn't a good idea to throw your lenses around, which would likely loosen it, but that probably applies white dust or not.