Cocaine Clouds

[BananaRepublic]

I was at a forestry rally, (cars), and the dust was pretty bad at/most times and Im a bit concerned about having dust now inside my 70-200 as when move the zoom control, I forget the correct term, whilst holding it to my ear I hear a kind of gritty sound. Like wise the mode wheel and sub wheel underneath also sounds similarly gritty.

They both move freely, i.e. lens zoom and mode wheels but I am a bit disappointed that I didn't take steps to protect things more.

Is there anything to be done about this.