Dirt/dust inside my ENGINE?!?

My car's about to hit 100,000k......I opened the hood today to put some window cleaner in the appropriate tank....and I see a layer of DUST covering the entirety of the inside of the hood/engine. I work at a place with a VERY dusty parking lot...like we pretty much park in sand and I have to get 2 car washes a week. Could this be the culprit or is it a problem with the engine itself? Thanks.