Any relatively soft cleaning rod can become contaminated with embedded grit. I suspect the biggest problem isn't metal shavings, but airborne dust, primarily silicates (from soil/sand/clay), which are harder than steel. Obviously, this problem is going to be worse in Iraq or Afghanistan than it is stateside, but dust is everywhere to varying degrees. It's probably not a bad idea to wipe the cleaning rod with a lightly oiled cloth before each use to remove the dust.
The worst ones are segmented aluminum rods, though. Aluminum oxidizes quickly upon contact with oxygen, forming a hard aluminum oxide layer that is far more abrasive than aluminum metal.
As to using steel-jacketed ammunition, the alloy used is very soft and not abrasive. Habitually shooting dirty/dusty ammunition could potentially increase wear, though.