Dust in 2006 Chevy Express

[Bill]

I bought a 2006 Chevy express Cargo Van and did some mimimal conversions to make it suitable for an extended (2+ month) trip out west I'm on. I've been driving on a number of dirt/gravel roads, and as dry as it's been, i throw up a lot of dust.

The problem is that this dust has gotten all over the inside of the van, presumeably thru the back doors.

Has anyone else had this problem, and if so, figured out how to fix it.

Thanks.

Bill