Captain - relax - you can put your HS chemistry book away now. J-o-k-e. They put (only) water to keep the dust from sweeping down.

Here's a real ghastly one though: about ten years ago, up around Truckee, California the local county was trying to come up with a solution for road ice other than salt (which was killing the nearby trees and foliage) and actually tested cattle piss on a small portion of road as an alternative. The proponents stated that it has some kind of natural de-icing quality to it (break out your HS biology and chem books again).

Imagine driving through THAT. Needless to say the program was, to the total dismay of the tree-hugging greens, discontinued on the basis of protest (though it DID work remarkably well).