Mining can be a dusty process. Between the dust caused by the crushing of material and the dust caused by trucks carrying away heavy loads of the material, it's not unusual for there to be some impact on neighboring property owners.
One of the regulations that mining operations have to comply with in the state of Iowa involves making sure what the Iowa DNR describes as "fugitive dust" is kept below certain levels. What constitutes "fugitive dust" and what are acceptable levels of the dust are questions that the DNR is in charge of answering.
If you raise the issue of dust with county officials, they will tell you "The DNR is in charge of that."
But an interesting thing has happened in Des Moines. Funding for this program of the DNR has been cut to the point where there are only four inspectors of "fugitive dust" for the entire state. So if you ask the DNR to bring their equipment to test dust levels, they tell you they aren't able to do that.
This is the game that politicians of all stripes sometimes play. They will pass legislation designed "to do something about dust issues," and then will quietly forget to appropriate money to make sure the legislation gets enforced. That way they can have it both ways--they can say they're "cracking down on dust control" at the same time they're making sure they aren't.
A law, it seems, is only as good as the enforcement of the law can be.