Anywhere near the rustbelt is going to need their soil thoroughly tested for contamination. But maybe that's not too big a deal when you amortize the cost over the entire life of a farm.
You do realize the rust belt is enormous and only an infinitesimally small area of it was factories, right? Sure. Don’t try to grow food in Detroit. But vast majority of PA, OH, IN, MI have always been rural and are not some polluted hell scape.
Their main point is wrong... but it is worth pointing out that a lot of the soils in the northest _do_ need to be tested not because of industrial pollution but because of agricultural pollution.
Apple orchards in particular up until the 70s often used lead arsenate pesticide sprays. Yes, you read that right; lead and arsenic. Sprayed onto plants. It accumulated in the soil and basically never leaves, and is a serious potential health hazard.
There has been insufficient discussion of this, overall, and it's basically "buyer beware" for land.
Not to mention the tremendous farmland in Wisconsin and Iowa that could easily be converted to vegetable farms if the demand shifted from animal product.