It's feasible. Perhaps not for everyone. If you're serious about this (and I don't think you ought to be) the only way you're going to control it is by making

It's feasible. Perhaps not for everyone. If you're serious about this (and I don't think you ought to be) the only way you're going to control it is by making sure the land your food comes from is accountable to you. You can certainly find out whether the agricultural land your food is grown on was once something else. You can certainly reasonably guess if there may be high concentrations of pollutants deposited in the soil by examining the history of the land. Maybe the land being used was once near heavy industry, maybe it was a site that once heavily used insecticides, etc. For example, perhaps the farmland you're looking at is adjacent to an interstate. Leaded gas used for decades will have polluted the topsoil to a greater extent here than on other, more remote, land. You could choose not to buy produce from the interstate farm. This is easy enough to do. Sourcing is one of the most basic skills people ought to have. I don't think people ought to be worried and go out of their way, to be honest. A great way to do this at home is to grow your own produce in raised garden beds with good, clean, fresh, topsoil.