I have always classified myself as an urban forager. Some of the best foraging is along byways. The hedgerows including the understory provide some of the widest selection of wild food there is.
I take certain precautions. I won't pick from the verges of the A50 even though they are rich in food, and I won't pick from the wetland at the base of the old landfill site. I know some plants are better at storing heavy metals others, sea buckthorn and bulrush I am lot more picky on, than say apples and blackberries. I am not picky on idea that some animal might of peed on plant either. I eat wild fungi and I know the likes of horse mushrooms are there because of animal waste. They are infections that can caught be from fox pee but is fox going pass through a field of tesco cabbages and not cock his leg?, so whats the difference between that and wild sorrel. We wash veggies for reason, and we have easophils (sp? immune cells that batter parasites).
The world is not sterile, Mother Nature has cooties, I just like to sit close enough to see them.