I have run into some of the woes of contaminants in food when growing my garden- it is nearly impossible to get compost that isn't contaminated (to the point of my husband picking up wild game from a local taxidermist and composting it with woodchips to at least get around lot of them), then when processing things from the garden, like say tomatoes, all the food processing equipment is made with plastic and aluminum unless you pay fortune and even then it can difficult to find materials that are 100% a-ok. Similarly, my husband raises pigs and chickens, there water and food supply has all these same challenges.