There are elevated lead levels around "civilization" due to human activity. (Lead paint, tetra-ethyl lead in gasoline, pesticides, etc). Food crops vary in the degree to which they accumulate lead, but they do. In general, the skin of roots and tubers have the higest levels and fruits the lowest. Keep in mind though, stems and leaves can have higher levels, particularly since various members of the mustard family (which includes broccoli, cauliflower, brussel sprouts, etc) are deliberately used for phytoremediation of lead.