Assertion: comfrey's concentration | /r/AtLocation | root
Facets:
Source sentences:
text: Although a lot more studies still need to be performed on the safety of this herb, there seems to be evidence that the highest concentration of toxic elements is in the roots as opposed to young leaves.
text: The highest concentration is in the root, having almost twice as much as in the aerial parts.
text: Largest concentrations are found in the roots, leaves contain higher quantities of the alkaloid as they grow older and young leaves contain almost none.