| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Brassica oleracea | Stem | -- | 3.61 | * | |
| Brassica oleracea var. capitata l. | Leaf | -- | -- | * | |
| Armoracia rusticana | Root | -- | -- | Newall, C. A., Anderson, L. A. and Phillipson, J. D. 1996. Herbal Medicine - A Guide for Health-care Professionals. The Pharmaceutical Press, London. 296pp. |